Pressure

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- Defined as: Force per unit area

- p = F/A

- Unit = N/m² or Pa (Pascal)

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1. Pressure & Temperature of a gas

2. Pressure & Volume of a gas

1. If the temperature of a gas is increased, the average velocity of the molecules is increased, which increases momentum. Hence, the molecules will collide with the walls of the container more often and with greater force. This causes the pressure to increase.

2. If the volume of a gas is decreased, while maintaining a constant temperature, the molecules will be squashed together and will collide more often with the walls of the container. Hence, the pressure will increase - pressure and volume have an inverse relationship.

1. Thermal capacity

2. Specific heat capacity

3. Specific latent heat

1. The ability of an object to store heat energy.

- Calculated by the amount of heat energy needed to raise the temperature of an object by 1^oC

Thermal capacity = mc

2. The amount of heat energy needed to raise 1kg of a material by 1^oC.

c = E/mΔT

3. The amount of heat required to change the state of 1kg of a substance, without changing its temperature.

E = mL

Evaporation

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- Occurs when fast moving molecules escape the attractive intermolecular forces of the liquid, and become a gas

- The temperature of a liquid determines the average kinetic energy of its molecules

- Has a cooling effect

- The rate of evaporation is affected by surface area, temperature and wind

The pressure & volume of a gas have an:

a) Infinite relationship

b) Approximately proportional relationship

c) Inverse relationship

d) Hourly meeting

Answer: c)

The pressure and volume of a gas have an inverse relationship - if the volume of a gas is decreased (while maintaining a constant temperature), the pressure will increase.