Water Boiling

Question

A student collects temperature data and makes observations of a pot of water on the stove. He observes that the water is boiling after 10 minutes.The picture shows the pot of water at 0 minutes and 10 minutes.

The table shows the temperature of the water as it is heated over 10 minutes.

Time (Minutes) Temperature (°C)
0 20
2 36
4 52
6 68
8 84
10 100
The lid on the pot shakes and steam escapes when the water boils. Which relationship explains why this happens?

A.
Molecules move faster when they are a gas compared to when they are a liquid. When the water boils, there are many fast-moving gas particles colliding with the lid.

B.
Molecules move faster when they are a liquid compared to when they are a gas. When the water boils, there are many fast-moving liquid particles colliding with the lid.

C.
Molecules move slower when they are a liquid compared to when they are a gas. When the water boils, there are many slow-moving liquid particles colliding with the lid.

D.
Molecules move slower when they are a gas compared to when they are a liquid. When the water boils, there are many slow-moving gas particles colliding with the lid.

Answer 1

The correct choice that explains why the lid shakes and steam escapes when the water boils is:

A. Molecules move faster when they are a gas compared to when they are a liquid. When the water boils, there are many fast-moving gas particles colliding with the lid.

When water reaches its boiling point (100 °C at sea level), it changes from a liquid to a gas (steam). The gas molecules move much faster than the liquid molecules, and as they escape from the boiling water, they create pressure that can cause the lid to shake.