1.5 - Density and pressure

Question 1

What is density?

Answer 1

Mass per unit volume (kgm-3)

Question 2

How do you measure the density of a gas? (4)

Answer 2

• The mass of the gas = (The mass of the gas + the mass of the flask) - The mass of the flask
• The gas is then evacuated
• Water enters the flask to replace the evacuated gas and the volume is measured using a measuring cylinder
• Divide the mass of the gas by the volume of the flask to calculate the density of the gas

Question 3

How much further apart are gas molecules than solid or liquid molecules?

Answer 3

10x further apart approximately

Question 4

What is pressure?

Answer 4

The force per unit area, where the force acts normal to the surface (Pa)

Question 5

What does the pressure at the point in a fluid at rest depend on? (3)

Answer 5

• The density
• The gravitational field strength
• The depth

Question 6

What is buoyancy force (upthrust)?

Answer 6

The difference in the forces at the bottom upwards and the top downwards on an object, when the bottom upwards force is greater