Density (1B) Online Lab Instructions and Pictures Assignment: Download the lab file (Density Lab 1B) from the labs webpage. Then, use the instructions and pictures in this file to complete the lab. For some activities, you will need to watch short videos of experiments on the labs webpage. For more information on completing labs at home online, see the instructions for doing labs at home online in the syllabus. Go to the next page to begin the lab.

Activity 1: Density, Floating, and Sinking

Calculate the Density of Wood: Mass of the Piece of Wood

Remember: A Penny has a mass of 2.5 grams.

Grams (g)

Calculate the Density of Wood: Size (Volume) of the Piece of Wood

Calculate the Density of a Penny: Size (Volume) of a Penny

Centimeters (cm)

Which sinks, the penny or the wood? Which floats? Which is heavier? Which is lighter? Which has a higher density? Which has a lower density?

Activity 2: More Density, Floating, and Sinking

How many pennies does it take to make the white cylinder sink?

Watch the video to see what happens! Use the pictures below to calculate the size of the cylinder. Then, use the volume of the cylinder and the weight of pennies (2.5 grams each) + the cylinder (5 grams) to calculate the combined density of the pennies + the cylinder in each experiment.

Activity 3: The Cartesian Diver

The floating eyedropper is called a “Cartesian1 Diver.”

Notice the bubble inside the eyedropper.

What happens to the bubble when I squeeze the plastic bottle? In other words, does the bubble become larger or smaller?

1 This experiment is attributed to Rene Descartes, a Belgian soldier, mathematician, philosopher, and scientist of the Renaissance. Take a moment to imagine French aristocrats sitting in their salons (like in costume dramas) marveling over this device.

Eyedropper

Bubble Bubble

What does the Cartesian Diver (the eyedropper) do if I squeeze hard enough?

Watch the video to see what happens!

Why does it do this?

(Hint: Discuss density. How have the mass and/or volume of the eyedropper and bubble changed? How will it affect their density?)

Activity 4: Thermal Expansion and Contraction

What happens to the level of the red liquid when I put it in the pot? What happens to the level of the red liquid when I take it out of the pot?

Watch the videos to see what happens!

Carefully watch the level of the red liquid in the videos.

The pictures below show the possible changes to the size of the bottle and the level of the red liquid. The black dashed line represents the original size of the bottle at room-temperature.

In the Beginning

A B C

D E F

Activity 5: Density, Temperature, and Salinity

Does the warm, red water sink or in room-temperature, fresh water? Does the cold, blue water sink or in room-temperature, fresh water? Does the salty, green water sink or float in room-temperature, fresh water?

Watch the videos to see what happens!

Activity 6: Density and the Buoyancy Force

If you do not know whether oil floats on water or water floats on oil, try the experiment for yourself in your kitchen. Any kind of cooking oil (corn oil, canola oil, peanut oil, etc.) is fine. Fill a glass with water and just pour a little oil into the glass and watch what happens.

In which fluid does the hydrometer float higher out of the water? (Hint: Look at how much of the straw is out-of-the-water.) In other words, which fluid pushes up on it harder (gives it more support)?

Oil Water

Hydrometer

Straw out- of-the-water

Straw out- of-the-water

Do eggs float in fresh water or salty water? In other words, which fluid pushes up on it harder? gives it more support?