## The Tip of the Iceberg

### Overview

Children ages 8 to 13 observe an ice cube in water and — literally — draw conclusions about properties of ice based on their observations!

### What's the Point?

• Ice is a unique substance because its solid state — ice — is less dense than its liquid state. Because of this property, ice floats in water.
• Physical properties are characteristics of a substance. They do not change. Physical properties include color, smell, freezing/melting point, and density.
• Density is a measure of the mass per unit volume of a substance.

### Materials

For each child:

For each group of three to four children:

• 1 clear pitcher (or other container) that is at least twice as tall as, and several times the volume of, the ice the children created in the Amazing Expanding Ice activity
• Water to fill ¾ of the container
• Ice from the Amazing Expanding Ice activity
• Non-permanent marker
• Paper towels

For the facilitator:

### Preparation

• Fill containers ¾ full with water

### Activity

1. Introduce the activity by revisiting what the children have learned so far about the properties of ice. Use this opportunity to review and reinforce the concept of properties, and convey to the children that properties can also include the way a substance behaves.
• What are some of the properties of ice? Answers will vary, but may include its color, how it feels, its temperature, etc.
• Can they name some of the properties of ice they learned about in The Amazing Expanding Ice experiment? What they learned should include that ice is less dense than water and water expands as it freezes.
2. Distribute the containers of water, paper towels, and the Ice Investigator Journals. Ask each team to move their container to a location where it can be viewed by the whole team. Have the children mark the water level on the sides of their containers and draw their water levels in their journals.
3. Distribute one of the cups of ice from the Amazing Expanding Ice activity to each group. Share that they will be placing the ice into the container of water.

• What do they think will happen?
4. Invite the groups to carefully place their ice in their container.
• What is the ice doing? The ice is floating.
• What happened to the water level? It went up.
• What happens to the water level if the children push the ice down into the water so that the top of the ice is just under the water surface? The water level goes up even more!
The fact that the solid form of water floats in water is one of the special properties of water. It's solid form — ice — is less dense than its liquid form. So ice floats in liquid water!
5. Ask them to view the ice through the side of the container.
• Is the whole ice cube above the water? No, most of the ice cube is underwater.
• About how much of the ice is above thewater line - 1/4, 1/2, 3/4, more? Actually, about 10%, or 1/10, of the ice will be above, and 90%, or 9/10, will be below the water line.
• What does the fact that ice floats tell you about its density? Is it more or less dense than the water that surrounds it? Ice is less dense than water, which is why it floats!
Facilitator's Note: Density is mass per unit volume, or the ratio of the amount of matter in an object compared to its volume, or simply put:
• Mass = the amount of "stuff"
• Weight = how heavy the "stuff" is (Weight is determined by the amount of gravitational pull on an object, which is a property of the mass of the planet the “stuff” is on. The greater the gravitational pull, the more the "stuff" weighs.)
• Density = how tightly packed the "stuff" is
• Volume = the area of space the "stuff" takes up
If we apply this information to the cups, the cup of water and the cup of ice have the same mass, i.e. amount of "stuff." Because they had the same amount of "stuff," they have the same weight.

The "stuff" (molecules) in water is more tightly packed than in ice, so water has greater density than ice. Don't let the fact that ice is a solid fool you!

As water freezes it expands. So, ice has more volume (it takes up more space, but has less density) than water.
Have the children annotate their findings in their Ice Investigator Journals.
6. Based on what they have observed about small ice chunks, invite the children to apply what they have learned to make a prediction about large ice chunks, otherwise known as icebergs! Ask them to indicate in their Ice Investigator Journals what the whole iceberg, above and below the water, might look like.
• Did they use their findings from their experiment to place about 1/10 of the iceberg above and 9/10 below?
• Do they think all ice that is made of water — big and small— floats in water? Yes! Ice cubes float in glasses of water and icebergs float in the sea.
Facilitator's Note: Water is the only known non-metallic substance that expands when it freezes; its density decreases and it expands approximately 9% by volume. This decreased density allows the solid form of water to float on the liquid form. Icebergs float on the ocean with only about 10% of their mass appearing above the ocean; the remaining 90% is concealed beneath the waves.

### Conclusion

If the children have started to construct a snow mobile, invite them to record any answers they discovered on the appropriate pieces. Some of the questions that they can answer might include:

• When water turns to ice, it expands / contracts. (circle one)
• Water is more dense / less dense than ice. (circle one)
• Ice will float/sink in water. (circle one)

Have them annotate any new questions they have or interesting things they learned on the appropriate shapes of either raindrop, cloud, or snowflake.