salinity and density experiment

Sink or Float: Density of Salt Water

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Today I want to show you a Sink or Float Salt Water Density activity we did.  I have been wanting to do this activity for a long time and I’m glad we finally got around to it!

We experimented with the salinity of water and how it affects items sinking or floating.  We did this on the density of water based on its salt content by using fresh water, and also water with the approximate salt content in the ocean, the Great Salt Lake, the Dead Sea (bordering Israel and Jordan).

I have spent a lot of time around different bodies of salt water in my life. I grew up in Florida right by the ocean and spent many many days swimming in the ocean there.

I also had the opportunity to do a semester abroad in Israel and swam in the Dead Sea while there.

Now, I live near the Great Salt Lake and have had the opportunity to visit it with my children.  The last time we visited the Salt Lake as a family, I started thinking about trying this sink or float experiment at home with my kids.

I remember swimming in the Dead Sea. The amount of salt in the water makes your skin sting a bit when you go in.  It is nearly impossible to not float due to the high density of the water. It is a strange feeling to just float so easily in water with very little effort.  There is a similar feeling in the Salt Lake.

Different amounts of salt in the water will create different densities. Denser water will create greater buoyancy, meaning things will float more. We decided to simulate this by trying to recreate water with the same amount of salt as each of these bodies of water.

Since we had some background knowledge to this already, we knew our predictions would likely be correct. The more salt you add to water, the more dense it will be, and thus the more likely it will be that items will float in it.

How to Do the Sink or Float: Density of Salt Water Experiment

Supplies We Used:

Quart sized glass jars, wide mouth

Measuring cup and teaspoon

Various household objects

In deciding how much salt we put into the water, we based it on the percentage of salt in each body of water. I used a food scale to measure it in grams. This makes it a little easier anymore accurate.

Our control was the fresh tap water. We filled one jar with 3 cups or 720 g. of regular water and tested what would float in it. We used a few different items to compare. We put the same amount of water in each jar with varying amounts of salt percentages.

Quantity of Salt in Ocean Water:

The next jar was our ocean water. Salty ocean water is 3.5% salt. So in a jar with 3 cups or 720 g. of water that would equal 25.2 grams of salt. A teaspoon was approximately 6.5 g. of salt or 3 3/4 tsp. salt.

Quantity of Salt in the Great Salt Lake

For our third jar of water, we created water similar to the salinity of the water in the Great Salt Lake. This one is tricky because the salt levels fluctuate based on the water levels of the lake and also the location in the lake. Some areas have a higher salt content than others. I decided to go with sort of a middle, average range of 15%. That equaled 108 grams of salt which is a little more than 1/3 c of salt in 3 c. of water.

Quantity of Salt in the Dead Sea

The fourth jar of water represented the Dead Sea. The water in the Dead Sea is one of the saltiest bodies of water on the earth’s surface.  There is eight times more salt in Dead sea than ocean 36% salt!  At 36% salt that equals 259.2 grams of salt (about 3/4 c.) of salt in the 720 g. (3 c.) of water.

Saltiest Body of Water: Gaet’ale Pond

The Dead Sea is not the saltiest body of water on earth. Gaet’ale Pond in Ethiopia is 43% salt, but you can’t swim in this one!  It’s typically over 120 degrees Fahrenheit and emits toxic gases.  We did not test out the density of this one, but it is a fun fact to teach!

Will it Sink or Float?

Once the jars have both the salt and water, stir them with a spoon until the salt is dissolved as much as possible. It may get a little messy, so if you are concerned about mess, do this experiment outside, over a sink or in a small tub to catch the spills.

Now you can test out the density of each of the jars of water by seeing what things will sink or float in each jar.

Objects to Try for the Sink or Float Experiment

We tested out each of the jars of water with several common household items.  You can try anything, but here are some ideas:

• wooden blocks
• hard-boiled egg vs. a raw egg
• cherry tomatoes
• plums, apples, oranges, grapes
• highlighter pens (pencils and crayons would work well)
• ping pong balls or bouncy balls, aluminum foil rolled into a tight ball
• small toys- like lego, or army men, small toy cars
• small objects like a coin, a paper clip, dry pasta, eraser, bottle cap, buttons, coins

Try a variety of dense objects and buoyant objects so you can get a better idea of how they work.

It was really fun to make a prediction of each object and then see which guesses were correct. Sometimes we were surprised by the outcome. It was also surprising to see how much more things would float in the the saltiest water.

Our predictions that overall liquids with more salt will have a higher density and fresh water will have a low density.

Sometimes an object would sink in the fresh water, but float in all of the salt water jars, no matter the amount of salt. Sometimes we could see that the object would sit higher or lower at the top of the water.

We really enjoyed this experiment and hope you will, too!

See More Water Experiments: 25 Water Science Experiments and Activities!

Also check out this  Density Experiment for Kids where we tested the density with different liquids and substances including corn syrup, gel, and more!

Former school teacher turned homeschool mom of 4 kids. Loves creating awesome hands-on creative learning ideas to make learning engaging and memorable for all kids!

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Water salinity and density.

In this experiment, discover how the density of salt water can create interesting effects in nature.

Evan is back with another impressive water experiment that you can try at home to learn about water salinity and density.

Fresh water is less dense than salt water, so it can sit on top. In undistributed waters, they can remain as separate bodies for a long time! This is referred to as a  salt wedge.  Did you know there is a pretty amazing salt wedge in the swan river? The wedge of salt water can move up to 55km upstream of the Swan River.

What you’ll need:

• 2 plastic trays
• A plastic clipboard (or a thin plastic chopping board)
• 5 litres of water
• Measuring spoons
• Mixing spoon
• 2 different colours of food colouring
• 5 jars with a flat rim (big enough to hold about a litre of water each)

Instructions

• Fill each jar with water. Place your egg in the first jar and watch how it sinks to the bottom. This is because the egg is more dense than the water around it.
• In the same jar, start adding large scoops of salt into the water. You may need to stir the salt around to ensure it dissolves into the water. Keep adding salt until the egg floats to the top. When this happens, the water is now more dense than the egg.
• Next, let’s see what happens when fresh water and salt water meet. Grab two more jars of fresh water, and place one of the jars onto one of your plastic trays. Add a few drops of one colour of food colouring to the first jar, then add a different colour to the second jar.
• To the first jar on your plastic tray, add a spoonful of salt and stir. Place the plastic board on top of the second jar, and hold tight to flip the jar over. With the board still in place underneath the second jar, place it on top of the first jar and ensure the openings of both jars are aligned. Carefully remove the board from between the jars.
• Notice how the colours contained within each jar of water don’t mix: this is because the “fresh” water in in the second jar is less dense than the salty water in the first.

In nature, this effect is known as a “halocline”. When a river of freshwater meets the ocean, the fresh water flows on top of the salty water, until forces like wind and waves mix them together.

• Let’s see what happens when we put fresh water on the bottom and salt water on top. Repeat Steps 3-4, this time placing the jar of salt water on top. Notice how the denser, salty water rushes to the bottom of the other jar and the colours mix together.

Looking for more activities to do at home?

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Salt Water Density Experiment

Introduction: Salt Water Density Experiment

Step 1: Materials

Step 2: Procedure

Step 3: Additional Ideas and Resources

Extension/Modification Ideas:

• Use a triple beam balance of electronic scale to teach or practice that skill
• Use hot and cold water instead.
• Compare salt and fresh water and connect with the environment.
• Have older students teach this to younger students.
• Use other liquids to make density columns. (Water, oil, alcohol, etc.)
• Make a much larger one as part of a science night.
• Let students try making different density salt solutions and try to figure out which ones work the best and how that relates to density.

Other Density Demos:

• Egg in salt water or tap water
• Ice in water or rubbing alcohol

Attachment: I attached a Word document that is a template for a guided lab report that you feel free to modify and use. Other Ideas and Resources: These are just some ideas and alternate extensions. Some additional references will many different versions of this same idea: DENSITY: SALTWATER COLUMN LAB TEACHER PREPARATION Explains a different way to prepare solutions and some "discussion" questions as a worksheet for students Liquid Rainbow Written from the standpoint of ocean science for elementary school. Contains a lot of "teacher lingo" (e.g. key concepts, big idea, objectives, etc.) GEMS: Discovering Density book This book costs $18, but I think is where I first saw the idea for this lab. The handouts are free online in Spanish. So that might make this a cool activity to do with students learning Spanish too! Steve Spangler 7-Layer Density Column This link provides a video showing a different density experiment with different types of liquids to see how their relative densities are different. They do use the word "heavier" instead of density. He uses a slightly different way of layering. NOAA Lesson Plan: Hot, Cold, Fresh and Salty Another Earth Science/Oceans connection. This lesson plan gives ideas about having students compare hot and cold water and fresh and salty water. These are extensions that would be great to add to a simpler lesson like the one I posted.

Step 4: Real World Connection

In research labs, human blood is carefully pipetted to form a layer on top of a substance called Ficoll-Paque (made by GE). When this tube is centrifuged, the red blood cells (the most dense) go to the bottom, the Ficoll is (the next most dense), then the white blood cells, and finally the plasma (the least dense). Labs use this technique to isolate different parts of the blood. For instance, if you want to isolate the white blood cells, you can remove the plasma layer (yellow) and then gently extract the thin cloudy white layer that contains the white blood cells. Wikipedia's Ficoll-Paque Article This page describes the basics of Ficoll Ficoll-Paque PLUS Manufacturer's Description A short paragraph from the manufactures that uses the word density multiple times Ficoll-Paque Instructional Video This video shows the layering of blood on top of the Ficoll very slowly and gently and the final layers that form

Step 5: Graphic Organizer Word Document

Someone let me know the Word document does not open currently. I tried uploading another version but it also says forbidden. Message me and I can try to send it to you.

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Salt Water Density Experiment

Can you make a fresh egg float in water? What will happen to an egg in a saturated solution of salt water? Will an egg float or sink in salt water? What is density? What is buoyancy? There are many questions and hypotheses (predictions) to make with this easy salt water experiment, and you can learn about it all with just water, salt, and eggs! Check out all our classic science experiments for more great ideas!

SALT WATER DENSITY EXPERIMENT

Let’s get ready to investigate! Head to the kitchen, open the pantry, and be prepared to get a little salty. And if you are curious about the rubber egg experiment in the video, click here .

YOU WILL NEED:

• 2 Tall glasses big enough to hold an egg

SALT WATER EXPERIMENT SET UP:

STEP 1:  Start by filling one glass about 2/3 of the way full with water. Ask the kids what will happen if you carefully drop an egg into the glass of water. Now go ahead and do it!

STEP 2:  In the other glass, fill to the same height with water. Now stir in 3 tablespoons of salt. Mix well to dissolve the salt! Ask the kids what they think will happen this time and demonstrate!

TIP: Now’s a great time to talk about mixtures. By combining salt and water, you are making a mixture, an important science concept ( Grab a free printable list of science words )!

A mixture is a material made up of two or more substances mixed together. No chemical reaction takes place, and you can separate the substances in the mixture. You can have a mixture of liquids, solids, or gases.

The second egg should float due to the water’s density change!

SALT WATER DENSITY IN THE CLASSROOM

Kids can easily experiment with different objects from around the room. Small plastic items will work best with the measurements of salt and water provided.

If the item still sinks in the salt water, ask the kids what they think! Should they add more salt? Have each kid contribute an item to the experiment!

This is a great experiment to add to your ocean science lesson plans because the ocean is salty!

So many great saltwater density questions:

• Do you float better in salt water?
• What about some of the biggest mammals on earth that float easily in the ocean?
• Does the density of the saltwater play a role?

Why is the ocean salty? The simple answer is that the salt comes from the rocks on the land that has been broken down by erosion and is carries by streams to the ocean.

WHAT IS DENSITY?

Why do some objects sink while another object floats? An object sinks because it is denser or heavier than water and vice versa. Our sink and float experiment is another exciting way to look at items that might surprise you using only water.

Big items that feel light, like a ping pong ball, are less dense than smaller items that feel heavy, like a gold ring. When added to water, objects denser than water sink, and those less dense than water float. Hollow things often float as air is less dense than water. Learn more about what is density.

You can experiment with many objects that sink and float in water, but what happens when you add salt to the water? Can you change whether the object, like the egg, still sinks?

How does salt affect the density of water?

Adding salt to water densifies it. As the salt dissolves in the water, it adds mass (more weight to the water). This densifies the water and allows more objects to float on the surface that would sink in fresh water. This is an example of a physical change !

Do objects float better in saltwater or freshwater?

What other items can you find to test? Most items will generally float in this salt water experiment even if they sink in freshwater. Just look at the egg!

CHECK OUT MORE SIMPLE SCIENCE IDEAS

• Sink the Boat Buoyancy Challenge
• Freezing Point of Water
• Frost on a Can (not just for winter!)
• Sink or Float Experiment
• Do Oranges Sink or Float?
• What Dissolves in Water?

Turn It Into A Science Fair Project

Science projects are an excellent way for older kids to show what they know about science. They can also be used in all sorts of environments, including classrooms and groups.

Kids can take everything they have learned about using the scientific method , stating a hypothesis, choosing variables , making observations , and analyzing and presenting data.

Want to turn one of these experiments into an awesome science fair project? Check out these helpful resources.

• Science Project Tips From A Teacher
• Science Fair Board Ideas
• Easy Science Fair Projects

Helpful Science Resources To Get You Started

Here are a few resources that will help you introduce science more effectively to your kiddos or students and feel confident yourself when presenting materials. You’ll find helpful free printables throughout.

• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• 8 Science Books for Kids
• All About Scientists
• Free Science Worksheets
• Science Supplies List
• Science Tools for Kids
• Scientific Method for Kids
• Citizen Science Guide
• Join us in the Club

Printable Science Projects For Kids

If you’re looking to grab all of our printable science projects in one convenient place plus exclusive worksheets and bonuses like a STEAM Project pack, our Science Project Pack is what you need! Over 300+ Pages!

• 90+ classic science activities  with journal pages, supply lists, set up and process, and science information.  NEW! Activity-specific observation pages!
• Best science practices posters  and our original science method process folders for extra alternatives!
• Be a Collector activities pack  introduces kids to the world of making collections through the eyes of a scientist. What will they collect first?
• Know the Words Science vocabulary pack  includes flashcards, crosswords, and word searches that illuminate keywords in the experiments!
• My science journal writing prompts  explore what it means to be a scientist!!
• Bonus STEAM Project Pack:  Art meets science with doable projects!
• Bonus Quick Grab Packs for Biology, Earth Science, Chemistry, and Physics

15 Comments

When I click the link to go to your blog from my email, a virus (weird website) keeps popping up. I like your blog. But you may want to check into the virus.

I think Liam’s explanation of water density is perfect – smart kid! These projects are a perfect way to *show* kids the difference, instead of just trying to explain it to them (like you said, nearly impossibly for preschoolers!)

I can see salt water being a big hit around here for experimenting! This looks so fun! Pinning for the future!

Lots of stirring but lots of interesting fun! Thanks for pinning!

Thanks Emma! He’s a smart cookie and likes to see things too understand! Not big on listening a whole bunch just yet 😉

Thanks I will look and see what I can see! Glad you like it!

Very good post. I absolutely love this site. Continue the good work!

I like this experiment but it is not about weight it is about density.

Yes, I have been meaning to update it a bit more. Thank you.

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Salt Water Density Experiment

How does food coloring react to salt & fresh water.

We love experiments that are no fuss and easy! Paired with our FREE observation lab sheet, how can you go wrong! Your students get to predict what they think will happen, make observations, and then conclude why. This experiment uses simple kitchen items to mesmerize your students. We use this Salt Water Density Experiment while investigating our Earth’s Water Unit since it is an effective at displaying the difference in density between salt and fresh water.

*Don’t miss our Floating Egg Experiment with FREE lab sheets that also investigates the difference in density between fresh and salt water. Wait… there’s more! Discover how the freezing point of salt water and fresh water differ in this experiment, “Does Fresh or Salt water freeze faster?”

As a Christian Book and Amazon affiliate, we may earn commissions from qualifying purchases. Thank you for your support. As always, we only recommend items that we truly feel will benefit your homeschooling experience. We appreciate it.

Important Terms and Facts to Introduce

Before conducting the experiment, there are a few things you should cover with your students to create a meaningful learning experience. First, spend time talking about the terms below. We discuss the meaning of salinity and density amongst other terms.

– Density is the amount of mass in a given volume.

– Salt is also called Sodium Chloride.

– Salinity  describes the amount of salt dissolved in water. Saline water is water with salt dissolved in it. 

– Solution is a type of homogeneous mixture composed of two or more substances.

– Solute is a substance dissolved in another substance, known as a solvent .

– Water’s density is 1 g/ml.

Salt Water Density Experiment Observation Sheet

The Salt Water Density Experiment Observation Sheet will guide your students through predictions, observations, and give students a place to write a conclusion. Teacher will need to guide student through the experiment and science explanation.

Gather Materials

The materials list is likely to be found within your kitchen. You will need 2 clear glasses, water, salt, and food coloring. Yes, that is it!

Salt Water Density Experiment Lab Procedures

Make predictions.

We started by filling both glasses up with about 1 1/2 cups of water. To create salt water, we added 2 tablespoons of salt to one of the glasses and stirred until completely dissolved.

Next, the students made their predictions about what they thought would happen when we added the food coloring to each glass. One of mine thought that the fresh water would be lighter in color while the salt water would be darker. Two other students predicted that the food coloring would produce bubbles in the salt water.

Make Observations

The first glass we put food coloring into was the fresh water. We only put 3 drops of blue food coloring in. There is no need to stir. This is the optimum time to just observe and then draw your observations. You will notice that the food coloring drops went to the bottom of the glass.

Next, we added the drops of food coloring to the salt water. As you can tell from the next photo, it immediately stopped when it hit the saline solution. It stayed in a layer above the salt water.

Draw Conclusions

the kids and I talk about why they think the food coloring reacted the way it did. In the end, we discuss how salt added mass to the density of the water causing it to become more dense. The density of water is a little less than 1 g/ml. So, if something sinks in water, like the food coloring, it is more dense. If something floats on a liquid, like the food coloring in the salt water glass, it is less dense. 

What I find interesting though, is that if you wait thirty minutes or so, the food coloring in both glasses will disperse. This is because the density of all of the liquids are close enough that the water molecules will eventually collide and join. Liquid molecules move and slip past each other. Pretty cool, huh?

DOWNLOAD Salt Water Density Experiment Observation Sheet

More free resources.

John 4:14  – But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.

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Liquid Layers – Salt Water Density Straw

Use your knowledge of density to create a colorful rainbow inside of a drinking straw.

Print this Experiment

Density can be a difficult scientific property to grasp. With that in mind, we found a way to make the science of density a colorful, fun, and (most importantly) simple experience! This project is the epitome of kitchen science. You’ll use kitchen-safe materials to make science accessible and fun. It’s quite the kid-friendly experiment when you create a colorful experience that will have young scientists understanding density in moments.

Experiment Videos

Here's What You'll Need

Food coloring, clear drinking straws, baby soda bottles and rack (optional), let's try it.

Using small cups (9 oz works great), put 1 tsp of salt into Cup #1, 2 tsp of salt into Cup #2, 3 tsp in #3, etc. up to #6. Label each cup.

Add about 9 oz of warm water to each cup. Stir the salt and water solution until all of the salt has completely dissolved.

Use the food coloring to dye the solutions in each cup a different color. If you want to make a rainbow of colors then add the following combinations of color to each cup.

Add red to cup #1, red and a yellow to Cup #2, yellow to Cup #3, yellow and blue to Cup #4, blue to Cup #5, and blue and red tablet to Cup #6.

Carefully transfer the liquids to the six tall containers like Baby Soda Bottles, and place them in order from #1-6.

Grab a clear drinking straw. Keeping both ends open, dunk the bottom end of the straw about 1 inch into the liquid of the “1 tsp” solution. Cap the top of the straw firmly with your thumb and remove the straw from the solution.

Now that you have the first solution in the straw, dip the end of the straw into the “2 tsp” solution. This time, dip the straw about 1 inch deeper than you did into the first solution. After you’ve dipped the straw, lift your thumb and replace it.

Continue the dipping process until you have all six colored solutions inside the straw. It’s a density column of salt water!

How Does It Work

Density is the measurement of how much “stuff” is packed into a measured space. Nearly every substance and material imaginable has a different density. This is especially true for the six solutions you made using salt and water. By increasing the amount of salt in the solution but keeping the amount of water constant, you create solutions that have increasing densities. The more salt that is mixed into a measured amount of water, the higher the density of the solution. As the Density Straw shows, a solution with a low density stacks on top of a solution with a higher density.

So, density explains why the solutions stack on top of each other inside the straw, but what keeps the solutions in the straw? You might expect the solutions to just fall out of the straw as you lift the straw from a solution. However, because of cohesion (similar molecules attracting each other) and adhesion (different molecules attracting each other), there is surface tension sealing the water at the bottom of the straw. The surface tension is strong enough to help hold the solutions in the straw as long as air pressure inside the straw is lower than all the air pressure outside the straw. Gravity tugs the solutions downward which creates a slight vacuum in the empty part of the straw. That lowers the air pressure inside the straw which is why you need your thumb to cap the straw. This prevents air pressure from equalizing in the straw. If you remove your thumb, the air pressure equalizes, and gravity simply moves the colored solutions out.

Take It Further

What would happen if you added the layers to the straw in reverse order? How about if you went completely out of order and added colors from #1, then #3, then #5?

Science Fair Connection

You may have mastered the Liquid Layers experiment, but now it is time to turn this experiment into a science fair project. You can make it one simply by identifying a variable (something that might change the outcome) in the experiment, then testing that variable, and correctly reporting the results.

• Try using something besides salt. Would sugar work the same?
• Instead of using salt water, try different liquids to see if you can layer them.
• Another variation you could try would be using a different size of straw. Just remember that your thumb needs to fit over the end to create a complete seal in order for this to work.

These are just a couple of ideas, but you are not limited to just them! Come up with different ideas of variables to test and give them a try. Remember, you can only change one variable at a time for each test. For example, if you are testing different liquids, make sure that all other factors in the test remain the same!

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Elliot and the Surfing Scientist: Salt water density experiment

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ELLIOT: What you doing? What you doing? What you doing?

RUBEN: Setting up an experiment, Elliot.

ELLIOT: What you doing?

RUBEN: Well, I've got three glasses here. One with red water, one with water I've coloured yellow and one with green.

ELLIOT: I can completely see that but why? What's in them?

RUBEN: The other thing I've put in them is some table salt. I've put one tablespoon of salt in this one, two tablespoons of salt in that one.

ELLIOT: Why have you done that?

RUBEN: Density.

ELLIOT: What did you call me?

RUBEN: I just said density. What do you know about density?

ELLIOT: Uh, density is… the compactness of a substance.

RUBEN: Very good!

ELLIOT: From the dictionary.

RUBEN: Excellent. What do you know about pretty colours?

ELLIOT: Aha! I know that they're pretty, I know that they're colourful and I know that I love them!

RUBEN: Well, then you're going to love this experiment.

ELLIOT: OK, what else do we need?

RUBEN: I need a clear straw. Do you have any?

ELLIOT: Yeah. What do you want? I've got a short straw. Want that?

RUBEN: No, thanks.

ELLIOT: I've got this one. Be very careful with that one. That's the straw that broke the camel's back. And I think that's… Ruben! This is the last straw! Alright?

RUBEN: Yeah… well, can I have it?

ELLIOT: You clutch at straws, mister. Say please.

RUBEN: Please can I have the last straw?

ELLIOT: Yes, you can. Why do we need straws, by the way?

RUBEN: So we can make straw pipettes.

ELLIOT: Pipettes?

RUBEN: You know what a pipette is?

ELLIOT: Um, a groovy seed! A pipette! Hey, I'm a pipette!

RUBEN: That's great… No, a pipette is when you poke a straw into a liquid, put your thumb over the end, lift it out, you've got some liquid stuck inside.

ELLIOT: I get my milkshake and go like that! OK, why do we need pipettes?

RUBEN: Well, so we can view the density layers.

ELLIOT: Aah! What did you call me?

RUBEN: Nothing. Look, ponder this. What do you think will happen when I now dip it into the next glass, a little bit deeper, repeat, then dip it into the third glass and repeat the procedure again?

ELLIOT: OK, well, you've got those colours, I reckon they're going to mix in the straw and you're going to end up with a straw full of brownish water. But that's common sense, I reckon.

RUBEN: Well, let's see what happens, we go into the second cup, repeat the procedure. Ooh, look at that!

ELLIOT: Hey! It's yellow and red now!

RUBEN: That's right. Into the third glass and up we go. And…

ELLIOT: Check it out! Look, they're separating, slowly separating. So we've got red at the top, yellow in the middle and green at the bottom and they know not to go into each other's borders! That's amazing! Like a stack of coloured water bricks! Why's it doing that?

RUBEN: I'm glad you asked, Elliot. It's because of density, right? We've got the most dense liquid on the bottom here, and because it's heavier, as it's got more salt in it, it's got more density, it stays on the bottom. This one is the middle density, so it stays in the middle. The fresh water with just a bit of red food colouring is the least dense so it floats on top.

ELLIOT: Aah…

RUBEN: Very interesting, huh? Now, this happens in the ocean, as well. Saltier water sinks to the bottom, fresher water floats to the top and it creates these amazing currents which are called the thermohaline circulation. They push water right around the globe.

ELLIOT: Mmm, so that's the secret to the oceans.

RUBEN: Well, it's part of it, that's for sure.

ELLIOT: It's just a shame they don't do it with those colours. You know what I've learnt?

RUBEN: What's that?

ELLIOT: I've learnt that if you are ever stacking coloured water in straws, salt can be very useful.

RUBEN: Mmm, good point. Well, um, might see you next time.

ELLIOT: Yeah, yeah. I've got a trick with the straw, too. You get a little bit of paper… Oh, the Surfing Scientist is so clever! You can find him via the Spark section of RollerCoast

SUBJECTS:   Science

YEARS:  5–6

Discover what density is and how you can test the density of liquids.

In this science experiment you will find out about salt water and how its density is responsible for the circulation of water around the world's oceans.

Things to think about

• 1. What do you know about density? Can different liquids have different densities? If so, what would happen if you mixed them? Do you think adding salt to water would change the density of the water?
• 2. The liquid of which colour has the most salt added to it? Which has the least salt? What does Ruben's assistant Elliot say density is? What happens to the three liquids as they are move up into the straw? Do they mix or separate? What name does Ruben give to the ocean currents that are influenced by water density?
• 3. Explain or draw a diagram to show what you saw in the experiment. What did it tell us about the density of salt water? Do the results of this experiment help to explain why objects (including people) float better in salty water? Explain why the experiment included a water sample without any salt added, and why the liquids were coloured.
• 4. Conduct an experiment to test the flotation qualities of objects (how well they float). Use things such as paper clips and pens, in salty water. Remember, for a fair test, the objects also need to be tested in water 'without' salt. Research the deep ocean currents and find out how they influence ocean temperature and levels of nutrients and gases.

Production Date: 2008

Metadata © Australian Broadcasting Corporation and Education Services Australia Ltd 2012 (except where otherwise indicated). Digital content © Australian Broadcasting Corporation (except where otherwise indicated). Video © Australian Broadcasting Corporation (except where otherwise indicated). All images copyright their respective owners. Text © Australian Broadcasting Corporation and Education Services Australia is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0).

Elliot and the Surfing Scientist: Getting iron out of breakfast cereal

Elliot and the Surfing Scientist: Hydrogen and its properties

Elliot and the Surfing Scientist: Implode a soft drink can using an invisible force

NOTIFICATIONS

Temperature, salinity and water density.

• + Create new collection

Cold water is denser than warm water, so it tends to sink. Seawater is denser than freshwater. Salinity, temperature and depth all affect the density of seawater.

The ocean has a complex circulation system called the Global Ocean Conveyor. It moves water, heat, salt and nutrients around the world. Surface currents in the top 400 m are driven mainly by wind. Deeper currents are driven by changes in water density. Both types of currents work with the atmosphere to help shape the Earth’s climate.

Melting land ice and increased rainfall – as consequences of climate change – have the potential to disrupt the oceans’ chemical and physical properties, which will impact this complex circulation system. Learn more in the article Climate change, melting ice and sea level rise .

By the end of this activity, students should be able to:

• describe how temperature affects water density
• describe how salinity affects water density
• offer simple explanations of how climate change may impact the oceans’ chemical and physical properties.

Download the Word file (see link below) for:

• background information for teachers
• equipment list
• teacher instructions
• extension ideas/prompting questions for teachers.

Nature of science

In science, models are a visual way of linking theory with experiment. In this activity, students are able to visualise differences in water density. This fits into the investigating in science aspect of the NZC.

Related content

Explore the big ideas that underpin floating and sinking in the article Building Science Concepts: Floating and sinking .

Read the articles Ocean salinity and Ocean density to learn about the vital role salinity and density play in ocean currents and heat circulation.

Activity ideas

Floating eggs – students investigate water density by floating an egg in freshwater and saltwater.

Buoyancy in water – students make a Cartesian diver to demonstrate the relationship between volume, mass and density.

Investigating seawater – students investigate some of the properties of seawater.

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Science Projects > Physics & Engineering Projects > Saltwater Density Science Project  

Saltwater Density Science Project

If you have the advantage of visiting the ocean or the Great Salt Lake in Utah this summer, you may find your swimming experience in these bodies of water to be slightly different than swimming in a freshwater lake or river. If you accidentally get water in your mouth or eyes from the ocean or the Great Salt Lake, you will certainly notice the saltiness of the water. But what about floating? Is it easier to float in the ocean or Great Salt Lake than in freshwater? And if there is a difference in your ability to float, do you think that water from one body of water is denser than water from another body of water? Which do you think is the most dense? Freshwater from a lake, saltwater from the ocean, or saltwater from the Great Salt Lake? Do this saltwater density experiment to find out!

What You Need:

• 3 test tubes (or use 3 jars instead)
• Jar, drinking glass, or beaker (for making the salt solutions)
• Salt (you can use just regular table salt)
• Medicine dropper
• Red, blue, and yellow food coloring
• Graduated cylinder
• Measuring cup or beaker that measures in 10’s of ml

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What You Do:

2. Fill the dropper with water from the “Great Salt Lake” test tube, and add it to the graduated cylinder. You may need to add two or three droppers full of water to the cylinder.

3. Rinse the dropper out really well with faucet water to avoid cross contamination of salt and food coloring.

4. Fill the dropper with water from the “ocean” test tube. This time, very gently and carefully add it to the graduated cylinder so that the force of the water being squeezed out of the dropper doesn’t mix the two waters. Add about the same amount of “ocean water” to the graduated cylinder as there is “Great Salt Lake water.” Rinse out the dropper with faucet water.

5. Fill the dropper with water from the “freshwater” test tube. Again, add the water very gently to the water already in the graduated cylinder to avoid mixing the water, and add about the same amount of freshwater as “ocean water.”

What Happened:

Density is the measure of how much matter (mass) is packed into an item or material compared to the amount of space (volume) it takes up. A material that is more dense (e.g. lead) will weigh more than a material that is less dense (e.g. cork) even though they both take up the same amount of space. Or, to think of density another way, 10 pounds of cork takes up a lot more space than 10 pounds of lead.

To really prove that the “Great Salt Lake water” is the most dense, the freshwater is the least dense, and the “ocean water” has a density somewhere in between these two types of water, try this experiment again except this time reverse the order that the solutions were placed in the graduated cylinder. Do they sit on top of each other as they did before or do they mix up?

More Water Projects:

• Surface Tension

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Exploring Our Fluid Earth

Teaching science as inquiry.

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Further Investigations: Density, Temperature, and Salinity

Fig. 2.7. Create water layers by pouring water of a different temperature or salinity slowly down a stirring rod.

Image by Byron Inouye

  1. Simulate layers of water formed by differences in temperature and salinity.

Prepare two 100 mL water samples, one of cold salt water and the other of warm fresh water. Add a different color of food coloring to each.

Place the cold salt water into a beaker. To prevent mixing, slowly pour about 20 mL of the warm fresh water down a stirring rod or down the back of a spoon onto the cold salt water in the beaker (Fig. 2.7). Look for evidence of layering.

Test different combinations of water temperature and salinity.

Try to create three or more water layers in your beaker.

2. What do you think the relative density of the bag alone (empty of liquid) is in the Density Bags Activity ? How might the density of the bag affect the results? Design an experiment to test your hypothesis.

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April 10, 2014

Salty Science: Floating Eggs in Water

A density demonstration from Science Buddies

By Science Buddies

Key concepts Density Mass Volume Concentration Buoyancy Water Introduction Have you ever wondered why some objects float in water and others sink? It has to do with the density of the objects compared with the density of the water surrounding them. If an object is less dense than the water around it, it will float. Because salt water is denser than freshwater, some things float more easily in the ocean—or extremely salty bodies of the water, such as the Dead Sea. You can make your own dense water by adding salt to tap water. In fact, if you add enough salt, you can make the water so dense that an egg will actually float in it! Explore how this works in this science activity.   Background If you put an egg in a cup of tap water, it will sink to the bottom. Why is this? Because the density of the egg is higher than the density of tap water, so it sinks. Density is the mass of a material per unit volume. For example, the density of freshwater under standard conditions is approximately one gram per cubic centimeter.   But, if you add enough salt to the water, the egg will actually float back up to the surface! Adding salt to the water increases the density of the solution because the salt increases the mass without changing the volume very much.   When enough salt is added to the water, the saltwater solution's density becomes higher than the egg's, so the egg will then float! The ability of something, like the egg, to float in water or some other liquid is known as buoyancy. But just how much salt is needed to make an egg float? In this science activity you'll figure that out by making solutions with varying concentrations of salt in them.   Materials

Measuring cup

Large container, such as a large bowl or cooking pot (It must be able to hold at least three cups.)

One half cup of table salt

Five cups that hold at least 16 ounces each

Permanent marker (if you are using plastic cups) or masking tape and a pen (to label nondisposable cups)

Three spoons for mixing salty solutions

Soup spoon for egg transfers

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  Preparation

Take the egg out of the refrigerator and allow it to warm to room temperature. Be sure to always wash your hands after handling uncooked eggs because they may carry salmonella.

Pour one and one half cups of water into your large container.

Add one half cup of salt to the large container and stir to dissolve some of the salt (it will not all dissolve yet).

Add one more cup of water to the large container (making two and one half cups total) and stir to dissolve the remaining salt. The salt should be completely dissolved before you go on to the next step. It may take several (five to 10) minutes of stirring, so you may need to be patient. Why do you think it's important to start out with a solution that has such a high concentration of salt?

Arrange the five cups on a surface, going in a line from left to right. Label the cups 1 to 5. If you are using plastic cups, you can use a permanent marker to label them. If you are using nondisposable cups, you can use masking tape and a pen to label them.

Add three quarters cup of the salty solution you prepared to cup 1.

Add three quarters cup of plain tap water to cups 2 through 5. (Cup 5 will be plain tap water.)

Add three quarters cup of the salty solution you prepared to cup 2 and mix it. What is the salt concentration in cup two compared with cup one?

Add three quarters cup of the salt solution from cup 2 to cup 3 and mix it. What is the salt concentration in cup 3 compared with cups 1 and 2?

Add three quarters cup of the salt solution from cup 3 to cup 4 and mix it. What is the salt concentration in cup 4 compared with the other cups?

Use a soup spoon to place an egg in cup 5. Does the egg float?

Use the spoon to take the egg out and place it in cup 4. Does the egg float?

Repeat this process with cups 3, 2 and then 1. In which cup does the egg first float? If the egg floated in more than one cup, did you notice any difference in how it floated? What does this tell you about the density of the egg?

Extra: In this science activity you figured out, within a factor of two, how much salt it takes to float an egg. You could narrow down the range further by testing additional saltwater solutions to try and determine the egg’s density. To do this, start your solution with the salt concentration in which the egg first floated and make a new dilution series, as you did before. Now in which cup does the egg first float? What does this tell you about the density of the egg?

Extra: Repeat this activity using several more eggs, possibly both hard-boiled and uncooked eggs. Do you get the same results with other eggs or is there some variation between different eggs? For testing hard-boiled versus raw eggs, you should test the same egg, first raw and then after hard-boiling it to investigate any differences.

Extra: Find out how much salt there is in seawater. From the results of your activity, do you think an egg would float or sink in seawater?

 [break] Observations and results Did the egg float in cup 1 and 2, but not in cups 3, 4 or 5?   You likely saw that the egg floated best in cup 1, floated a little less in cup 2 (but part of it was above the surface) and did not float in the other cups. Cup 1 had the undiluted salty solution that you originally prepared, which was one half cup of salt in two and one half cups water total. The concentrations of the salt solutions in cups 2 to 4 were halved as you increased in cup number; for example, the concentration of the salt in cup 2 was half that of cup 1, and the concentration of the salt in cup 3 was half again of cup 2. (Cup 5 had plain tap water.) The egg should have sunk in cups 3, 4 and 5 because the density of the egg was higher than the density of the solutions (or plain tap water) in those cups. Cups 1 and 2 had more salt in them than the other cups (with cup 1 having the most salt), which means these solutions were denser. The egg should have floated (with part of it above the water surface) in these two cups because the solutions were denser than the egg. The actual density of the egg is in between the density of the solution in cup 3 and that in cup 2.   More to explore What Is Density? , from Charles E. Ophardt, Elmhurst College Why Is the Ocean Salty? , from Herbert Swenson, U.S. Geological Survey Publication Fun, Science Activities for You and Your Family , from Science Buddies How Salty Does the Sea Have to Be for an Egg to Float? , from Science Buddies

This activity brought to you in partnership with Science Buddies

20 Surprising Science Experiments with Salt (Kids Will Love Them)

• October 23, 2020
• Science Experiments

Our houses have many ingredients that serves as a key component for performing a lot many simple science experiments.

I am sure, you would never imagine how useful SALT can be around your home to engage your kids with fun learning and to explore the world of science around you and your kids.

Science Experiments with Salt

All the experiments are super fun, simple, easy to do, no messy, easy to set up, and especially unique science activities. Here we go!

1. Salt Painting Science Experiment

If you are looking for a simple science and art project , then this awesome salt painting science experiment is a great way to explore about simple concepts of science such as absorption. Pre-schoolers and home schoolers find this experiment a great way to learn science concepts.

Find more details of this amazing science experiment here: Salt Painting Science Experiment

2. Desalinization Science Experiment

The word ‘Desalinisation’ is an intimidating word for young children. But believe me, with this spectacular science experiment kids easily learn marine biology hands-on.

Supplies and instructions for desalinisation are found here: Desalinisation Science Experiment

3. Floating Egg Science Experiment

What happens to an egg placed in the salt water? Did you know that an egg can be floated in the water? Simple salt water experiment to teach kids about density and fresh water in a fun and entertaining way. Awesome kitchen science experiment for children of grades 1-5.

Are you interested in learning the complete instructions of the experiment? Click on Floating Egg Science Experiment

4. Make Ice-Cream in a Bag Science Activity

Kids will love to make their own ice creams and end up with a great tasting desert while learning a lot of chemistry science . This is such an awesome kitchen science experiment that finishes in 10 minutes . How cool is it!!

Engage your kids in making ice cream with complete instructions. Find details here: Make Ice-Cream in a Bag Science Activity

5. Melting Ice Salt Science Experiment

Children will learn how salt melts ice with this super cool science activity. It seems simple and easy but encourage kids to explore a lot of science.

Do not miss to check out Melting Ice Salt Science Experiment for more information in detail.  

6. Grow Salt Crystals Science Activity

Growing salt crystals is a simple science experiment that is popular to make kids learn about chemical reactions involved to form crystals. Fun and engaging Easter Science Activity! Kids will have a ton of fun while learning how to grow salt crystals at the same time.

Get more details of the experiment here: Grow Salt Crystals Science Activity

7 . Ice and Salt Science Experiment

Here is an awesome science activity fills the days of the children in grades 1-7 with some simple science concepts. It’s a fun STEAM (science, technology, engineering, art, Math) activity for kids.

Check out here, Ice and Salt Science Experiment

8. Sticky Ice Science Experiment

This kid’s friendly science experiment with ice is simply too cool, quick, easy, and little magical. Kids will get to learn about freezing point of water and its effects on salt in a fun way. Challenge your children to lift the ice cube just using a thread!  

Click here Sticky Ice Science Experiment to learn full description of this super classic science experiment.

9. Egg Geodes Science Experiment

Fun and successful science fair project with egg geodes make the children sharp in developing their critical thinking and questioning skills leaving a wow factor on their faces.

Want to give it a try!? Click on Egg Geodes Science Experiment .

10. Homemade Slushy Drink with Ice and Salt Experiment

Let your kids learn about freezing and melting points while having fun in making homemade slushy drink on their own. This simple science activity offers a great alternate method of making ice cream and cooling drinks very quickly. Sounds entertaining!!

Get the complete description about this classic science experiment here: Homemade Slushy Drink with Ice and Salt Experiment

11. Salt Vibrations STEAM Activity

Here on it is not intimidating to understand the concept of sounds. Easy and fun science STEAM activity that teaches kids about sounds caused by vibrations. In fact, kids are allowed to enjoy this demonstration that actually shows kids the sound waves in action. Click on Salt Vibrations STEAM Activity

12. Salt Water Experiment Ocean Science

A terrific salt science experiment for pre-schoolers! An awesome kitchen science experiment to teach kids about density of salt water versus fresh water. This experiment offers great time to learn about the difference between fresh river water and salty ocean water. What a cool activity!

Click on Salt Water Experiment Ocean Science to find more details

13. Growing Gummy Bears Science Experiment

Have you ever wondered of watching growing gummy bears? Do you think it is hard to witness? Absolutely not! Do this simple science experiment to show how this common kitchen hold mineral effects gummy bears?

Check out here to find simple step-by-step information and instructions: Growing Gummy Bears Science Experiment

1 4 . Rainbow Salt Circuit Science Experiment

Creating an electric circuit using common kitchen hold mineral i.e. salt is an amazing experience for the kids. A great hands-on examination on circuits making kids scientific knowledge on power and circuits little more interesting and exciting.

Are you interested in creating your own salt circuit with water? Then click on Rainbow Salt Circuit Science Experiment

15. Cleaning Pennies Science Experiment

All the kids love to play with pennies and while playing they even observed at times some pennies look dull and some other look bright. Just remind your children about this and ask them to guess what the reason behind that is. Let them explain their versions and then explain them about this cool science experiment. They love to do this hands-on activity to watch the magical results of cleaning pennies. Just browse Cleaning Pennies Science Experiment

16. Salt Pendulum Science Experiment

Salt pendulum is a fun art and science fair project for kids of all ages. Let your kids explore the science behind changing times and pendulums hands-on. While investigating the experiment ask your child to predict the time according to the movements of pendulums and predict what impacts time change. Also help them to understand the concept by explaining how salt effects this experiment in a fun way.

Find more details of the experiment here: Salt Pendulum Science Experiment

17. Popcorn and Salt Science Experiment

Let your kiddos think about their own scientific thought process with this easy and simple science activity to do with salt and popcorns. Using just three ingredients you can bring a lot of change in your child’s scientific knowledge. Easy to set up experiment with great results, highlights the difference between mass and volume using kid’s most favourite snack.

Are you ready to experiment with popcorns and salt : Popcorn and Salt Science Experiment

18. Lava Lamp Cool Science Experiment

An excellent way to explore density of liquids using simple ingredients you have right in your kitchen. Fun way to explore density of liquids and great opportunity to practice mixing colors. Besides, this is an easy going science and sensory play experiment as it makes children much more excited and attentive to study the simple science concepts using salt.

Click on Lava Lamp Cool Science Experiment for more information.

19. Static Electricity Balloon and Salt and Pepper Experiment

Children might have observed a balloon sticking to something like hair strands, comb, salt, etc.  Throw a question to your children on the magical science involved in this process of sticking to things. Static Electricity Balloon and Salt and Pepper experiment is all about explaining static electricity in a fun way. Isn’t it excited? Best and simple science experiment for your elementary children : Static Electricity Balloon and Salt and Pepper Experiment

20. Solid-Solid Separation science Experiment

An amazing easy fun science activity that teaches kids to understand about three science concepts i.e. evaporation, sedimentation, and filtration. How amazing is it to explain the three main science concepts while performing a single science investigation.

Click on Solid-Solid Separation science Experiment

So, here are the simple and easy science experiments to do with common kitchen hold mineral, salt. There is a lot of science involved in these super cool experiments that will surely amaze you and your kids. Simple science experiments that everyone will love! Fun and fascinating experiments for toddlers , pre-schoolers, and even some are perfect for older kids. Have a look and enjoy experimenting with salt. Happy Experimenting!!

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Temperature, Salinity and Water Density Activity

The University of Waikato Te Whare Wānanga o Waikato, Science Learning Hub Pokapū Akoranga Pūtaiao

This is a simple but effective scientific experiment to study the impacts of temperature and salinity on water density.

Notes from our reviewers

The CLEAN collection is hand-picked and rigorously reviewed for scientific accuracy and classroom effectiveness. Read what our review team had to say about this resource below or learn more about how CLEAN reviews teaching materials .

• Teaching Tips This activity can range in duration depending on class size, resources, and teacher choice. For older students (fourth grade and up) this activity could be done at home and shared about in class using a flipped classroom model. This could be an introduction to density topics, oceanography, chemistry, etc. With more materials and time the kids could do it themselves, which would be better.
• About the Science A study in temperature, salinity and water density using ice cubes, glasses of water and food coloring. Scientific accuracy is high, and there is enough background information for the teachers to understand the topic. Passed initial science review - expert science review pending.
• About the Pedagogy The activity described here should be interesting and engaging for students. It may be helpful to set up multiple versions of this if you have a larger class that could have trouble observing the results as a group. Includes end goals for the lesson, background information for the teachers, instructions and extension ideas/question prompts for the lesson.
• Technical Details/Ease of Use While this is a simple experiment, it does require some set-up and materials. Teachers should read through and prepare beforehand. Minimal prep is needed to freeze the ice with food coloring. Most materials that are readily available in elementary classrooms. You only need a few drops of food coloring and salt. A camera is mentioned but not necessarily required.

Lesson Plans

Modeling salinity and deep ocean currents.

In this experiment, students make a claim about the cause of ocean currents and then develop a model to explain the role of salinity and density in deep ocean currents.  This lesson is modified from "Visit to an Ocean Planet" Caltech and NASA/Jet Propulsion Laboratory.

Materials Required

• 4 Baby food jars 
• 2 Laminated index cards 
• ½ cup Table salt
• 2 Colors of food coloring (red and blue)
• 1 Stir stick
• Dishpan (for spills)
• Map of surface currents
• Map of surface salinities 
• Optional: aprons 
• Student Data Sheet

PREPARATION 

• It is important to do this activity before your students do it. This will give you a chance to see and work out any potential problems beforehand. Gather the supplies or send a supply list home with the students. Make sure that the students mark their names on anything they bring to class that will be returned home.

Engage the Learner:

Display the maps of surface ocean currents and surface salinities of the oceans [Figs. 1 & 2].  

Have the students look for relationships between salinity and the locations of warm and cold currents. 

Distribute the Student Sheet.  Direct students to write their observations down on Student Sheet in the Initial (Quantitative/Qualitative) Observations section.  

Asking Questions:

• Next, have students brainstorm questions that come to mind about these data and how they may be related.  Students write their questions in the Your Questions section.
• Guide students through the process of generating a claim statement.  Ask the students to write a claim that addresses these relationships in the Claim Statement section.  Example., Surface currents control the water’s salinity.  

 Carrying Out the Investigation:

First model the experiment for the students before having them conduct the investigation with their group:

• Fill both baby food jars with water of the same temperature. Note to students the parts of the experiment that you are holding constant:  jars, amount of water, the temperature of the water, etc. 
• Dissolve ¼ salt in one of the jars and add blue food coloring. Make sure to mark the jar “Salt Water.” 
• Add three drops of red food coloring to the other jar and label it “Fresh Water.” 
• Place a 3 x 5 index card (laminated, preferred) on top of the saltwater and carefully & quickly invert it. Place the saltwater jar on top of the freshwater container and have someone carefully remove the card. 
• Observe the results. 
• Use the second set of jars to repeat the experiment. 
• This time, invert the freshwater jar over the saltwater jar. Remove the card, and observe the results. 
• Take both sets of jars, turn horizontally, remove the card and observe the results. 

Analyzing the Results:

• Allow time for students to document their observations in the Evidence section of the dataset.
• Students observations should include the following:
• When the saltwater is placed on top of the freshwater, the water in the two jars will mix and the saltwater will sink to the bottom. 
• When the freshwater is placed on top of the saltwater, the freshwater will sit on top of the salty water and no mixing will occur.

Interpreting Data: 

Provide the following questions to help students with their observations/evidence:

• Describe how the salt and freshwater moved in the experiment?  Saline water sunk to the bottom, under fresh water.
• Why does the salty water sink?  It is denser (has more molecules in the same amount of space).

Explain The Results:

Facilitate a discussion based on the following points:

• The greater the amount of salt in the water,  the higher its density will be because there are more molecules found in the jar. The saltwater will be heavier than the freshwater so when salt water is placed on top of freshwater the two will mix and the saltwater will sink to the bottom. When freshwater is placed on top of saltwater the higher density water is already on the bottom and is held there by gravity so no mixing occurs. 
• This model displays the movement of water based on its salinity, especially in the deep ocean.  When salty water sinks deeper through the water column because of its greater density, deep ocean currents are formed as the water moves horizontally and travels from areas of high salinity to those that are less salty.  The salinity of the water may increase due to evaporation or freezing of water into sea ice at the poles.
• Queue the Sea Surface Temperature animation.  Explain the color bar used in the following animation shows the long term average sea surface salinity, where white regions have the highest salinity and dark regions the lowest. 
• Students will observe the video and look for locations that show patterns of higher salinity regions vs low.  
• Run the video of Sea Surface Salinity. 

Video: NASA Sea Surface Salinity

NASA Sea Surface Salinity | https://www.youtube.com/watch?v=D_OAhjDo78A | Source: NASA Goddard and NASA's Earth Observatory

• Discuss the key findings. Students should observe the higher salinity values of the Atlantic than the Pacific.  This is due to the greater rainfall amounts in the Pacific, and the lower salinity at the mouths of major rivers.

Display the following image, drawing students' attention to the Atlantic Ocean basin.  

• Ask what is happening here?  The Atlantic features a circulation pattern of warm surface currents, including the Gulf Stream, that brings warm surface waters from the tropics northward into the North Atlantic. There, in the seas surrounding Greenland, the water cools; sea ice forms removing freshwater from the water making it denser, sinking to great depths and changes direction. What was once warm surface water heading north turns into cold deep water going south. This overturning is one part of the vast conveyor belt of ocean currents that move heat around the globe.
• Present the following question to the students:  What effect may increasing air temperatures have on this conveyor belt that distributes heat around the world?  Increasing air temperatures will cause an increase in the melting of land and sea ice in the polar regions.  This would release more freshwater into the polar regions and may affect the salinity-driven deep water circulation.

Constructing Explanations:

Engage students in a discussion around the following questions/tasks:  

• What water is heavier: salt or freshwater?   Saltwater
• Which has the greatest density (the amount of “stuff” in a given amount of space)?  Explain. Saltwater has a greater density because it has a greater amount of “stuff” (mass) in its volume. The saltwater has the water plus the dissolved salt, while freshwater does not contain the extra “stuff” (mass) of the dissolved salt. 
• Where do you expect to find the most saline ocean water?  Deep ocean
• What may explain why the surface waters at the poles have lower salinity values?   The more saline waters sink to the deep ocean.
• What explains why the surface salinity values (Figure 2.) are so high at the equator and mid latitudes?  Students may say that the water is warmer; the sun’s radiation is more intense at the equator; there is greater evaporation in this area.  
• How does our understanding of the science processes affecting the movement of water in the oceans based on their salinity values relate to their Claim Statement.  
• Is your Claim supported by your evidence and backed by our scientific understanding of the ocean circulation?  Why or Why Not?
• Have students share their Claim Statements with the class and how their deeper dive into salinity-driven currents have changed their understanding of the Hydrosphere.

Supported NGSS Performance Expectations

• MS-ESS2-1: Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.
• MS-ESS2-4: Develop a model to describe the cycling of water through Earth's systems driven by energy from the Sun and the force of gravity.
• HS-ESS2-2: Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems.

Learning Objectives

The Student will:

• Develop a claim about the cause of ocean currents
• Model to explain the connection between salinity and density in ocean currents.

Essential Questions

• How do ocean properties affect the movement of water?

Teacher Background Information

The oceans are mostly composed of warm salty water near the surface over cold, less salty water in the ocean depths. These two regions don't mix except in certain special areas. The ocean currents, the movement of the ocean in the surface layer, are driven mostly by the wind. In certain areas near the polar oceans, the colder surface water also gets saltier due to evaporation or sea ice formation. In these regions, the surface water becomes dense enough to sink to the ocean depths. This pumping of surface water into the deep ocean forces the deep water to move horizontally until it can find an area on the world where it can rise back to the surface and close the current loop. This usually occurs in the equatorial ocean, mostly in the Pacific and Indian Oceans. This very large, slow current is called the thermohaline circulation because it is caused by temperature and salinity (haline) variations.

Video: NASA: The Thermohaline Circulation (The Great Ocean Conveyor Belt)

NASA: The Thermohaline Circulation (The Great Ocean Conveyor Belt) | https://www.youtube.com/watch?v=3niR_-Kv4SM | Source: DJX Atlanta

This animation shows one of the major regions where this pumping occurs, the North Atlantic Ocean around Greenland, Iceland, and the North Sea. The surface ocean current brings new water to this region from the South Atlantic via the Gulf Stream and the water returns to the South Atlantic via the North Atlantic Deep Water current. The continual influx of warm water into the North Atlantic polar ocean keeps the regions around Iceland and southern Greenland mostly free of sea ice year-round.

The animation also shows another feature of the global ocean circulation: the Antarctic Circumpolar Current. The region around latitude 60 south is the only part of the Earth where the ocean can flow all the way around the world with no land in the way. As a result, both the surface and deep waters flow from west to east around Antarctica. This circumpolar motion links the world's oceans and allows the deep water circulation from the Atlantic to rise in the Indian and Pacific Oceans and the surface circulation to close with the northward flow in the Atlantic.

The color on the world's oceans at the beginning of this animation represents surface water density, with dark regions being most dense and light regions being least dense (see the animation Sea Surface Temperature, Salinity and Density). The depths of the oceans are highly exaggerated to better illustrate the differences between the surface flows and deep water flows. The actual flows in this model are based on current theories of the thermohaline circulation rather than actual data. The thermohaline circulation is a very slow moving current that can be difficult to distinguish from general ocean circulation. Therefore, it is difficult to measure or simulate. 

Prerequisites Student Knowledge

• Ability to read maps
• Knowledge of safety procedures while conducting science experiments and models
• Basic understanding of density

Student Misconception

• Earth’s oceans are separate individual bodies of water and are not connected.

Why Does NASA Study This Phenomenon?

Salt plays an important role in how the Earth system functions. It flows through Earth's ocean, the lifeblood of Earth's climate system. The ocean is roughly 3.5% salt and the concentration of dissolved salts in the ocean is referred to as salinity, which varies across the globe and over time. Just as too much or too little salt in our diets affects our health, so too do high and low salinity have profound effects on how the ocean circulates, how freshwater cycles around Earth and how our climate works. The concentration of salt on the ocean surface — the part of the ocean that actively exchanges water and heat with Earth's atmosphere — is a critical driver of ocean processes and climate variability.  To better understand the regional and global processes that link variations in ocean salinity to changes in the global water cycle - and how these variations influence ocean circulation and climate - NASA built and launched Aquarius , the primary instrument aboard the international Aquarius/Satélite de Aplicaciones Científicas (SAC)-D observatory. 

Video: ScienceCasts: Power of Sea Salt

ScienceCasts: Power of Sea Salt | https://www.youtube.com/watch?v=rLro_IaxZvM | Source: NASA Science Mission Directorate

STEM Career Connections

• Biological oceanographers  and marine biologists study plants and animals in the marine environment. They are interested in the numbers of marine organisms and how these organisms develop, relate to one another, adapt to their environment, and interact with it. To accomplish their work, they may use field observations, computer models, or laboratory and field experiments.
• Chemical oceanographers  and marine chemists study the composition of seawater, its processes and cycles, and the chemical interaction of seawater with the atmosphere and seafloor. Their work may include analysis of seawater components, the effects of pollutants, and the impacts of chemical processes on marine organisms. They may also use chemistry to understand how ocean currents move seawater around the globe and how the ocean affects climate or to identify potentially beneficial ocean resources such as natural products that can be used as medicines.
• Geological oceanographers  and marine geologists explore the ocean floor and the processes that form its mountains, canyons, and valleys. Through sampling, they look at millions of years of history of sea-floor spreading, plate tectonics, and oceanic circulation and climates. They also examine volcanic processes, mantle circulation, hydrothermal circulation, magma genesis, and crustal formation. The results of their work help us understand the processes that created the ocean basins and the interactions between the ocean and the seafloor.
• Physical oceanographers  study the physical conditions and physical processes within the ocean such as waves, currents, eddies, gyres and tides; the transport of sand on and off beaches; coastal erosion; and the interactions of the atmosphere and the ocean. They examine deep currents, the ocean-atmosphere relationship that influences weather and climate, the transmission of light and sound through water, and the ocean's interactions with its boundaries at the seafloor and the coast.

Technology Requirements

• Internet Required
• Teacher computer/projector only

Complementary Lesson Plans

Modeling temperature and deep ocean currents.

• Graphing Sea Level Slopes and Surface Currents

Inferring Relationships Among Sea Surface Salinity & Other Variables in the North Atlantic

Complementary Mini Lessons

Ocean surface salinity data analysis.

Tracking Monthly Salinity Changes in Our Ocean

Energy and matter: exploring ocean salinity.

Complementary Interactives

Ocean circulation patterns: garbage patches story map.

Students make a claim about the cause of ocean currents and then develop a model to explain the role of salinity and density in deep ocean currents.  This lesson is modified from "Visit to an Ocean Planet" Caltech and NASA/Jet Propulsion Laboratory.

Student Resources

•     Student Sheets
•     Original NASA Lesson - SALINITY AND DEEP OCEAN CURRENTS

My NASA Data Visualization Tool

• Earth System Data Explorer

Related Resources

• Historical Ocean Density Data: Annual Mean Data
• Ocean Circulation
• Instructional Strategies for the Earth Science Classroom

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Science project, salinity & water density.

Cold water is denser than warm water. Water with a high salt concentration ( salinity ) is denser than water that has a lower salt concentration. Warm water rises above denser colder water, and bodies of water that have different temperatures can form layers according to their respective temperatures. Likewise, denser water with high salinity sinks below water with low salinity.

How does the addition of salt to hot water affect its mixing with colder water?

• Wide mouth quart jar
• Kitchen spoon
• Food coloring
• Drinking glasses
• Thermometer
• Read about the effects of temperature and salinity on ocean water circulation.
• Formulate a hypothesis to explain how differences in salinity affect the circulation of hot and cold water.
• Have ready a 1 quart wide mouth (clear glass) jar.
• Add 8 oz. of room temperature tap water to the jar. Measure the temperature.
• Heat another 8 oz. sample of tap water until it is warm. Measure the temperature.
• Add several drops of food coloring to the warm water and stir it around.
• Carefully pour the warm water into a kitchen spoon placed over the jar, and allow the hot water to slowly spill over from the spoon into the jar.
• Note whether the colored warm water mixes or forms a layer with the uncolored room temperature water.
• Empty the jar, and add 8 oz. of room-temperature tap water to it.
• Heat another 8 oz. sample of tap water to the same temperature used in the first part of the experiment. Add food coloring.
• Add 1/2 teaspoon of salt to the warm water and stir the solution until the salt dissolves.
• Carefully pour the warm salt water into the jar containing the room temperature tap water using the kitchen spoon to slow the transfer. Note any layering or mixing behavior.
• Repeat these steps, gradually adding more salt to the hot water used in the experiment until complete mixing is observed.
• Repeat the entire experiment, using warm water at a different temperatures.
• Prepare a table comparing the amount of salt dissolved in the hot water with the amount of mixing observed for different temperatures.

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