States of Matter

Question 1

What causes pressure in a gas?

Answer 1

• Collisions between gas particles and the walls of the container it is in
• Each collision exerts a force on an area of a wall; since pressure = force/area, pressure is created

Question 2

What are the assumptions made when modelling an ideal gas?

Answer 2

• The gas particles, behaving as rigid spheres, have no volume
• There are no intermolecular forces of attraction between particles
• The gas particles are in constant motion in straight lines
• Collisions between particles and the walls of the container and between individual particles are perfectly elastic (no loss of energy)
• The temperature of the gas is directly proportional to the kinetic energy of its particles and its volume
• The pressure of the gas is inversely proportional to its volume

Question 3

At what conditions (temperature and pressure) is the ideal gas theory most accurate?

Answer 3

• High temperature and low pressure
• This is because at these conditions, the particles are spaced apart, so assumptions about particle volume and intermolecular forces hold

Question 4

What is the ideal gas equation?

As is suggested by the name, this equation is only accurate when assuming gases are ideal

Answer 4

• pV = nRT
• Pressure (Pa) x volume (m³) = number of moles x gas constant x temperature (in kelvin)

• All of the values refer directly to the conditions of the gas itself
• Using the correct units is essential
• 0 kelvin is -273.15 Celsius

Question 5

What is the gas constant?

Answer 5

8.31

Question 6

Why isn’t anything from 4.2 in this deck?

Answer 6

It’s all GCSE content and this is an A Level class