Explore! Ice Worlds!

Ice and Seek: What is Ice?


In this two-part, 60-minute activity, children, ages 8 to 13 begin exploration of ice on planets and moons in our solar system by building an understanding that there are different types of ices. As teams, the children examine three types of ice — dry ice, alcohol ice, and water ice. They identify the ices based on clues then match the type of ice to the appropriate planet or moon on which it occurs.

What's the Point?

  • Different substances "freeze" — become solid — at very different temperatures. For example, the freezing point of water (H2O) is 0°F (32°C), the temperature at which carbon dioxide (CO2) forms dry ice is –78°F (–109°C), and liquid iron becomes a solid at 1535°C (2795°F)!
  • In addition to water ice, there are other ices in our solar system on the surfaces of planets and moons, and forming comets.
  • "Ice" is a term used by planetary scientists to refer to substances that are common liquids (or gases) under Earth's surface conditions, but occur as solids — frozen — in other places in our solar system. Examples are ammonia ice and carbon dioxide or dry ice.
  • The amount and type of ice on a planet or moon reveals clues to the processes happening on that planet or moon.
  • Some substances, such as carbon dioxide, can change phase directly from a solid to a gas (sublimation).


For each child:

For each team of three to four children:

  • 3 (6– 8 ounce) clear plastic cups
  • 3 ounces isopropyl alcohol
  • 9 ounces water
  • Small piece (~ 2" x 4" x 2") of dry ice (frozen CO2) from a local grocery store or wedding supply
  • Access to a freezer
  • 1 metal spoon
  • 1 thermometer
  • 1 magnifying glass
  • 1 cardboard plate
  • 1 set of small gloves (for example, garden gloves — not rubber or latex)
  • 1 Ice and Seek Packet which includes the "Instructions", "Team Observations," and "Ice Characteristics" sheets
  • Images of ice on earth and other planets

For the group:

  • 5 to 10 sheets colorful poster board
  • Planetary Ice Data Set
  • Glue or tape
  • Scissors
  • Additional images of planets and moons (optional)

For the facilitator:


  • It is important to have a responsible older child or adult at each station, especially with younger children, to ensure proper handling of the ice. The children should NEVER taste the ice and NEVER touch it without gloves.
  • Create the number of stations needed, based on the number of children participating.
  • At least a day in advance prepare the ices:
    • Fill one cup per group with a mixture of ½ water and ½ alcohol; label cups with the number "1".
    • Fill one cup per group with water; label cups with the number "2".
    • Freeze these containers
  • Dry ice can be purchased the day before; wrap it tightly in newspaper and place it in a freezer. Some will sublimate overnight, so consider purchasing a little extra. Handle the dry ice carefully, as it is cold enough to cause frostbite to exposed skin.
  • Create the posters using the planetary ice data set. Cut out and glue the information about one or two of the planets on each of the poster boards. Decorate with additional images of the planets or other craft items. Hang the posters around the room.
  • At each ice station, place a plate, metal spoon, thermometer, magnifying glass, set of gloves, and one Ice and Seek Packet.
  • Immediately prior to the experiment, place at each station a piece of dry ice on a plate and label with the number "3". Place one of the cups of water ice and one of the cups of alcohol ice at each station.


1. Prompt a discussion about ice. The children may refer to the snow mobile they created in States of Water.

  • What is ice? The children will probably refer to the ice with which they are most familiar, frozen water.
  • What are some of the properties of frozen water ice? Hard, cold, shiny.
  • Can they think of any other types of ice that are familiar to them? Most will have made popsicles from frozen juice and/or have seen frozen CO2, or dry ice.
  • What makes "ice" ice? The children may have many ideas, including that freezing a liquid makes ice.
  • Ask the children to recall the three states of matter that we commonly encounter. Gas, liquid, and solid.
  • Which state is ice? Ice is a solid.

Share with the children that there are lots of substances around us that are solid, but we do not call them ice. We say that windows are made of solid glass (or glass) but we don't say they are made of glass ice. Metal scissors or staplers are made of solid metal, not metal ice. Scientists who study planets use the special term "ice" to refer to substances that usually are liquid (or gas) on Earth, but that form solids on other planets or moons or in comets. On Earth, carbon dioxide typically is a gas and ammonia is a liquid. On some planets there is no water ice, but there is lots of dry ice!  Other planets have ammonia ice.

2. Distribute — or display — the images of ice on earth. Ask the children to examine the images.

  • What do they see? Is there ice (or snow) in the different images? Yes.
  • How would they describe the ice? The children may say it is white, it is covering land or water, some looks smooth, some looks rough, etc.
  • Can liquids other than water make ice? Yes.
  • Can they name any other liquids that could freeze?
  • If liquids other than water can freeze, might there be other types of ice than "water ice?" Yes!

3. Share the images of ice on other planets. Have the children carefully observe the images.

  • What do they see in the images?
  • Is there ice or snow in any of the images?
  • Do they think the ice they see is the same type of ice we have on Earth? Accept all answers.

4. Divide the children into teams of 3–4 and explain that each team will examine different types of ice that occur on other places in our solar system. Based on clues they will receive, their mission is to discover the identities of these ices.

5. Have the children examine the Ice and Seek "Instructions", "Team Observations", and "Ice Characteristics" Sheet. The Ice and Seek Team Observations sheet will help the children make their observations of the different ices. Based on their observations, the children will work in teams to identify the different types of ice using the "Ice Characteristics" sheet.

6. Review with the children how they should conduct their investigation. Reinforce the importance of proper handling of the ices! Dry ice can cause frostbite. Do encourage them, however, to use the tools at each station. At each station they should:

  • Record the ice sample number on their Team Observations sheet.
  • Carefully examine the ice using the tools provided at the station.
    What temperature is the ice? They should use the thermometer to take the temperature of the ices. When testing the temperature of the dry ice, they should lay the thermometer on the block of ice, but do not touch the ice itself. For the alcohol ice, they should insert the thermometer into the ice. Note that the temperatures the children collect will be warmer than the temperatures of the ice; the air temperature in the room that is in contact with the thermometer will tend to cause a warmer reading.

    How hard is the ice? They should use the metal spoon to test for hardness by scraping and/or poking the ices.

    Does the ice cold affect metal? They should press the metal spoon on the ice and observe what — if anything — happens. Gas is trapped between the metal and dry ice. Sublimating ice "squeaks" between the cracks and causes the metal to vibrate.

    What other tools can they use to examine the ice? Remind the children to use their eyes and noses. Their senses are some of the most important tools they, as scientists, have!
  • Remind them to record their observations on the Ice and Seek "Team Observations" sheet.
  • After recording their observations, they should review the "Ice Characteristics" sheet as a team and discuss which ice they think they observed at each station. They should record their answers under "Predictions" on the Ice and Seek "Team Observations" sheet.

7. After all the teams have examined the ices and completed their Ice and Seek "Team Observations", gather the large group together and allow the teams to share their answers. Discuss what they have learned.

  • Are there different types of ices? Yes!
  • Do different types of ice have different properties? Yes.
  • Can they name some of the properties unique to the different ices? The answers may include that the ammonia ice had a strong odor, the alcohol ice was slushy and colder than the water ice, the dry ice looked like it was smoking instead of melting, etc.
  • Now they know that liquids such as water and ammonia can freeze, but do they think a gas could possibly freeze? Accept all answers.

8. Discuss their observations of the different ices. Ask the children if they noticed what looked like smoke coming from the dry ice. Explain that dry ice is actually frozen carbon dioxide (CO2). Carbon dioxide is a very common gas. It is what we exhale when we breathe and what plants need to survive. When a substance changes directly from a solid like dry ice into a gas, we call the process sublimation. Dry ice, under Earth's normal surface conditions, does not melt into a liquid, it sublimates — or turns directly into a gas. What looked like smoke was really cold carbon dioxide gas sublimating from the ice. Water ice can do the same thing; in very cold conditions, like those in Antarctica, water ice can sublimate — turn directly into water vapor.

Ask the children if they noticed that the alcohol ice was a little slushier than the water ice. Have them reflect on what they learned in The Melting Point activity about the various freezing and melting points of different substances. Share that alcohol has a lower freezing point than water, so the temperature has to be colder before it will freeze. Water freezes at 32—F (0°C). The freezing point of alcohol depends on the type of alcohol being used, but it must be much colder than water to freeze. Explain that you were able to get these samples to freeze by mixing them with water to bring their freezing points up a bit. But, even so, the alcohol could not be frozen solid.

9. After discussing the types of ices, distribute an "Ice Across the Solar System?" sheet to each child. Call the children's attention to the wall where you have placed the planetary ice data set sheets. Explain that these are images of planets, moons, and icy bodies — like comets — in our solar system. Each image on the wall includes information about the presence — or lack — of ice on that body along with the type of ice. Based on the information found on the planetary ice data sheets, their mission will be to identify, as a team, which planets and moons have ice and what type of ice it is.

10. Play Ice and Seek! Invite the teams to take their "Ice Across the Solar System?" sheets and begin their investigations! Explain to the children that they should travel as a team to each image, read the information about that planet, moon, or comet, then record on their sheets whether that planetary body has ice and, if so, where and what type of ice it is. Not all of the planetary bodies have ice, and some may have more than one type of ice in more than one place!


11. After all the teams have examined the ices and each child has completed his or her "Ice Across the Solar System" sheet, gather the group together and discuss what they have learned.

  • What are some of the properties of dry ice? It is very cold and it sublimates directly from a solid to a gas.
  • What type of ice is found on Earth? Water ice.
  • Did any of the planetary bodies have more than one type of ice? Yes. Different comets had different types of ices.
  • Were they surprised to find that comets were made of ice? Comets are made almost entirely of water ice and are often called "dirty ice balls" — or "icy dirtballs!"
  • Did any planetary body not have ice at all? If not, why not? Venus does not have ice. It has a dense carbon dioxide atmosphere that holds in temperatures of over 800°F (400°C) across the planet!
  • How do we know that ice exists on planets and moons that are so many millions of miles away?

Tell the children that in the next activity, they will learn how scientists have discovered ice in very faraway places… as far away as the edge of our solar system.

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