Is there a way to “see” the density of liquids? You bet! It all depends on density.
Density is the mass of a substance per unit volume (how much space it takes up). You can determine density by dividing the mass by the volume – D=m/v.
The volume is based on the space something takes up, how it fills a container (for liquids). Mass is dependent on atoms. Specifically, what’s the mass of the atoms, how tightly are they spaced, and what’s their size?
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So, back to our original question. How can we see the density of liquids? Let’s experiment.
- Quart canning jar (or a similar sized container)
- Measuring cup(s)
- 6 ounces of honey, water, vegetable oil, and rubbing alcohol
- Food coloring
- A handful of small objects (we used a ping pong ball, LEGO piece, peanut M&M, raisin, marble, and a piece of a tea light candle)
What do you think will happen when you add all of these liquids to the same container?
Think about the liquids you’re using and how their densities compare to each other. On your sheet, order them according to what you think their density is.
If you have a kitchen scale, measure the mass of each liquid before you add it to the jar to see if your hypothesis was correct. Don’t forget to log it on your sheet.
- Measure out 6 ounces of honey. Without touching the sides, pour it into the jar. Feel free to use a funnel if you’d like.
- Measure out 6 ounces of water. Add a few drops of food coloring and mix well. I would recommend a dark color like blue, red or green. Slowly pour the water into the center of the jar.
- Measure out 6 ounces of vegetable oil. Slowly pour the water into the center of the jar.
- Measure out 6 ounces of rubbing alcohol. Slowly pour the water into the center of the jar.
Are your liquids stacked on top of each other? Pretty cool, huh?
So, why did it happen? Why do the liquids separate when they’re in the same container instead of having them all combine into one solution? What does it say about each liquid’s density? Make sure to write down your answers.
What about the density of solids compared to the liquids?
It’s time to test the density of solids and how they compare to the liquids.
First, write down what you think will happen when you add the small objects to the jar. What layer do you think each object will end up in?
Next, carefully drop each object, one at a time, into the jar. Give them a few minutes to settle and then record your findings.
Our kids had a blast discovering new things about solids and liquids during our co-op class.