Frost on Cars

Sometimes, in the morning, you may find a layer of ice on your car window. This is called frost. Sometimes the frost is very thick, and sometimes it’s thin. Sometimes the frost is just on the windows, and sometimes it’s all over the car. It may take a while to melt off, or you have to scrape it off with a handy dandy ice scraper. Frost is more common in Iowa during the winter months. However, it does not frost every night. By observing frost patterns over time, you could determine why it frosts some nights but not others.

• Why does it frost overnight some nights and not every night?

• How/why does frost occur?
• What might the mornings when there is frost and the mornings when there is no frost have in common?

Students could:

• Have students put a cup of juice in the freezer and a cup of juice in the fridge. They will see that the liquid gets cold enough to freeze in the freezer, but it is not cold enough to freeze in the fridge. This is what happens with the moisture in the air freezing on cars to create frost when the temperatures get cold enough. When the nighttime temperature is not cold enough, the liquid will not freeze (i.e. the cup of juice in the fridge), and it will just stay as dew (which can also be observed during non-frost seasons).
• Observe when it frosts and record the data (nighttime temp) on a classroom weather tracking calendar. During the warm seasons, students can observe when there is dew on the grass and the teacher can explain that if it were cold enough, this dew would freeze into frost. (This is a whole-class activity guided by the teacher)

• National Geographic | Frost:  This is a valuable website for instructors to use to brush up on their knowledge about the frost process. It describes types of frosts and effects of frost on human activities.
• PBS LearningMedia |Bringing the Universe to America's Classrooms: Earth and Space Science: Using Weather Data to Find Patterns: This GBH lesson plan introduces weather phenomena with a PEEP and the Big Wide World video and includes handouts to help students track daily weather factors at their location.