A rigid steel cylinder containing medical oxygen is moved from a cold storage facility into a warm hospital ward. A technician observes that the pressure reading on the cylinder's regulator increases.

Explain, in terms of gas particles, why the pressure inside the cylinder has increased.

A student writes down a simple model of atmospheric pressure:

• The atmosphere is a layer of gas held around the Earth by gravity.
• The density of the air increases at higher altitudes.
• The pressure at any point is caused by the weight of the air above it.

The student has made one mistake in this model.

Identify the wrong word and write the correct word to replace it.

Wrong word:

Correct word: