Experiment

This activity created in partnership with AGI.

Water is the only substance on our planet that occurs naturally in all three states of matter: solid (ice), liquid, and gas (water vapor). In its three states of solid, liquid and gas, water has different densities. (Density can be defined as the amount of matter in a particular volume of space, or “mass per unit volume.”)

The Earth system is made up of the lithosphere (the rocks that make up the Earth), atmosphere (air), hydrosphere (water), and biosphere (plants, animals and other living organisms). The differing densities of water in its three states have a great impact on the Earth system. For example, many ocean currents are caused by the difference in the densities of warm water and cold water. Ice forms at the top of water in a pond instead of at the bottom and icebergs float in the open sea because of density differences.

Calculating the Densities of Water and Ice

In this activity, you will investigate the density of both liquid and frozen water (ice). This activity can be done in groups of two or three students.

Tools and materials

• Transparent drinking cup or glass that can hold at least 250 mL (approximately 8.5 oz)
• Six ice cubes
• Insulated container to keep the ice cubes from melting
• Source for room temperature water and cold water
• Digital scale or balance
• 250-mL graduated cylinder or measuring cup
• Calculator (optional)
• Paper towels
• Pencil
• Notebook and pen

Note: We recommend using a graduated cylinder for best results; however, if you use a graduated cylinder, make sure your ice cubes are small enough to fit inside.

What to do

Put some room temperature water in the transparent cup. Observe what it looks like, feels like, and smells like. Write your observations in your notebook.   Discard the water in the cup. Then place a small piece of ice in the cup and observe what it looks like, feels like, and smells like. Write your observations in your notebook.   Leave the ice alone for ten minutes. When you return to the cup, observe what has happened and write those observations in your notebook.   Compare and contrast your observations of the water and the ice.
Use the balance to measure the mass of the empty graduated cylinder or measuring cup.
Fill the graduated cylinder to the 100 mL line with room temperature water. This is your volume of water in mL. Record this volume in your notebook.
Use the balance to measure the mass of the cylinder and the water sample in grams (g).
Calculate the mass of the water by subtracting the mass of the cylinder from the combined mass of the cylinder and water. Record the mass of the water in your notebook.   Calculate the density of the water in grams per milliliter (g/mL) by dividing the mass by the volume. Record your calculation.   Fill the graduated cylinder to the 200 mL line with cold water.
Measure the mass of an ice cube in grams (g). Record this mass in your notebook.
Quickly put the ice cube into the graduated cylinder. Use the blunt end of a pencil to push the ice just below the water line. Record the volume of the water and ice in the cylinder in mL.
Calculate the volume of the ice cube by subtracting the original volume of water in the cylinder (200 mL) from the volume of the water and ice. Record this number in mL.   Calculate the density of the ice in grams per milliliter by dividing the mass of the ice by the volume. Record your calculation.   Use your observations to answer the following questions: How does the density of ice compare with the density of water? How does the difference between the densities of ice and water explain your observations? How do you think the comparative densities of ice and water play a role in the Earth system?

	Digging Deeper Find out more about water and density.