experiments about diffusion

STEM Little Explorers

Knowing through exploring.

Home » Articles » STEM » STEM Science » How to Demonstrate Diffusion with Hot and Cold Water

How to Demonstrate Diffusion with Hot and Cold Water

We all need some space sometimes, right that’s true down to a molecular level. molecules don’t like to stay too close together and will try to move to less crowded areas. that process is called diffusion and we will explore all about it in this simple but revealing experiment., article contents.

What is Diffusion?

Have you ever smelled your neighbor’s lunch on your way home? Or smelled someone’s perfume minutes after that person was gone? You experienced the diffusion!

Diffusion is a movement of particles from the area of high concentration to an area of low concentration. It usually occurs in liquids and gases.

Let’s get some complex-sounding terminology out of the way. When talking about diffusion, we often hear something about the concentration gradient (or electrical gradient if looking at electrons). Gradient just means a change in the quantity of a variable over some distance. In the case of concentration gradient, a variable that changes is the concentration of a substance. So we can define the concentration gradient as space over which the concentration of our substance changes.

For example, think of the situation when we spray the air freshener in the room. There is one spot where the concentration of our substance is very high (where we sprayed it initially) and in the rest of the room it is very low (nothing initially). Slowly concentration gradient is diffusing – our freshener is moving through the air. When the concentration gradient is diffused, we reach equilibrium – the state at which a substance is equally distributed throughout a space.

It’s important to note that particles never stop moving , even after the equilibrium is reached. Imagine two parts of the room divided by a line. It may seem like nothing is happening, but particles from both sides are moving back and forth. It’s just that it is an equal probability of them moving from left to right as it’s from right to left. So we can’t notice any net change.

Diffusion is a type of passive transport . That means it doesn’t require energy to start. It happens naturally, without any shaking or stirring.

There is also a facilitated diffusion which happens in the cell membranes when molecules are transported with the help of the proteins.

You may remember hearing about Osmosis and think about how is this different from it. It is actually a very similar concept. Osmosis is just a diffusion through the partially permeable membrane. We talked about it more in our Gummy Bear Osmosis Experiment so definitely check it out.

What causes Diffusion?

Do particles really want to move somewhere less crowded? Well, no, not in the way we would think of it. There is no planning around, just the probability.

All fluids are bound to the same physical laws – studied by Fluid mechanics , part of the physics. We usually think of fluids as liquids, but in fact, air and other types of gas are also fluids ! By definition , fluid is a substance that has no fixed shape and yields easily to external pressure.

Another property of the fluids is that they flow or move around. Molecules in fluids move around randomly and that causes collisions between them and makes them bounce off in different directions.

This random motion of particles in a fluid is called Brownian motion . It was named by the biologist Robert Brown who observed and described the phenomenon in 1827. While doing some experiments with pollen under the microscope, he noticed it wiggles in the water. He concluded that pollen must be alive. Even though his theory was far off, his observation was important in proving the existence of atoms and molecules.

Factors that influence Diffusion

There are several factors that influence the speed of diffusion. The first is the extent of the concentration gradient . The bigger the difference in concentration over the gradient, the faster diffusion occurs.

Another important factor is the distance over which our particles are moving. We can look at it as the size of a container. As you may imagine, with the bigger distance, diffusion is slower, since particles need to move further.

Then we have characteristics of the solvent and substance. The most notable is the mass of the substance and density of the solvent . Heavier molecules move more slowly; therefore, they diffuse more slowly. And it’s a similar case with the density of the solvent. As density increases, the rate of diffusion decreases. It’s harder to move through the denser solvent, therefore our molecules slow down.

And the last factor we will discuss is the temperature . Both heating and cooling change the kinetic energy of the particles in our substance. In the case of heating, we are increasing the kinetic energy of our particles and that makes them move a lot quicker. So the higher the temperature, the higher the diffusion rate.

We will demonstrate the diffusion of food coloring in water and observe how it’s affected by the difference in temperature. Onwards to the experiment!

Materials needed for demonstrating Diffusion

• 2 transparent glasses – Common clear glasses will do the trick. You probably have more than needed around the house. We need one for warm water and one for cold water so we can observe the difference in diffusion.
• Hot and cold water – The bigger the difference in temperature in two glasses, the bigger difference in diffusion will be observed. You can heat the water to near boiling or boiling state and use it as hot water. Use regular water from the pipe as “cold water”. That is enough difference to observe the effects of temperature on diffusion.
• Food coloring – Regular food coloring or some other colors like tempera (poster paint) will do the trick. Color is required to observe the diffusion in our solvent (water). To make it more fun, you can use 2 different colors. Like red for hot and blue for cold.

Instructions for demonstrating diffusion

We have a video on how to demonstrate diffusion at the start of the article so you can check it out if you prefer a video guide more. Or continue reading instructions below if you prefer step by step text guide.

• Take 2 transparent glasses and fill them with the water . In one glass, pour the cold water and in the other hot water. As we mentioned, near-boiling water for hot and regular temperature water from the pipe will be good to demonstrate the diffusion.
• Drop a few drops of food coloring in each cup . 3-4 drops are enough and you should not put too much food color. If you put too much, the concentration of food color will be too large and it will defuse too fast in both glasses. 
• Watch closely how the color spreads . You will notice how color diffuses faster in hot water. It will take longer to diffuse if there is more water, less food color and if the water is cooler.

What will you develop and learn

• What is diffusion and how it relates to osmosis
• Factors that influence diffusion
• What is Brownian motion
• How to conduct a science experiment
• That science is fun! 😊

If you liked this activity and are interested in more simple fun experiments, we recommend exploring all about the heat conduction . For more cool visuals made by chemistry, check out Lava lamp and Milk polarity experiment . And if you, like us, find the water fascinating, definitely read our article about many interesting properties of water .

If you’re searching for some great STEM Activities for Kids and Child development tips, you’re in the right place! Check the Categories below to find the right activity for you.

STEM Science

Videos, guides and explanations about STEM Science in a step-by-step way with materials you probably already have at your home. Find new Science ideas.

STEM Technology

Videos, guides and explanations about STEM Technology in a step-by-step way with materials you probably already have at your home. Find new Technology ideas.

STEM Engineering

Videos, guides and explanations about STEM Engineering in a step-by-step way with materials you probably already have at your home. New Engineering ideas!

Videos, guides and explanations about STEM Math in a step-by-step way with materials you probably already have at your home. Find new Mathematics ideas.

Find out all about development psychology topics that you always wanted to know. Here are articles from child psychology and development psychology overall.

First year of Child’s Life

Following a Child’s development every month from its birth. Personal experiences and tips on how to cope with challenges that you will face in parenting.

4 thoughts on “ How to Demonstrate Diffusion with Hot and Cold Water ”

• Pingback: How to Make Colorful Milk Polarity Experiment - STEM Little Explorers
• Pingback: How to make a Lava Lamp | STEM Little Explorers
• Pingback: Learn about pressure with Can Crush Experiment - STEM Little Explorers
• Pingback: Gummy bear Osmosis Experiment - STEM Little Explorers

Leave a Reply Cancel reply

You must be logged in to post a comment.

Get Fresh news from STEM fields

I'm not interested in STEM

Your browser is not supported

Sorry but it looks as if your browser is out of date. To get the best experience using our site we recommend that you upgrade or switch browsers.

Find a solution

• Skip to main content
• Skip to navigation

• Back to parent navigation item
• Primary teacher
• Secondary/FE teacher
• Early career or student teacher
• Higher education
• Curriculum support
• Literacy in science teaching
• Periodic table
• Interactive periodic table
• Climate change and sustainability
• Resources shop
• Collections
• Post-lockdown teaching support
• Remote teaching support
• Starters for ten
• Screen experiments
• Assessment for learning
• Microscale chemistry
• Faces of chemistry
• Classic chemistry experiments
• Nuffield practical collection
• Anecdotes for chemistry teachers
• On this day in chemistry
• Global experiments
• PhET interactive simulations
• Chemistry vignettes
• Context and problem based learning
• Journal of the month
• Chemistry and art
• Art analysis
• Pigments and colours
• Ancient art: today's technology
• Psychology and art theory
• Art and archaeology
• Artists as chemists
• The physics of restoration and conservation
• Ancient Egyptian art
• Ancient Greek art
• Ancient Roman art
• Classic chemistry demonstrations
• In search of solutions
• In search of more solutions
• Creative problem-solving in chemistry
• Solar spark
• Chemistry for non-specialists
• Health and safety in higher education
• Analytical chemistry introductions
• Exhibition chemistry
• Introductory maths for higher education
• Commercial skills for chemists
• Kitchen chemistry
• Journals how to guides
• Chemistry in health
• Chemistry in sport
• Chemistry in your cupboard
• Chocolate chemistry
• Adnoddau addysgu cemeg Cymraeg
• The chemistry of fireworks
• Festive chemistry
• Education in Chemistry
• Teach Chemistry
• On-demand online
• Live online
• Selected PD articles
• PD for primary teachers
• PD for secondary teachers
• What we offer
• Chartered Science Teacher (CSciTeach)
• Teacher mentoring
• UK Chemistry Olympiad
• Who can enter?
• How does it work?
• Resources and past papers
• Top of the Bench
• Schools' Analyst
• Regional support
• Education coordinators
• RSC Yusuf Hamied Inspirational Science Programme
• RSC Education News
• Supporting teacher training
• Interest groups

• More navigation items

Diffusion in liquids

In association with Nuffield Foundation

Demonstrate that diffusion takes place in liquids by allowing lead nitrate and potassium iodide to form lead iodide as they diffuse towards each other in this practical

In this experiment, students place colourless crystals of lead nitrate and potassium iodide at opposite sides of a Petri dish of deionised water. As these substances dissolve and diffuse towards each other, students can observe clouds of yellow lead iodide forming, demonstrating that diffusion has taken place.

This practical activity takes around 30 minutes.

• Eye protection
• White tile or piece of white paper
• Lead nitrate (TOXIC, DANGEROUS FOR THE ENVIRONMENT), 1 crystal
• Potassium iodide, 1 crystal
• Deionised water

Greener alternatives

To reduce the use of toxic chemicals in this experiment you can conduct the experiment in microscale, using drops of water on a laminated sheet, find full instructions and video here, and/or use a less toxic salt than lead nitrate, eg sodium carbonate and barium chloride. More information is available from CLEAPSS.

Health, safety and technical notes

• Read our standard health and safety guidance.
• Wear eye protection throughout.
• Lead nitrate, Pb(NO 3 ) 2 (s), (TOXIC, DANGEROUS FOR THE ENVIRONMENT) – see CLEAPSS Hazcard HC057a .
• Potassium iodide, KI(s) – see CLEAPSS Hazcard HC047b .
• Place a Petri dish on a white tile or piece of white paper. Fill it nearly to the top with deionised water.
• Using forceps, place a crystal of lead nitrate at one side of the petri dish and a crystal of potassium iodide at the other.
• Observe as the crystals begin to dissolve and a new compound is formed between them.

Source: Royal Society of Chemistry

As the crystals of potassium iodide and lead nitrate dissolve and diffuse, they will begin to form yellow lead iodide

Teaching notes

The lead nitrate and potassium iodide each dissolve and begin to diffuse through the water. When the lead ions and iodide ions meet they react to form solid yellow lead iodide which precipitates out of solution.

lead nitrate + potassium iodide → lead iodide + potassium nitrate

Pb(aq) + 2I – (aq) → PbI 2 (s)

The precipitate does not form exactly between the two crystals. This is because the lead ion is heavier and diffuses more slowly through the liquid than the iodide ion.

Another experiment – a teacher demonstration providing an example of a solid–solid reaction  – involves the same reaction but in the solid state.

Additional information

This is a resource from the  Practical Chemistry project , developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany  Practical Physics  and  Practical Biology .

The experiment is also part of the Royal Society of Chemistry’s Continuing Professional Development course:  Chemistry for non-specialists .

© Nuffield Foundation and the Royal Society of Chemistry

• 11-14 years
• 14-16 years
• Practical experiments
• Physical chemistry
• Reactions and synthesis

Specification

• Precipitation is the reaction of two solutions to form an insoluble salt called a precipitate.
• Motion of particles in solids, liquids and gases.
• Diffusion (Graham's law not required).

Related articles

Help learners master equilibrium and reversible reactions

2024-06-24T06:59:00Z By Emma Owens

Use this poster, fact sheet and storyboard activity to ensure your 14–16 students understand dynamic equilibrium

Non-burning paper: investigate the fire triangle and conditions for combustion

2024-06-10T05:00:00Z By Declan Fleming

Use this reworking of the classic non-burning £5 note demonstration to explore combustion with learners aged 11–16 years

Everything you need to introduce alkenes

2024-06-04T08:22:00Z By Dan Beech

Help your 14–16 learners to master the fundamentals of the reactions of alkenes with these ideas and activities

1 Reader's comment

Only registered users can comment on this article., more experiments.

‘Gold’ coins on a microscale | 14–16 years

By Dorothy Warren and Sandrine Bouchelkia

Practical experiment where learners produce ‘gold’ coins by electroplating a copper coin with zinc, includes follow-up worksheet

Practical potions microscale | 11–14 years

By Kirsty Patterson

Observe chemical changes in this microscale experiment with a spooky twist.

Antibacterial properties of the halogens | 14–18 years

By Kristy Turner

Use this practical to investigate how solutions of the halogens inhibit the growth of bacteria and which is most effective

• Contributors
• Email alerts

Site powered by Webvision Cloud

Module 4: Diffusion and Osmosis

Diffusion and osmosis.

The cell membrane plays the dual roles of protecting the living cell by acting as a barrier to the outside world, yet at the same time it must allow the passage of food and waste products into and out of the cell for metabolism to proceed. How does the cell carry out these seemingly paradoxical roles? To understand this process you need to understand the makeup of the cell membrane and an important phenomenon known as diffusion.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration due to random molecular motion. All atoms and molecules possess kinetic energy, which is the energy of movement. It is this kinetic energy that makes each atom or molecule vibrate and move around. (In fact, you can quantify the kinetic energy of the atoms/molecules in a substance by measuring its temperature.) The moving atoms bounce off each other, like bumper cars in a carnival ride. The movement of particles due to this energy is called Brownian motion. As these atoms/molecules bounce off each other, the result is the movement of these particles from an area of high concentration to an area of low concentration. This  is diffusion. The rate of diffusion is influenced by both temperature (how fast the particles move) and size (how big they are).

Part 1: Brownian Motion

In this part of the lab, you will use a microscope to observe Brownian motion in carmine red powder, which is a dye obtained from the pulverized guts of female cochineal beetles.

• Glass slide
• Carmine red powder
• Obtain a microscope slide and place a drop of tap water on it.
• Using a toothpick, carefully add a very minuscule quantity of carmine red powder to the drop of water and add a coverslip.
• Observe under scanning, low, and then high power.

Lab Questions

• Describe the activity of the carmine red particles in water.
• If the slide were warmed up, would the rate of motion of the molecules speed up, slow down, or remain the same? Why?

Part 2: Diffusion across a Semipermeable Membrane

Because of its structure, the cell membrane is a semipermeable membrane. This means that SOME substances can easily diffuse through it, like oxygen, or carbon dioxide. Other substances, like glucose or sodium ions, are unable to pass through the cell membrane unless they are specifically transported via proteins embedded in the membrane itself. Whether or not a substance is able to diffuse through a cell membrane depends on the characteristics of the substance and characteristics of the membrane. In this lab, we will make dialysis tubing “cells” and explore the effect of size  on a molecule’s ability to diffuse through a “cell membrane.”

The following information might be useful in understanding and interpreting your results in this lab:

• Atomic formula: C 20 H 14 O 4
• Atomic mass: 318.32 g/mol
• Color in acidic solution : Clear
• Color in basic solution: Pink
• Atomic formula: I or I2
• Atomic mass: 126 g/mol
• Atomic formula: (C 6 H 10 O 5 )n
• Atomic mass: HUGE!
• Color in Iodine: Bluish
• Atomic formula: NaOH
• Atomic mass: 40.1 g/mol
• Acid/Base: Base
• 2 pieces of dialysis tubing
• Phenolphthalein
• Starch solution
• Using a wax pencil, label one beaker #1. Label the other beaker #2.
• Fill beaker #1 with 300 ml of tap water, then add 10 drops of 1 M NaOH. Do not spill the NaOH—it is very caustic!
• Fill beaker #2 with 300 ml of tap water, then add iodine drops drop by drop until the solution is bright yellow.
• Now prepare your 2 dialysis tubing “bags.” Seal one end of each dialysis tube by carefully folding the end “hotdog style” 2 times, then “hamburger style” 1 time. Tie the folded portion of the tube securely with string. It is critical that your tubing is tightly sealed, to prevent leaks.
• Add 10 ml of water and three drops of phenolphthalein to one of your dialysis tube bags. Seal the other end of the bag by carefully folding and tying as before.
• Thoroughly rinse the bag containing phenolphthalein, then place it in into the beaker containing the NaOH.
• Add 10 ml of starch solution to the other dialysis tube. Again seal the bag tightly and rinse as above. Place this bag containing the starch solution into beaker #2.
• Let diffusion occur between the bags and the solutions in the beakers.

Record the colors (below) and label contents inside and outside the bags (above):

• Which substance diffused across the membrane in beaker #1? How do you know?
• Which substance diffused across the membrane in beaker #2? How do you know?
• Why might some ions and molecules pass through the dialysis bag while others might not?

Part 3: Osmosis and the Cell Membrane

Osmosis is the movement of water across a semipermeable membrane (such as the cell membrane). The tonicity of a solution involves comparing the concentration of a cell’s cytoplasm to the concentration of its environment. Ultimately, the tonicity of a solution can be determined by examining the effect a solution has on a cell within the solution.

By definition, a hypertonic solution is one that causes a cell to shrink. Though it certainly is more complex than this, for our purposes in this class, we can assume that a hypertonic solution is more concentrated  with solutes than the cytoplasm. This will cause water from the cytoplasm to leave the cell, causing the cell to shrink. If a cell shrinks when placed in a solution, then the solution is hypertonic to the cell.

If a solution is hypotonic to a cell, then the cell will swell when placed in the hypotonic solution. In this case, you can imagine that the solution is less concentrated  than the cell’s cytoplasm, causing water from the solution to flow into  the cell. The cell swells!

Finally, an isotonic solution is one that causes no change in the cell. You can imagine that the solution and the cell have equal concentrations, so there is no net movement of water molecules into or out of the cell.

In this exercise, you will observe osmosis by exposing a plant cell to salt water.

What do you think will happen to the cell in this environment? Draw a picture of your hypothesis.

• Elodea leaf
• Microscope slide
• 5% NaCl solution
• Remove a leaf from an Elodea plant using the forceps.
• Make a wet mount of the leaf. Use the pond water to make your wet mount.
• Observe the Elodea cells under the compound microscope at high power (400 X) and draw a typical cell below.
• Next, add several drops of 5% salt solution to the edge of the coverslip to allow the salt to diffuse under the coverslip. Observe what happens to the cells (this may require you to search around along the edges of the leaf). Look for cells that have been visibly altered.

Draw a typical cell in both pond and salt water and label the cell membrane and the cell wall.

• What do you see occurring to the cell membrane when the cell was exposed to salt water? Why does this happen?
• Describe the terms hypertonic, hypotonic and isotonic.
• How would your observations change if NaCl could easily pass through the cell membrane and into the cell?

Part 4: Experimental Design

You and your group will design an experiment to determine the relative molecular weights of methylene blue and potassium permanganate. You may use a petri dish of agar, which is a jello-like medium made from a polysaccharide found in the cell walls of red algae. You will also have access to a cork borer and a small plastic ruler.

• 1 petri dish of agar
• Methlylene blue
• Potassium permanganate

Your experiment design should include all of the following portions:

• Experimental design
• Conclusions
• Further questions/other comments
• Biology Labs. Authored by : Wendy Riggs . Provided by : College of the Redwoods. Located at : http://www.redwoods.edu . License : CC BY: Attribution
• Osmotic pressure on blood cells diagram. Authored by : LadyofHats. Located at : https://commons.wikimedia.org/wiki/File:Osmotic_pressure_on_blood_cells_diagram.svg . License : Public Domain: No Known Copyright

Real Diffusion Experiment (for Home or School)

Introduction: Real Diffusion Experiment (for Home or School)

As part of my research and my physics degrees I've been studying a lot about diffusion and diffusion-related subjects. After a while it finally hit me that I learned about diffusion before - in my highschool biology class. I thought about the experiments they showed us, and something didn't make sense. So I searched YouTube for diffusion demonstrations, and they looked pretty much the same - someone drops a bit of dye into a large water-filled beaker, and after a few minutes the entire beaker is colored.

At this point I realized how big the misconception about diffusion is! Most diffusion demos are completely wrong !

As I'll show you soon enough, diffusion on these scales takes weeks to happen! All of these demos in fact show a process called 'convection' in which the dye mixes due to currents and swirls in the liquid, not due to diffusion.

So, in this instructable I'll first try to convince you that there's something wrong with these experiments, and that we should re-evaluate how we demonstrate diffusion to student. Then, I'll show you how you can perform diffusion experiments the right way (there's more than one way, of course!). Finally, I'll discuss some of the consequences of the results, which can actually teach us a lot about the world we're living in.

My hope is that - if I convince you that the typical diffusion demos are wrong - you spread the word! Teach the ones you can! And on the other hand, if you think that I'm wrong here - I'd love to hear your opinion, see your experimental data, and talk about it!

I've been waiting to make an instructable about this subject for a while now, but I never really got to it. Finally, the science fair contest motivated me getting it done and posting this article :) I hope you like it!

I made a video about this project for those who like watching narrated videos

If you have any questions or comments, I'd love to hear all of them!

Step 1: what's wrong with typical diffusion demos.

In the diffusion demonstrations we're used to seeing, the main things that cause the dye to mix are not diffusion. It is swirls and currents in the liquid, a process called convection. Most commonly, a drop of dye is injected into a large water-filled beaker, and the audience watch as the color mixes (see the GIF I attached of such experiment I performed myself). The spread of the dye is said to be due to diffusion. However, this is not true. You can clearly see currents and swirls in the liquid (convection).

There are many things that cause the convection. First, the beakers are often wide open and so any currents in the air are transferred to the water, causing them to swirl. Next, since the top of the beaker is open, there's evaporation of water happening (see the drawing I attached). This means that the top of the water container becomes cooler than the bottom. Since cold water is slightly denser, it tends to sink, which leads to currents and swirls again. Finally, these experiments are often done with warm water in intent to show that diffusion is temperature-dependent. However, everything I just mentioned is also enhanced with the increased temperature! The difference between the beaker's temperature and the rest of the room is bigger, and so the water develops an even steeper temperature gradient, which makes everything even worse!

Diffusion, as it turns out, can be very very slow. Humans are used to seeing big things - things on the scale of a mm (1/25") are already pretty small for the human eye. However, diffusion is extremely inefficient at these sizes! Diffusion is fast and efficient only on the scale of microns and smaller, and if you follow along, you'll see exactly why!

This should not be discouraging - the fact that diffusion is slow on large scales - but quick on small scales - explains so much of the world around us, including a lot of biological phenomena, and I'll elaborate on that in the final section.

I'm not trying to say that diffusion experiments are impossible to see and demonstrate, I'm just saying that the most common form of diffusion demos is wrong! There are ways to do it right!

Step 2: Experimental Setup

We need to make sure that convection doesn't happen in our experiment. Here are the things that helped me get it done. I tried skipping some of these, but it didn't work :)

• Use a thin container. Glass test tubes or other things with similar proportions could work. These are pretty cheap, I bought mine from AliExpress.
• We should make sure that when we inject the dye, it doesn't swirl right from the start. To do that, I used salt water (5% salt) instead of tap water. This made them heavier and so the dye floated on them. It doesn't change anything for diffusion (why? you can ask your students questions like this one! let me know if you want the answer), but it helps with the initiating the experiment in a controlled manner.
• Let all of the liquids rest at room temperature before starting. If they have different temperatures, it'll cause convection.
• Inject the dye gently to the top of the container so that it floats at the top. Avoid dropping it from a distance.
• Use plastic wrap or a cork cap to seal the test tube after you initiate the experiment. This will help fight the evaporation and air currents from messing with your experiment.
• Finally, this experiment is best done in a constant environment where the temperature is pretty constant over time. If you want to film it, a good place would be inside a cabinet or a closet.

I used a dye called Fluorescein which is very common in laboratories (often used for diffusion experiments). However, food coloring or ink work perfectly fine. If it's water soluble and has a strong color, it should be fine.

Step 3: Data Capture

Capturing the data is important if we want to have a quantitative understanding of the phenomena. It will also let us see the diffusive behavior as a function of time even though things are moving slowly (see the GIF I attached - that's 48 hours!).

• You want the capture data with a nice clear background. I found that using a black paper works well, but it often depends on the type of food coloring or dye you're using.
• You also want to capture images with constant lighting and camera settings. For that reason, I kept the experiment running inside a closet with a fixed light source :) sunrise & sunset can interfere with your data.
• I found a really nice app called 'Open Camera' (thanks Orit !). It allows you to take timelapse images, set the image resolution, and fix the focus / exposure so it doesn't change automatically. You can also save the data to a google drive folder which means you can check how things are going without opening the closet and having the risk of a ruined experiment. You shouldn't take more than an image every 5-10 minutes. Nothing happens that fast anway, the experiment will probably be running for days.
• Before initiating the experiment, take an image with something of a known size. For example, taking a picture of a ruler would be useful. You'll see more about why this is needed in step 6.
• Initiate the experiment and wait. Take the time and follow the images over your google-drive folder. Try to avoid opening the closet while the experiment is running!

Step 4: Data Analysis Software - 'Tracker' (free Academic Software)

There are many ways analyze the experimental data. I found Tracker can be used in so many physics experiments that it's worth getting to know. It's available in many different languages (not only English), so young students from all over the globe can use it.

Download the Tracker software here . There's an online version but it doesn't work well.

An alternative to 'Tracker' is a software called 'ImageJ' or 'Fiji' (basically the same). It works great too, and has some advanced options too.

To start analyzing your videos, import them. Tracker accepts videos of many formats, but also sequences of images. Note that sequences of images need be named in a fixed format with a incrementing numbers. For example, Img001, Img002, Img003... are good file names (see first image)

You'll often want to rotate the image so that the direction you're interested in is horizontal. To do that, right-click the video, and press filters -> new -> rotate. Rotate the image in the desired direction (see second image).

I've also written a code python to analyze a sequence of images automatically , more about that (file included) in the data-analysis step.

Step 5: Calibrate Pixels to Physical Units

We took images or videos of the real world, but the software has no way of knowing what we're looking at, what's it's size, and how often images were taken. We need to calibrate both space (distances) and time to physical units. You'll need to do this even if you analyze the data in a different software.

To Convert Pixels to Distance Units (GIF #1):

• Select the 'calibration tools' from the toolbar.
• Add a new calibration stick.
• Align it along a known distance. For example, I took a picture of a ruler.
• Calibrate the measured distance. I'm using meters, but you can change to any units you like by pressing the 'Coordinate system' tab -> 'Units...' and setting your preferred system of units.

To Calibrate Time (GIF #2):

• Right-click the video (anywhere on the screen), and press 'Clip Settings'
• Set the frame rate (FPS) or the time interval between images in a sequence (dt). I analyzed images that were taken every 30 minutes, so I set 'dt' to 1800 seconds.

You can set the coordinate system (where x, y = 0) and its orientation on the screen by pressing the coordinate axes tool in the toolbar (see third image).

That's it, from this point on your measurements will be in physical units.

Step 6: Measure the Diffusion Process Over Time

I'm including here 3 different types of analysis. I'll list them in order of complexity, the first one being the easiest one to use but also the least accurate, and the last one being the most complex and accurate method of analysis.

First Method - 'By Eye' (GIF #1):

The food coloring (or whatever ink or chemical you're using as dye) colors the water. We can look for the point where it is no longer visible, and track it's position over time.

• In the 'Tracker' software, press 'Track' -> 'New' -> 'Point Mass'.
• Hold 'Shift' and use the mouse choose the point at which the paint is not longer visible. Each time you click, the software will move on to the next frame.
• You can go back and edit points if you like. You can also decide to skip multiple frames in each click by changing the 'step size' at the bottom. This can be useful especially when things change slowly.
• Keep going until you went through all of the video / image sequence.

Second Method - Intensity Profile (GIF #2):

The previous method lacks some accuracy. 'The point where the dye is not longer visible' is not well defined, and depends on the person analyzing the data. A more robust way of analyzing the data is by looking at the intensity profile of the image. Brighter regions have higher intensity than darker regions. We can measure in Tracker as well.

• Add a new Track of a 'Line Profile' type.
• Use Shift to place it along the direction of the diffusion process.
• A window will open on the right side of the screen showing the intensity as a function of distance. Define a point in the intensity profile that you want to track. For example, 'the point where intensity is equal to 50'.
• Measure it's position over time. You'll need to write down the time and position of each point manually (you can write it into an Excel sheet). Students can do this in pairs to save time. I realize this can be time consuming if you go through all of the captured frames, but analyzing about 20-30 frames should be plenty! Adjust the 'step size' so you skip through more than one image at a time.

Third Method (GIF #3):

This method is basically an upgrade of the previous one. I wrote a python code that analyzes the data automatically. It runs through each image and measures the intensity profile along a selected region. It does a few extra things like removing the background noise and such. Also, I used a green dye so it analyzes the green channel of an RGB image, but you can make a small modification to the code to analyze other colors or all of them combined.

• Run the code and analyze your images.
• You'll end up with all of the intensity profiles. All that is left is to track a selected point along the profile. Say, 50 gray points above the background. Define a threshold that would work for your images.
• For each profile, calculate it's distance from the threshold, that is: abs(profile - threshold). The smallest value of this vector will be the point where the profile is equal to the intensity threshold you've chosen, so the easiest way to find it is by looking for: min(abs(profile - threshold). I've attached MATLAB code that does all of this, plots the profiles, and saves them as images.

Attachments

Step 7: how fast are things moving.

Now that we have tracked the diffusion process over time, we can start the final part of the experiment. In this part we will try to answer questions about the rate at which diffusion occurs.

By looking at the images we've aquired we already have an intuitive feeling for it - diffusion starts off pretty fast, but then, as time passes, it slows down. My experiment was running for 48 hours, and the test tube was far from well mixed. The typical distance the dye I used propagated was about 1cm (less than 1/2"). This is very slow, and very typical for diffusion in water!

I made a GIF of the time dependence of the intensity profile for the first 48 hours of the experiment. We can see that the profile changes very rapidly at first, but then it slows down. This is what we see in the images too, so that's a good sign the analysis works :) I then defined the point where the front of the intensity profile reaches a value of 50 gray points above the background intensity, and marked it with an orange circle on each of the profiles (see third method in the previous step for details). I called this point 'x_D' (D for diffusion).

Finally, I plotted x_D as a function of time (see the graph I attached). x_D is shown with orange markers. There's also a blue line on the graph. This graph describes a theoretical fit to the data. Diffusion has a very precise physical formulation which matches reality to very high accuracy. It suggests that diffusion should occur at a rate that scales as the square root of time. In other words, x_D should scale as: x_D ~ sqrt(D * t), where 'D' is the diffusion coefficient of the dye in water and 't' is time. So, I tried to fit the x_D data to a function of the form x_D = sqrt(D * t). The fit is very good, so it seems that diffusion does scale as the square root of time, as expected! I could also use the fitted function to get an estimate for the diffusion coefficient, and found that it is of the order of 4 * 10^-6 [cm^2/sec]. This is very close to the real value of the dye I used (5.5 * 10^-6 [cm^2/sec]). This difference was expected since I could have defined x_D slightly differently and end up with other results. Measuring the exact diffusion coefficient takes a little more effort than what I did here, but for an estimate and order-of-magnitudes this is perfectly fine.

Step 8: Conclusions

We saw that x_D scales as x_D ~ sqrt(D * t). We can now ask, if we wanted for the dye to reach a point x_D away from the source of the dye, how long should we wait? This is answered by inverting the equation: t_D = (x_D ^2)/D. This seems mondane - nothing special, right? But this equaion dictates so much in biology and life. For example, have you ever wondered why cells are small? Why don't we see huge elephant-sized cells? One of the main reasons for that is that cells depend on diffusion to obtain nutrients. If cells were too big, diffusion would become inefficient. Using the diffusion coefficient we found, we see that diffusion will take about 40 minutes to pass just 1mm (1/25.4"), but it would take less than a second to pass a distance of 10 microns , a typical distance to travel when thinking about cells. For instance, when you exercise, your muscle cells need constant supply of oxygen. If the cells were too big (1mm sounds small, right?), diffusion would become inefficient and the oxygen supply wouldn't reach the inside of the cells fast enough. [the sizes-GIF was created base on Learn Genetics ]

To conclude,

We saw that diffusion experiments need careful attention and a lot of patience. I found that the best way to demonstrate this phenomenon is by capturing a video. You can do that with the students if you want to take this into the class-room. Another option would be to initiate the experiment on one day and looking at the results the next day. You'll see the dye has started to mix into the water.

On large scales, diffusion takes a very long time (over a mm or 1/25.4 of an inch is already considered large!), but on very small scales, such as the sizes of cells (a few microns), diffusion is a very efficient way to move things around. This explains a lot about biological processes and other physical phenomena. I think that once you develop intuition for the process and its time-scales, you can appreciate so many things about the world around us.

I hope you found this topic as interesting as I find it! And if you're in the world of teaching, I hope you spread the word! There's a huge misconception about diffusion due to wrongful demonstrations, and it's our job to make things right :)

If you like my instructable and want to see more, you're welcome

To visit my instructables page and my website.

By the way, if you want to support my projects - subscribing to my new YouTube channel is currently the best way to do that! :)

First Prize in the Science Fair Challenge

Recommendations

Make it Resilient

Puzzles and Games Contest

Text Contest

Sciencing_Icons_Science SCIENCE

Sciencing_icons_biology biology, sciencing_icons_cells cells, sciencing_icons_molecular molecular, sciencing_icons_microorganisms microorganisms, sciencing_icons_genetics genetics, sciencing_icons_human body human body, sciencing_icons_ecology ecology, sciencing_icons_chemistry chemistry, sciencing_icons_atomic & molecular structure atomic & molecular structure, sciencing_icons_bonds bonds, sciencing_icons_reactions reactions, sciencing_icons_stoichiometry stoichiometry, sciencing_icons_solutions solutions, sciencing_icons_acids & bases acids & bases, sciencing_icons_thermodynamics thermodynamics, sciencing_icons_organic chemistry organic chemistry, sciencing_icons_physics physics, sciencing_icons_fundamentals-physics fundamentals, sciencing_icons_electronics electronics, sciencing_icons_waves waves, sciencing_icons_energy energy, sciencing_icons_fluid fluid, sciencing_icons_astronomy astronomy, sciencing_icons_geology geology, sciencing_icons_fundamentals-geology fundamentals, sciencing_icons_minerals & rocks minerals & rocks, sciencing_icons_earth scructure earth structure, sciencing_icons_fossils fossils, sciencing_icons_natural disasters natural disasters, sciencing_icons_nature nature, sciencing_icons_ecosystems ecosystems, sciencing_icons_environment environment, sciencing_icons_insects insects, sciencing_icons_plants & mushrooms plants & mushrooms, sciencing_icons_animals animals, sciencing_icons_math math, sciencing_icons_arithmetic arithmetic, sciencing_icons_addition & subtraction addition & subtraction, sciencing_icons_multiplication & division multiplication & division, sciencing_icons_decimals decimals, sciencing_icons_fractions fractions, sciencing_icons_conversions conversions, sciencing_icons_algebra algebra, sciencing_icons_working with units working with units, sciencing_icons_equations & expressions equations & expressions, sciencing_icons_ratios & proportions ratios & proportions, sciencing_icons_inequalities inequalities, sciencing_icons_exponents & logarithms exponents & logarithms, sciencing_icons_factorization factorization, sciencing_icons_functions functions, sciencing_icons_linear equations linear equations, sciencing_icons_graphs graphs, sciencing_icons_quadratics quadratics, sciencing_icons_polynomials polynomials, sciencing_icons_geometry geometry, sciencing_icons_fundamentals-geometry fundamentals, sciencing_icons_cartesian cartesian, sciencing_icons_circles circles, sciencing_icons_solids solids, sciencing_icons_trigonometry trigonometry, sciencing_icons_probability-statistics probability & statistics, sciencing_icons_mean-median-mode mean/median/mode, sciencing_icons_independent-dependent variables independent/dependent variables, sciencing_icons_deviation deviation, sciencing_icons_correlation correlation, sciencing_icons_sampling sampling, sciencing_icons_distributions distributions, sciencing_icons_probability probability, sciencing_icons_calculus calculus, sciencing_icons_differentiation-integration differentiation/integration, sciencing_icons_application application, sciencing_icons_projects projects, sciencing_icons_news news.

• Share Tweet Email Print
• Home ⋅
• Science Fair Project Ideas for Kids, Middle & High School Students ⋅

Simple Experiments for the Relationship Between Diffusion & Temperature

How to Read a Weather Swan Barometer

Diffusion happens when substances move from an area of high concentration to an area of low concentration. When the temperature is higher, it affects the diffusion process because molecules have more energy and move faster. Read on to learn more about diffusion versus temperature with simple experiments.

Experiment 1: Diffusion in a Liquid

For the first simple experiment, you will need a clear container filled with water, food coloring, a darker color such as red is best, and you will need a watch. To start, add a single drop of coloring to the water’s edge in the container and start timing the moment the drop hits the water. Stop timing as soon as the color first reaches the opposite edge of the container. Repeat the procedure after cooling the water in the freezer or heating it up in the microwave or on the stove and compare the results.

Considerations

Make sure that the water stays calm throughout the experiment. For additional variability, you could also use clear liquids other than water, such as vinegar. Use caution when testing other liquids as they may be hazardous, especially when heated or cooled.

Expected Results

At higher temperatures, the water molecules in the container are moving more rapidly, which should cause the food coloring molecules to move more rapidly from one end of the container to the other. The opposite is true when the water is cold.

Experiment 2: Diffusion in a Gas

For the second experiment, you will need a strong-smelling substance and a room connected to an air conditioning system, along with a watch and a second person. Have the other person stand on the opposite side of the room from you and expose the scent to the air. For example, light a candle or spray some air freshener. At the same moment, start timing. When you first detect the scent, stop timing. Next, cool the room down or heat it up using the AC system and repeat the experiment, then compare the results.

Try to remove all sources of air flow from the room. Close all windows and turn off all fans, including the AC fan. Exact times will differ between individuals because each person’s nervous system reacts to smells at different concentrations. Therefore, exact results will not be the same when performed by a second person.

For the purposes of this experiment, the only real difference between a gas and a liquid is how far apart the molecules are, so the results for the second experiment should be similar to the first. At a higher room temperature, the smell should travel faster than at lower room temperatures.

Related Articles

Thermal energy science experiments for kids, how to make water vapor come out of your mouth, how to measure carbonation in soft drinks for a science..., at-home science: color mixing experiment, convection experiments for kids, what happens when you mix pool chlorine & break fluid, what happens when you add a drop of food coloring to..., science projects: how hot & cold water changes a balloon, how to make a hydraulic lift for a school project, how to make a hurricane for a science project, three characteristics of the perfect flame on a bunsen..., science projects using dawn dishwashing liquid, science projects about transfer of energy, water bottle science experiments, how does the body regulate heart rate, how to make an electrical circuit with paper clips, does barometric pressure rise or fall when it rains, how-to science experiments for kids with iodine and..., how to convert cubic feet per second to gallons per....

• What is diffusion?

About the Author

Robert Mullis is is a graduate of Liberty University with a bachelor's degree in biochemistry and a second degree in accounting. As a writer, he specialized in math, biology, chemistry, literature, and business.

Find Your Next Great Science Fair Project! GO

Practical: Investigating Diffusion & Osmosis ( Edexcel IGCSE Biology )

Revision note.

Biology Lead

Practical: Factors that Influence Diffusion

• Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration
• Temperature
• Surface area
• Concentration gradient
• Diffusion distance
• Beetroot cells contain a dark purple-red pigment
• Heating above 45℃ can damage the cell membrane meaning that the pigment can leak out
• The speed at which this pigment leaks out of the cell tells us about the rate of diffusion

Investigating the effect of temperature on diffusion

• Cork borer (optional)
• Cutting board
• Water baths
• The pieces must have the same dimensions so that they all have equal surface areas and volumes , as these factors could affect the rate at which the pigment leaks out
• A cork borer can also be used, as long as the cores are cut to the same length
• To remove any pigment released during cutting
• Put 5 cm 3 of water into 2 test tubes labelled A and B
• Keep test tube A at room temperature and transfer test tube B to a hot water bath at 90℃
• Leave the test tubes for 2 minutes, then add a piece of beetroot into each test tube
• After 10 minutes, observe the colour of the liquid in both test tubes

Results and Analysis

• You should notice that at the higher temperature , more of the pigment has leaked out of the beetroot
• The cell membrane of the beetroot cells has become damaged so more pigment can leak out
• At higher temperatures, particles have more kinetic energy , this results in the faster movement of particles compared to when they have less energy

Investigating the effect of temperature on diffusion in beetroot

Limitations

• Solution: cut the beetroot as accurately as possible using a knife and ruler , and repeat each investigation several times to find a mean
• Solution: conduct several repeats , using different parts of the beetroot and find a mean
• Solution: Set up 5 test tubes in water baths at different temperatures (e.g. 10℃, 20℃, 30℃, 40℃, 50℃)
• Solution: use a colorimeter to measure how much light is absorbed as it passes through each of the five samples of coloured liquid

Applying CORMS to practical work

• When working with practical investigations, remember to consider your CORMS evaluation

CORMS evaluation

• C - We are changing the temperature of the environment
• O - The beetroot cubes will all be taken from the same beetroot or beetroot of the same age
• R - We will repeat the investigation several times to ensure our results are reliable
• M1 - We will observe the colour change of the liquid
• M2 - ...after 10 minutes
• S - We will control the volume of water used, the dimensions of the beetroot cubes and each cube must be blotted before it is weighed each time

Practical: Factors that Influence Osmosis

• Osmosis is the diffusion of water molecules from a dilute solution (high concentration of water) to a more concentrated solution (low concentration of water) across a partially permeable membrane

Osmosis in cells

• We can investigate osmosis using cylinders of potato and placing them into distilled water and sucrose solutions of increasing concentration
• Sucrose solutions (from 0 Mol/dm 3 to 1 mol/dm 3 )
• Paper towels
• Test tube rack
• Prepare a range of sucrose (sugar) solutions ranging from 0 Mol/dm 3 (distilled water) to 1 mol/dm 3
• Set up 6 labelled test tubes with 10cm 3  of each of the sucrose solutions
• Using the knife, cork borer and ruler, cut 6 equally-sized cylinders of potato
• Blot each one with a paper towel and weigh on the balance
• Put 1 piece into each concentration of sucrose solution
• After 4 hours, remove them, blot with paper towels and reweigh them

Experimental method for investigating osmosis in potato cylinders

Results and analysis

• The percentage change in mass can be calculated for each piece of potato

Calculating percentage change in mass

• The potato cylinder in the distilled water will have increased its mass the most as there is a greater concentration gradient in this tube between the distilled water (high water potential) and the potato cells (lower water potential)
• This means more water molecules will move into the potato cells by osmosis , pushing the cell membrane against the cell wall and so increasing the turgor pressure in the cells which makes them turgid - the potato cylinders will feel hard
• The potato cylinder in the strongest sucrose concentration will have decreased its mass the most as there is a greater concentration gradient in this tube between the potato cells (higher water potential) and the sucrose solution (lower water potential)
• This means more water molecules will move out of the potato cells by osmosis , making them flaccid and decreasing the mass of the cylinder - the potato cylinders will feel floppy
• If looked at underneath the microscope, cells from this potato cylinder might be plasmolysed , meaning the cell membrane has pulled away from the cell wall

Plasmolysed red onion cells

• If there is a potato cylinder that has not increased or decreased in mass, it means there was no overall net movement of water into or out of the potato cells
• This is because the solution that the cylinder was in was the same concentration as the solution found in the cytoplasm of the potato cells, so there was no concentration gradient
• Solution: for each sucrose concentration, repeat the investigation with several potato cylinders. Making a series of repeat experiments means that any anomalous results can be identified and ignored when a mean is calculated

Applying CORMS evaluation to practical work

• C - We are changing the concentration of sucrose solution
• O - The potato cylinders will all be taken from the same potato or potatoes of the same age
• M1 - We will measure the change in mass of the potato cylinders
• M2 - ...after 4 hours
• S - We will control the volume of sucrose solution used, the dimensions of the potato cylinders and each cylinder must be blotted before it is weighed each time

Questions involving osmosis experiments are common and you should be able to use your knowledge of these processes to explain the results .Don’t worry if it is an experiment you haven’t done – simply figure out where the higher concentration of water molecules is – this is the solution with the higher water potential - and explain which way the molecules move due to the differences in water potential .

You've read 0 of your 0 free revision notes

Get unlimited access.

to absolutely everything:

• Downloadable PDFs
• Unlimited Revision Notes
• Topic Questions
• Past Papers
• Model Answers
• Videos (Maths and Science)

Join the 100,000 + Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

Examples of Diffusion in Chemistry

10 Diffusion Examples

Science Photo Library Ltd/Getty Images

• Chemical Laws
• Periodic Table
• Projects & Experiments
• Scientific Method
• Biochemistry
• Physical Chemistry
• Medical Chemistry
• Chemistry In Everyday Life
• Famous Chemists
• Activities for Kids
• Abbreviations & Acronyms
• Weather & Climate
• Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
• B.A., Physics and Mathematics, Hastings College

Diffusion is the movement of atoms, ions, or molecules from an area of higher concentration to one of lower concentration. The transport of matter continues until equilibrium is reached and there is a uniform concentration through the material.

Examples of Diffusion

• Diffusion is the movement of particles from higher concentration to lower concentration.
• Diffusion continues until equilibrium is reached. At equilibrium, concentration is the same throughout the sample.
• Familiar examples of diffusion are the transport of perfume when it is sprayed in a room or the movement of food coloring in a glass of water.
• Perfume is sprayed in one part of a room, yet soon it diffuses so that you can smell it everywhere.
• A drop of food coloring diffuses throughout the water in a glass so that, eventually, the entire glass will be colored.
• When steeping a cup of tea, molecules from the tea cross from the tea bag and diffuse throughout the cup of water.
• When shaking salt into water, the salt dissolves and the ions move until they are evenly distributed.
• After lighting a cigarette, the smoke spreads to all parts of a room.
• After placing a drop of food coloring onto a square of gelatin, the color will spread to a lighter color throughout the block.
• Carbon dioxide bubbles diffuse from an open soda, leaving it flat.
• If you place a wilted celery stick in water, water will diffuse into the plant, making it firm again.
• Water diffuses into cooking noodles, making them bigger and softer.
• A helium balloon deflates a little bit every day as helium diffuses through the balloon into the air.
• If you place a sugar cube in water, the sugar will dissolve and evenly sweeten the water without having to stir it.

Simple Diffusion Experiment

See diffusion for yourself with this simple experiment.

• 2 water glasses
• Baby oil or vegetable oil
• Food coloring
• Fill a glass mostly full of water.
• In a second glass, add a bit of oil and some drops of food coloring. You can use multiple colors of food coloring, but take care to avoid mixing them.
• Stir together the oil and food coloring so that you break the drops into smaller ones.
• Pour the oil and food coloring into the water glass. The food coloring drops into the water and diffuses into it.

Expand upon this project by comparing the rate of diffusion in hot water versus cold water. If you use different colors of food coloring, explore color theory and see what you get when two different colors mix. For example, red and blue make purple, yellow and blue make green, and so on. Can you explain why food coloring diffuses in the water, but no into the oil?

Diffusion vs Other Transport Processes

Diffusion, together with osmosis and facilitated diffusion, are types of passive transport processes. What this means is that energy is not required for these processes to occur. They are thermodynamically favorable and driven by chemical potential or Gibbs free energy.

In contrast, active transport processes require the input of energy to occur. Active transport includes primary (direct) active transport and secondary (indirect) active transport. The first uses energy molecules as transport mediators. The second couples molecule movement with a thermodynamically favorable transport.

Types of Diffusion

There are several types of diffusion, including:

• Anisotropic diffusion enhances high gradients.
• Atomic diffusion occurs in solids.
• Bohm diffusion involves plasma transport across magnetic fields.
• Eddy diffusion involves turbulent flow.
• Knudsen diffusion is diffusion of a gas through long pores where wall collisions occur.
• Molecular diffusion is movement of molecules from high concentration to low concentration.
• Barr, L.W. (1997). "Diffusion in Materials". DIMAT 96 . Scitec Publications. 1: 1-9.
• Bromberg, S.; Dill, K.A. (2002). Molecular Driving Forces: Statistical Thermodynamics in Chemistry and Biology . Garland Science. ISBN 0815320515.
• Kirkwood, J.G.; Baldwin, R.L.; et al. (1960). "Flow equations and frames of reference for isothermal diffusion in liquids". The Journal of Chemical Physics . 33(5): 1505–13.
• Muir, D. C. F. (1966). "Bulk flow and diffusion in the airways of the lung". British Journal of Diseases of the Chest . 60 (4): 169–176. doi:10.1016/S0007-0971(66)80044-X.
• Stauffer, Philip H.; Vrugt, Jasper A.; Turin, H. Jake; Gable, Carl W.; Soll, Wendy E. (2009). "Untangling Diffusion from Advection in Unsaturated Porous Media: Experimental Data, Modeling, and Parameter Uncertainty". Vadose Zone Journal . 8 (2): 510. doi:10.2136/vzj2008.0055
• A to Z Chemistry Dictionary
• What Is Diffusion in Chemistry?
• Differences Between Osmosis and Diffusion
• Examples of Chemical Reactions in Everyday Life
• How Reverse Osmosis Works
• Learn About Diffusion
• Defining Active and Passive Transport
• Water Fireworks for Kids
• Osmosis Definition in Chemistry
• Osmotic Pressure and Tonicity
• Diffusion: Passive Transport and Facilitated Diffusion
• Kindergarten Science Projects
• What Is the Zeroth Law of Thermodynamics?
• How To Make a Rainbow in a Glass
• Trading Places: Liquid Science Magic Trick
• Kid-Friendly Elephant Toothpaste Demo

The Kitchen Pantry Scientist

Simple recipes for real science, diffusion and osmosis experiments.

Think about the way pollutants move from one place to another through air, water and even soil. Or consider how bacteria are able to take up the substances they need to thrive. Your body has to transfer oxygen, carbon dioxide and water by processes involving diffusion as well.

Lots of things can affect how fast molecules diffuse, including temperature.  When molecules are heated up, they vibrate faster and move around faster, which helps them achieve equilibrium more quickly than they would if it were cold.

Diffusion takes place in gases (like air), liquids (like food coloring moving through water,) and even solids (semiconductors for computers are made by diffusing elements into one another.)

Every so often, measure the circle of food coloring as it diffuses into the jello around it.  How many cm per hour is it diffusing?  If you put one plate in the refrigerator and an identical one at room temperature, do they diffuse at the same rate?  Why do you think you see more than one color for certain shades of food coloring? What else could you try?

Here’s a post on how to use this experiment to make sticky window decorations:   https://kitchenpantryscientist.com/?p=4489

We made plates and did the same experiment using 2 cups of red cabbage juice , 2 cups of water and 4 packs of gelatin to see how fast a few drops of vinegar or baking soda solution would diffuse (a pigment in red cabbage turns pink when exposed to acid, and blue/green when exposed to a base!)

It’s also fun to experiment with the diffusion of substances across a membrane, like a paper towel.  This is called osmosis. Membranes like the ones around your cells are selectively permeable and let water and oxygen in and out, but keep other, larger molecules from freely entering and exiting your cells.

For this experiment, you’ll need a jar (or two), paper towels, rubber bands and food coloring.  Fill a jar with water and secure a paper towel in the jar’s mouth (with a rubber band) so that it hangs down into the water, making a water-filled chamber that you can add food coloring to.  Put a few drops of food coloring into the chamber and see what happens.

top “chambers” for food coloring

Are the food coloring molecules small enough to pass through the paper towel “membrane?”  What happens if you put something bigger, like popcorn kernels in the chamber? Can they pass through the small pores in the paper towel?

Do the same experiment in side-by-side jars, but fill one with ice water and the other with hot  water.  Does this affect the rate of osmosis or how fast the food coloring molecules diffuse throughout the water?

Think about helium balloons.  If you take identical balloons and fill one with helium and the other with air, the helium balloon will shrink much faster as the smaller helium atoms diffuse out more quickly than the larger oxygen molecules.

Tags: diffusion , experiment , kids , osmosis In: Biology Experiments , Chemistry Experiments , Physics Experiments | 8 comments »

Leave a comment

Name (required)

Mail (will not be published) (required)

XHTML: You can use these tags: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

• Skip to primary navigation
• Skip to main content
• Skip to primary sidebar

• FREE Experiments
• Kitchen Science
• Climate Change
• Egg Experiments
• Fairy Tale Science
• Edible Science
• Human Health
• Inspirational Women
• Forces and Motion
• Science Fair Projects
• STEM Challenges
• Science Sparks Books
• Contact Science Sparks
• Science Resources for Home and School

Tea bag diffusion!

January 2, 2012 By Emma Vanstone 9 Comments

I love a good cup of tea. In fact, I cannot actually function without one first thing in the morning. If you’re like me, then this investigation is definitely needed in your house so that you can ensure your kids are equipped with the best tea-making skills and have the best scientific knowledge to back up what makes a good cup of tea! This investigation looks at diffusion through the partially permeable membrane of a tea bag.

So firstly, we want to know what type of teabag makes the best drink?

Is it a square, a pyramid or a circle bag?

The activity involves using hot water, so adult supervision is essential.

Teabag diffusion

You’ll need

A stopwatch/timer

A piece of white paper

3 clear glass mugs (you are going to add hot water, so not thin ones that could crack)

Circle, triangle and pyramid tea bags

Thermometer or kettle

1. On the piece of white paper, draw a cross with a marker pen

2. Place one mug over the cross

3. Add the circle teabag

4. Boil water from the kettle and measure out 150ml (if you have a thermometer, you can improve reliability by keeping the temperature constant)

5. Pour over the teabag and start the stopwatch

6. Time how long it takes for the cross to disappear

7. Repeat with the pyramid and square teabag.

8. To make the investigation results more accurate, repeat with each teabag three times.

Record your results in a table

How does the tea diffuse into the water?

So which teabag was quicker?

You should find that the pyramid teabag was the quickest.

Why do you think this is?

As the water is added to the teabag, it causes the tea leaves to move and triggers diffusion of the leaves. Diffusion is defined as the movement of a substance from an area of higher concentration to an area of lower concentration. There are lots of tea molecules in the bag and none outside. The leaves themselves can’t pass through the bag, but their smaller particles containing colour and flavour can (the teabag itself acts as the partially permeable membrane). The addition of heat (from the hot water) to the tea bag causes its molecules to move much faster than at room temperature. This energy is more readily released in a shorter period of time than a tea bag filled with room temperature or cold water. The teabag shape affects the surface area and the pyramid due to its 3D shape providing more surface area for diffusion to take place and more area in the middle for the tea molecules to move around in spreading the colour and flavour.

Ok, so now they know which is the best teabag to use and how to let it brew…so I suggest you ask for a nice cuppa now!

Last Updated on February 23, 2023 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

January 06, 2012 at 8:20 pm

What a fun experiment. You always find ways to make the most ordinary things interesting. Thanks for sharing on Monday Madness.

January 06, 2012 at 9:43 pm

January 08, 2012 at 5:37 pm

Interesting especially since all my tea bags are rectangular. I don’t drink it a lot, but and getting to like it more and more. I haven’t tried many brands yet so I will have to start exploring it more. Fun exploration with the kids and I think they probably learned a lot about figuring things out on their own from it.

October 23, 2013 at 2:29 am

awesome job

February 17, 2014 at 8:32 pm

Jah hey thnx.i have learned smthng http://

February 23, 2014 at 12:40 am

Where did the square teabags come from? I have enjoyed tea in that shape but can’t recall what brand. Thanks!

April 29, 2014 at 7:13 pm

thanks! thats really helpful we’re doing a science project on how the shape of the tea bag affects the taste so that was really helpful!!

September 17, 2017 at 11:32 pm

Interesting and helpful. Thanks a lot. Although the cross takes a long time to remove for some reason. Wasnt sure in what marker to use though.

September 29, 2019 at 5:28 pm

WOW i love talking about tea irs so fun wowowowow i learnt science from tea omg wowowowowow omg tea is so interesting

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

DIY: Diffusion Science Experiment

September 7

Related Posts

How does a speaker work, center of mass fork experiment, can you make dry ice cream.

Leveraging Crosslinker Diffusion to Template Stiffness Gradients in Alginate Hydrogels

• Find this author on Google Scholar
• Find this author on PubMed
• Search for this author on this site
• ORCID record for Ian C Schneider
• For correspondence: [email protected]
• Info/History
• Preview PDF

Mechanobiology or the response of cells to forces or mechanical properties of their environment drives many physiological and pathological processes including development, wound healing, fibrosis and cancer. A variety of cell biological behaviors are driven by local mechanical properties including stem cell differentiation and drug resistance. Furthermore, cells can sense stiffness gradients and migrate up the gradient in a process called durotaxis. The development of 3D hydrogel systems with tunable mechanical gradient patterns affords the ability to run multiple experiments at different stiffness. This is critical as some cell behavior is not monotonically dependent upon stiffness. Additionally, the creation of mechanical property gradients within 3D hydrogels may be able to guide cells to particular targets forming complex cellular structures within the hydrogel or enhancing wound healing through directed migration. In this paper, we developed an approach to spatially imprint within alginate hydrogels, gradients in mechanical properties that can be used to probe mechanobiology. Stencils were easily designed and fabricated using a common craft cutter to control the presentation of a calcium crosslinking solution to alginate gels. Different stencil shapes result in different gradients in opacity that can be imprinted into both thick and thin alginate gels of arbitrary shape. The steepness of the opacity gradient as well as the maximum opacity can be controlled based on reproducible crosslinking kinetics regulated through calcium concentration and gradient developing time. Calcium crosslinking results in both opacity changes as well as increases in elastic modulus in the bulk hydrogel. Opacity correlates with elastic modulus, allowing it to be used as a proxy for local elastic modulus. Consequently, spatial gradients in elastic modulus can also be imprinted into alginate gels using this stenciling approach. This stenciling approach represents a facile way to control stiffness gradients in alginate gels.

Competing Interest Statement

The authors have declared no competing interest.

View the discussion thread.

Thank you for your interest in spreading the word about bioRxiv.

NOTE: Your email address is requested solely to identify you as the sender of this article.

Citation Manager Formats

• EndNote (tagged)
• EndNote 8 (xml)
• RefWorks Tagged
• Ref Manager
• Tweet Widget
• Facebook Like
• Google Plus One

Subject Area

• Bioengineering
• Animal Behavior and Cognition (5417)
• Biochemistry (12221)
• Bioengineering (9149)
• Bioinformatics (30189)
• Biophysics (15492)
• Cancer Biology (12603)
• Cell Biology (18085)
• Clinical Trials (138)
• Developmental Biology (9760)
• Ecology (14631)
• Epidemiology (2067)
• Evolutionary Biology (18787)
• Genetics (12557)
• Genomics (17236)
• Immunology (12325)
• Microbiology (29062)
• Molecular Biology (12068)
• Neuroscience (63286)
• Paleontology (464)
• Pathology (1939)
• Pharmacology and Toxicology (3373)
• Physiology (5194)
• Plant Biology (10817)
• Scientific Communication and Education (1710)
• Synthetic Biology (3007)
• Systems Biology (7547)
• Zoology (1692)

• {{subColumn.name}}

AIMS Mathematics

• {{newsColumn.name}}
• Share facebook twitter google linkedin

Stability analysis of a class of nonlinear magnetic diffusion equations and its fully implicit scheme

• Gao Chang 1,2 , 
• Chunsheng Feng 1 , 
• Jianmeng He 1 , 
• Shi Shu 1 ,  , 
• 1. School of Mathematics and Computational Science, Xiangtan University, Xiangtan, Hunan, 411105, China
• 2. College of General Education, Shanxi Institute of Science and Technology, Jincheng, Shanxi, 048000, China
• Received: 06 May 2024 Revised: 06 June 2024 Accepted: 13 June 2024 Published: 27 June 2024

MSC : 35L03, 35L65, 65M08

• Full Text(HTML)
• Download PDF
• nonlinear magnetic diffusion equation ,
• step-function resistivity ,
• stability ,
• implicit finite volume method

Citation: Gao Chang, Chunsheng Feng, Jianmeng He, Shi Shu. Stability analysis of a class of nonlinear magnetic diffusion equations and its fully implicit scheme[J]. AIMS Mathematics, 2024, 9(8): 20843-20864. doi: 10.3934/math.20241014

Related Papers:

• This work is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 4.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/ -->

Supplements

Access History

• Corresponding author: Email: [email protected]

Reader Comments

• © 2024 the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0 )

通讯作者: 陈斌, [email protected]

沈阳化工大学材料科学与工程学院 沈阳 110142

Article views( 52 ) PDF downloads( 13 ) Cited by( 0 )

Figures and Tables

Figures( 6 )  /  Tables( 10 )

Associated material

Other articles by authors.

• Chunsheng Feng
• Jianmeng He

Related pages

• on Google Scholar
• Email to a friend
• Order reprints

Export File

• Figure 1. Comparison between step-function and smoothed step-function resistivity
• Figure 2. Magnetic field and internal energy density with step-function resistivity
• Figure 3. Magnetic field and internal energy density with smoothed step-function resistivity
• Figure 4. Comparison of different space steps
• Figure 5. Comparison of different time steps
• Figure 6. Comparison of magnetic field and internal energy density

Q-DiT: Accurate Post-Training Quantization for Diffusion Transformers

• Jiang, Jingyan

Recent advancements in diffusion models, particularly the trend of architectural transformation from UNet-based Diffusion to Diffusion Transformer (DiT), have significantly improved the quality and scalability of image synthesis. Despite the incredible generative quality, the large computational requirements of these large-scale models significantly hinder the deployments in real-world scenarios. Post-training Quantization (PTQ) offers a promising solution by compressing model sizes and speeding up inference for the pretrained models while eliminating model retraining. However, we have observed the existing PTQ frameworks exclusively designed for both ViT and conventional Diffusion models fall into biased quantization and result in remarkable performance degradation. In this paper, we find that the DiTs typically exhibit considerable variance in terms of both weight and activation, which easily runs out of the limited numerical representations. To address this issue, we devise Q-DiT, which seamlessly integrates three techniques: fine-grained quantization to manage substantial variance across input channels of weights and activations, an automatic search strategy to optimize the quantization granularity and mitigate redundancies, and dynamic activation quantization to capture the activation changes across timesteps. Extensive experiments on the ImageNet dataset demonstrate the effectiveness of the proposed Q-DiT. Specifically, when quantizing DiT-XL/2 to W8A8 on ImageNet 256x256, Q-DiT achieves a remarkable reduction in FID by 1.26 compared to the baseline. Under a W4A8 setting, it maintains high fidelity in image generation, showcasing only a marginal increase in FID and setting a new benchmark for efficient, high-quality quantization in diffusion transformers. Code is available at \href{https://github.com/Juanerx/Q-DiT}{https://github.com/Juanerx/Q-DiT}.

• Computer Science - Computer Vision and Pattern Recognition;
• Computer Science - Artificial Intelligence

Help | Advanced Search

Computer Science > Computer Vision and Pattern Recognition

Title: udhf2-net: an uncertainty-diffusion-model-based high-frequency transformer network for high-accuracy interpretation of remotely sensed imagery.

Abstract: Remotely sensed image high-accuracy interpretation (RSIHI), including tasks such as semantic segmentation and change detection, faces the three major problems: (1) complementarity problem of spatially stationary-and-non-stationary frequency; (2) edge uncertainty problem caused by down-sampling in the encoder step and intrinsic edge noises; and (3) false detection problem caused by imagery registration error in change detection. To solve the aforementioned problems, an uncertainty-diffusion-model-based high-Frequency TransFormer network (UDHF2-Net) is the proposed for RSIHI, the superiority of which is as following: (1) a spatially-stationary-and-non-stationary high-frequency connection paradigm (SHCP) is proposed to enhance the interaction of spatially stationary and non-stationary frequency features to yield high-fidelity edge extraction result. Inspired by HRFormer, SHCP remains the high-frequency stream through the whole encoder-decoder process with parallel high-to-low frequency streams and reduces the edge loss by a downsampling operation; (2) a mask-and-geo-knowledge-based uncertainty diffusion module (MUDM) is proposed to improve the robustness and edge noise resistance. MUDM could further optimize the uncertain region to improve edge extraction result by gradually removing the multiple geo-knowledge-based noises; (3) a semi-pseudo-Siamese UDHF2-Net for change detection task is proposed to reduce the pseudo change by registration error. It adopts semi-pseudo-Siamese architecture to extract above complemental frequency features for adaptively reducing registration differencing, and MUDM to recover the uncertain region by gradually reducing the registration error besides above edge noises. Comprehensive experiments were performed to demonstrate the superiority of UDHF2-Net. Especially ablation experiments indicate the effectiveness of UDHF2-Net.

Submission history

Access paper:.

• Other Formats

References & Citations

• Google Scholar
• Semantic Scholar

BibTeX formatted citation

Bibliographic and Citation Tools

Code, data and media associated with this article, recommenders and search tools.

• Institution

arXivLabs: experimental projects with community collaborators

arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website.

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs .