A study of density explores how closely packed molecules are in an object or a liquid. A liquid is compared to whether it is heavier or lighter than water – if put in the same cup as water, will it sink to the bottom of the cup or float on top of the water. In the first experiment, you compare the weight, or density, of five fluids.
Density Lasagna Experiment
You will need
- A tall drinking glass
- A measuring cup
- Pure maple syrup
- Glycerol (found in pharmacies)
- Water
- Cooking oil
- Rubbing alcohol
- Food coloring
Procedure:
- Set the drinking glass on a table or counter. Select a spot where you can leave the experiment for a couple of days without having to move it.
- Pour ¼ cup of maple syrup into the glass.
- Slowly pour ¼ cup of glycerol into the glass. Avoid mixing the two fluids. Notice how the glycerol sits on top of the maple syrup.
- Add a drop of blue food coloring to ¼ cup of water. Gently pour into the glass so not to disturb the layered liquids.
- Pour ¼ cup of cooking oil into the glass.
- Add a drop of red food coloring to ¼ cup of rubbing alcohol. Pour into the glass.
- Avoid moving the glass. Observe the results. Do the liquids mix after an hour or a day?
Liquid Lava Science Experiment
You will need
- A tall drinking glass
- Water
- Food coloring
- Vegetable oil
- Salt
Procedure:
- Fill the glass with three inches of water.
- Add one drop of red food coloring.
- Slowly pour in one-third cup of vegetable oil so it settles on top of the water.
- Sprinkle salt into the glass until a glob of oil sinks to the bottom of the glass.
- Wait. Within a minute or so, the oil will float to the top of the water.
- If you’d like, add more salt until the oil sinks again.
Explanation of Density
As you saw in Density Lasagna, the liquids remain separated. This is because each fluid was lighter than the liquid below it. Another way to think of it is that the liquid with the molecules that are further apart is lighter than the liquid with the molecules that are closely packed.
If you tried the experiment again and poured the fluids into the glass in a different order, the liquids would mix as the heavier liquids sank.
In Liquid Lava, the oil floated on the water because it is less dense than the water. However, when you added the salt, the salt clung to the oil and dragged it to the bottom of the glass. It couldn’t stay at the bottom because salt dissolves in water, thereby causing the oil to float back to the top.
After exploring the density of the liquids in these experiments, discover the density of some of the other liquids in your home. To get a better sense of how those liquids compare to the ones in the experiments, create a chart, listing each fluid between the liquid it was lighter than and heavier than.
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