How to Explain Density to Elementary Students

••• Bubbers13/iStock/GettyImages

An explanation of density to elementary-school children can begin with discussion on weight, especially why two objects of the same size might have different weights. Next, introduce the concept of volume to describe the size of objects. Third, you can show them why some objects sink in water and others float, laying the foundation for the understanding of density.

    Begin by holding up both balls.
    ••• Fuse/Fuse/Getty Images

    Hold up the Styrofoam ball and the rubber ball and ask the class to guess which ball would be lighter. Allow a student or two (or the entire group, for small classes) feel each of the balls for themselves. Explain that the Styrofoam ball has less mass once they've understood that it's lighter.

    Turn on the scale.
    ••• Les Howard/iStock/Getty Images

    Turn on the scale and show the class that it sets to zero when turned on and empty. Set a light object, such as car keys, on the scale and point to the numbers as they rise. Set a heavy object, such as a book, on the scale to show that the numbers climb much higher for heavier objects. Remove the book and let the scale return to zero.

    Ask the kids to read the numbers on the scale for both balls.
    ••• DAJ/amana images/Getty Images

    Place the Styrofoam ball on the scale and tell a child to read the numbers on the scale. Remove the Styrofoam and place the rubber ball on the scale. Tell the same child to read the numbers on the scale. Ask the children whether the second ball had a higher or lower number.

    Blow up two balloons.
    ••• Jezperklauzen/iStock/Getty Images

    Cover the basic introduction to volume again. Blow up two balloons, making them of noticeably different sizes. Ask the class which balloon takes up more space. Explain that the larger balloon takes up more space and, therefore, has a higher volume.

    Set out three containers and fill them to different levels.
    ••• laura_uadjet/iStock/Getty Images

    Remind the class of your definition of density. Set out the three small plastic containers. Leave the first container empty. Pour a small amount of water into the second container and a large amount of water into the third. Explain that the containers have the same volume but ask which of the three will float in a large tub of water. Let the children guess, examining the weight of the containers with their hands, and weigh the containers on the scale to help them guess.

    Ask the children which container they think is most likely to float.
    ••• Fuse/Fuse/Getty Images

    Place the container the children choose as the most likely to float in a large plastic tub filled with water. Follow with the other two containers. Explain why each container floated or sank, based on its weight relative to the water.

    Wrap up the experiment by explaining to the children that a change in volume or mass changes density.
    ••• monkeybusinessimages/iStock/Getty Images

    Wrap up your experiment by explaining to the children that a change in volume or mass will change the total density of an object. Answer any questions they might have for you, then clean up your workstation, allowing the children to help if time permits.

    Things You'll Need

    • Styrofoam ball
    • Rubber ball, similar physical size to Styrofoam ball
    • Electronic scale
    • Balloons
    • 3 small plastic containers
    • Water
    • Plastic tub

Related Articles

2nd Grade Water Density Projects
Density Experiments for Elementary
Kindergarten Activities for Volume
How to Teach Buoyancy to Grade School Children
Easy Ways to Show Mass Vs. Density for Kids
Fun Archimedes Principle Experiments
How to Measure Mass & Density
Newton's Laws of Motion for Kids
How to Explain Density
Easy Homemade Weather Instruments for Kids
How to Calculate a Quintile
How to Explain Phases of the Moon & Tides to Children
Activities for Rational Counting for Preschool
Fun Outdoor Math Activities
How To Play Math Bingo
Simple Science Fair Projects for 6th Graders
How to Make a Model of the Solar System for the Fifth...
Science Transportation Activities for Preschoolers
Science for Kids: What Are the 3 States of Matter?
What Is Low Density?