Frost and dew

Summary

Make frost and dew on the outside of a can

Science content

Chemistry: States of Matter, Properties of Materials (K-7)

Chemistry: Physical Changes, Solutions, Mixtures and Separating (2, 4, 5, 6)

Earth/Space: Weather, Seasons, Climate Change (K, 1, 4, 7)

Science competencies (+ questioning + manipulation + others that are in every activity)

Questioning/predicting: predicting (1 up), hypothesizing (7)

Evaluating: inferring (3 up)

Lessons activity is in

Weather

Weather phenomena

States of Matter and State Changes

Weather and Seasons

Materials

Metal can (e.g. soup can with the label removed)
Ice to fill the can
Salt, about 2 tablespoons

Procedure

Add the ice and salt to the can.
Leave undisturbed for 15 mins.
Add more ice as it melts down.

The ice melts and starts to fill the can with water. The salt lowers the freezing point of the water, so the water can get below 0 degrees centigrade, making the bottom of the can next to the water very cold.
Frost (ice) forms on the bottom of the outside of the can where it is coldest, and dew (water) is on the top of the outside of the can (where there is no cold water on the inside).

There is always water in the air. When it is cold, what happens to the water in the air? It turns to a liquid and makes water drops (like the top of your can). See wet grass in the morning even though it has not been raining. Called dew. (Show image).
When it is really cold, what happens to the water in the air? It freezes into ice (like at the bottom of your can). This happens on the grass too - sometimes the grass is white in the morning. It is called frost. (Show image).

Note that this activity does not work so well in a very warm classroom.

Notes

Does not work in a glass nearly as well (for me).

Grades taught

Gr K

Gr 1

Gr 2

Gr 3

Gr 4

Gr 5

Gr 6

Gr 7

Activity