Making A Comet

Age

Elementary School, Middle School, High School

Format

Hands-on

Materials

   Water
   Soil
   Soy sauce
   Ammonia
   Dry ice
   Small blast shield
   Box with plastic lining that can be used to compress mixture
   Gloves
   Safety glasses
   Demonstration display poster board
   Hot plate 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience. Dry ice is very, very cold! Don’t allow the kids to touch it! Be sure to always wear gloves and safety glasses during the demo. Keep the kids behind the small blast shield!

Preparation

Set up blast shield to keep kids from getting their hands into the dry ice.

Demonstration

The demonstrator will mix together the ingredients that represent the components of a comet, being careful not to hurt themselves or anyone else with the dry ice. Once the ingredients are mixed the demonstrator then compresses the mix together to form a sort of ball.

What to Say

Start by asking if anyone has seen a comet. Show the pictures of various comets on the display board and point out the various features: nucleus, coma, dust tail and plasma tail. Point out in the diagram of the comet orbiting the sun that the tail is always pointing AWAY from the sun. Ask if any of the kids can explain why that is. Likely no one will know why so explain that this demo will help illustrate why that is and what comets are like in general.

Mix the ingredients together and describe what each ingredient represents. The water will represent (once frozen) the ice found in comets, the soil represents the dark organic material, the soy sauce represents the other complex chemicals found in comets, the dry ice represents the frozen carbon dioxide locked into comets and the ammonia is the same as the ammonia found in comets.

After the ingredients have been pressed into a sort of ball, show the comet to the kids and explain that it is similar to the nucleus of a comet.

Use a hot plate to demonstrate the effect of the sun on the “comet”. It should start to evaporate more quickly and create more of a coma. Explain that the sun is really really hot and when a comet gets close to it, it starts to heat up and evaporate. This stuff that's evaporating away is what makes the long tail that you see in pictures.

Why It Is

When the “comet” heats up, it sublimates into a gas and brings some of the stuff that's mixed in with it creating a coma, which if it were moving would be able to form a tail.

Real Life Examples

Real life comets are an example.