Topic 3: Thermal Energy Flashcards
Temperature
A measurement of average kinetic energy of the molecules in a substance. A scalar quantity. If two objects have the same temperature, there will be no net heat flow between them (they are at thermal equilibrium).
Internal energy
The energy contained in an object due to the random KE and PE of the molecules.
Thermal energy
The non-mechanical transfer of energy between a system and its surroundings.
Mole
The amount of a substance that contains the same number of particles as there are atoms in 12g of carbon-12.
Molar mass
The mass of 1 mole of a substance. eg molar mass of water is 18g
Avogadro’s constant
The number of particles in a mole. A=6.02 x 10^23
Thermal capacity
The amount of thermal energy required to raise the temperature of an object by 1K.
Specific heat capacity
The amount of thermal energy required to raise the temperature of 1kg of a substance by 1K.
Macroscopic
Considers properties of matter such as pressure, volume, temperature (not in terms of particles).
Microscopic
Considers properties of matter at a particle level. Molecules are in motion and collide with each other and the container.
Kinetic energy of particles
Temperature is a measure of the average random kinetic energy of the particles.
Evaporation
The process by which faster-moving molecules escape from the surface of a liquid. This results in a cooling of the liquid.
Boiling
The process by which a liquid changes into a gas at the constant temperature of the boiling point.
Specific latent heat
The amount of thermal energy required to change the state of 1kg of a substance without a change in temperature. SLH of fusion is solid to liquid; SLH of vaporisation is liquid to gas.
Ideal gas
One that follows the gas laws for all values of P, V and T. PV= nRT
Kinetic model of ideal gas
A model which treats a gas as many molecules subject to the following assumptions:
● The molecules obey Newton’s laws
● The intermolecular forces are negligible
● The molecules are spherical with negligible volume
● The motion of the molecules is random.
● The collisions are perfectly elastic.
● The time taken for a collision is negligible.
Phases of matter
Particles in a solid are locked into the crystal structure and do not have enough KE to escape. In a liquid, they overcome the chemical bonds but cannot separate completely for the other atoms. The particles in a gas have enough KE to escape from each other.
Thermal contact
For 2 objects, if thermal energy can be transferred as a result of temperature difference.
Thermal equilibrium
2 objects at same temperature after thermal contact
