What Matter is Made Of 9.3 Interpreting evaporation data
Miriam is investigating evaporation. She takes a small damp tissue and places it in the garden shed. She hangs a big wet towel beside a heater. The tissue in the shed dries first. Miriam comes to the conclusion that cold conditions speed up evaporation.
1. How could Miriam improve her investigation? 2. Does the evidence support her conclusion? Why?
Condensation
Cooling a gas takes energy from its particles so they slow down and move closer together. The gas condenses to a liquid. This is called condensation.
‘Foggy’ windows
Explain why windows of a car ‘fog up’ on a cold, wet day.
z Sublimation
When some substances are heated, they do not melt but turn straight into a gas. They do not form a liquid. This is called sublimation.
For example, carbon dioxide is solid at temperatures below –78.5 °C. At this temperature and above, solid carbon dioxide changes state to become a gas. It does not normally exist as a liquid.
Solid carbon dioxide is also known as ‘dry ice’ and is often used for special effects at concerts.
