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    Home » Science Experiments for Kids » Chemistry » What is Density?

    What is Density?

    May 25, 2022 By Emma Vanstone 11 Comments

    Density can be a tricky concept to grasp. Density refers to how much mass there is in a particular space. Imagine a drawer full of socks. It has a specific density. Suppose you take a sock out, the density of the drawer changes. This is because the mass of the socks has changed, but the volume of the drawer has stayed the same.

    Generally, the greater the density of an object, the heavier it feels.

    Solid substances are denser than their liquid and gas counterparts as the particles in a solid are much more closely packed together.

    What is Density?

    The density of an object is found by dividing the mass of the object by its volume.

    Density Formula

    Density = Mass divided by volume

    The units used vary depending on the units of mass and volume used for the calculation.

    If the mass is measured in kg and volume in cm³, the units for density would be in kg/cm³.

    Something else that can be confusing is mass. People often talk about weight when they mean mass and vice versa.

    What is mass?

    Mass is a measure of how much matter an object is made up of. The mass of an object remains constant unless you add to or remove part of it.

    The weight of an object depends on gravity. Your weight would be less on the moon as there is less gravity, but your mass would stay the same.

    You can do lots of very cool demonstrations to demonstrate density in a fun, hands-on way.  

    Density Demonstrations for Kids

    These easy density demonstrations are super simple and brilliant fun ways to show kids ( and grown-ups) this tricky concept in action. There are also a couple of nifty tricks too!

    How to make a Density Jar

    Liquids layered on top of each other to make a colourful density column #densityjar #densitytower #densitycolumn #densitydemonstration
    honey, golden syrup ( or corn syrup ), washing up liquid ( dish soap ), water and food colouring, vegetable oil

    Image taken from This IS Rocket Science

    What you need to make a density column

    Vegetable or sunflower oil

    Water

    Food Colouring

    Washing up liquid

    Honey

    Golden Syrup

    LEGO or other small objects.

    How to make a density column

    First, make a very simple version using just oil and water.

    • Pour some water carefully into a glass or jar.
    • Very carefully add about the same volume of cooking oil on top.
    • Carefully drop a couple of small objects into the mixture and observe what happens. Can you find an object to float on each layer?

    What happens if you shake the jar? You should find that the oil and water mix up and then separate again.

    Very simple density jar made with oil and water. A copper coin is at the bottom of the jar, a red lego brick floats on the water layer and a toy spider floats on the top oil layer.
    Simple density column

    To make a density column with more layers like the one above, you need lots of different liquids of different densities.

    We used: honey, golden syrup ( or corn syrup ), washing up liquid ( dish soap ), water and food colouring, and vegetable oil, in that order.

    Density Column Instructions

    Density of Liquids

    Each of the liquids has a different mass of molecules or different numbers of parts squashed into the same volume of liquid; this makes them have different densities. Therefore, one can sit on top of the other – the more dense a liquid is the heavier it is.

    Objects and liquids float on liquids of a higher density and sink through liquids of lower density. The LEGO brick falls through the oil but floats on the water, while the coin sinks through both. The coin is therefore more dense than both the oil and the water. The plastic bug floating on the oil is less dense than both.

    More Density Experiments

    Homemade Lava Lamp

    Homemade Lava lamps are a fun activity demonstrating that oil and water don’t mix.

    Homemade lava lamp to demonstrate density.

    Density Trick using Salt and Water

    Show your friends a science magic trick and a fantastic density demonstration. This activity uses salt to change the density of one colour of the water.

    Two glasses on top of each other filled with water, food colouring and different amount of salt. One colour floats on top of the other.  Salt and water density trick

    We also have a pirate themed density bottle. Pirate treasure is perfect for hiding in the layers.

    underwater themed density bottle - amde with blue water and oil

    Density and Floating Activities

    Did you know that if you reduce the density of an object that sinks in water, it will float? We tried this with a heavy ball and used bubble wrap to make it less dense. The addition of the bubble wrap made the ball float!

    two balls in a large cylindrical container. One ball sinks, but then floats when wrapped in bubble wrap to reduce the density

    You can also use the same logic to make a lemon sink or an egg float!

    Collage of density experiments. A layered density jar and an egg floating in water

    Science Concepts

    • Density
    • Mass
    • Volume
    • Sinking
    • Floating

    More Awesome Science Experiments for Kids

    Don’t forget we have 100s more fun and exciting science experiments for kids on Science Sparks.

    Some of my favourites are our Fairy Tale Activities, where you can make a raft for the Billy Goats and a Zip Line for Jack and the Beanstalk. The infamous coke and mento explosion is always great fun to watch, and our water science experiments will keep you busy for weeks!

    Wherever your interests lie, you’re sure to find something you like in our vast collection of science experiments and investigations.

    Science Books from Science Sparks

    I also have a couple of science books available you might like!

    This IS Rocket Science

    This Is Rocket Science includes 70 fun experiments for kids (and adults ) showing you how to use everyday items like bottles, cardboard, glue and tape to build excellent rocket ships, paper spinners and mobile rocket launch pads, all while learning about the scientific concepts behind space travel.

    Image of This Is Rocket Science book
    This IS Rocket Science

    Snackable Science

    Snackable Science contains 60 edible experiments allowing kids to investigate their way around the kitchen, making magical mixtures, edible Jenga and Tetris, finding the perfect ketchup and even creating their own super sour candy powder. It’s colourful, inviting and just brilliant fun.

    Snackable Science Experiments for kids - edible science book

    Last Updated on January 5, 2023 by Emma Vanstone

    « DIY Space Camp – Space Science for Kids
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    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

    Comments

    1. Actually Mummy...

      September 07, 2012 at 7:38 pm

      Oooooh! So that was it! *hunts for rainbow glass tutorial!*

      Reply
    2. Bethany @ No Twiddle Twaddle

      September 08, 2012 at 12:05 am

      Fun! We need to do this – I think my kids would love it!

      Reply
    3. Debs

      September 08, 2012 at 1:38 am

      Fabulous. I love the easy way you’ve explained it. Pinning to my science board 🙂

      Reply
      • ScienceSparks

        September 09, 2012 at 7:29 pm

        Thank you. x

        Reply
    4. JDaniel4's Mom

      September 08, 2012 at 3:00 pm

      I have treasures that would be great for this lesson.

      Reply
      • ScienceSparks

        September 09, 2012 at 7:28 pm

        do let us know if you do it. x

        Reply
    5. maggy, red ted art

      September 09, 2012 at 8:25 am

      Fantastic. Such a fascinating science experiment for kids!!! Love it.

      Reply
    6. maggy, red ted art

      September 10, 2012 at 6:29 pm

      PS thanks for sharing on Kids Get Crafty!

      Reply
    7. Carrie

      September 14, 2012 at 10:26 pm

      So cool!! I love it. Thank you for sharing on Sharing Saturday!!

      Reply
    8. Cami

      April 21, 2013 at 8:55 pm

      Another great demo for teaching density would be with pop. What you need is a fish tank full of water, a diet coke, and a regular coke. When you put the two cans in the water, the diet coke will float and the regular coke will sink. Explain to the kids that since the diet coke does not have as much mass, it is less dense so it floats.

      Reply
    9. TechyKids Canada

      August 03, 2021 at 7:58 am

      Experiments like these are prefect for making learning fun for kids. It can spark their enthusiasm towards science. Thanks for sharing this idea!

      Reply

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