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Density is how close together the molecules of a substance are or how much mass a substance has in a given space. If you have one cup of jelly beans and one cup of marshmallows…the jelly beans have more mass…there is more “stuff” compacted into the cup. The marshmallows are mostly air. If you put each of those cups in a microwave to melt…the sugar and water that makes up the jelly beans would almost fill the cup to the top. The sugar and water that makes up the marshmallows would only fill the cup a little bit because marshmallows have less mass, they are mostly made of air. Materials with more density weigh more. A cup of jelly beans weighs more than a cup of marshmallows.
If you pour two substances of different density in a pan, the material with more density is heavier and will sink to the bottom. Watch this happen be using oil, water and food coloring to make marbled paper.
What You Need:
- Shallow Pan (like a brownie pan)
- Food Coloring
- Cooking Oil
- White Paper
You need one cup for each color of food coloring you have. Put a tablespoon of cooking oil in each cup. Add a couple drops of food coloring to each cup – one color in each cup. Stir each oil/food coloring mixture really good with a fork.
Now fill the shallow pan about half way with water. Take each cup and pour a little of the oil/food coloring mixture into the water. Put each color in a different section of the pan. Swirl the colors with a fork. When you like the pattern, lay a clean white sheet of paper on top of the water. Leave it for 30 seconds and then carefully lift it off and lay it down to dry. Pretty!
Water has more density than oil. Materials with more density weigh more. Any substance that has less density than water will float. The food coloring doesn’t mix with the water, it just floats with the oil and makes swirl patterns.
- Nye Labs: Marvelous Marbling 
- ZOOM Science Rocks: Color Splash 
- Art Smarts 4 Kids: Paper Marbling  & Create Your Own Marbled Paper 
- Bright Hub: Paper Marbling Science Project 
- PBS Kids Fetch: Potion Commotion 
- ZOOM Activity: Water Density 
- Virtual Mass, Volume and Density Lab 
More IndyPL Experiments about Density:
Words to Know:
Density – How closely packed together the molecules of a substance are.
Mass – How much matter fits in a given space.
Matter – Stuff
Weight – A measure of the force of gravity on an object. Materials with more density weigh more.
Volume – How much space a substance takes up.
*****The confusing relationship between weight and mass: On earth, a bowling ball can weigh about 10 pounds. If you take that same bowling ball to the moon it will weigh much less because the graviational pull of the moon is less than the gravitational pull on the earth. Weight is a measure of gravitational pull. So the weight of the bowling ball, or anything else, changes depending on where you weigh it. The mass of the bowling bowl does not change no matter where it is. The bowling ball has the same amount of mass on earth as it does on the moon or anywhere else you take it.