Unit 5 - Thermal Physics

Thermal energy definition

Thermal Energy of an object refers to the energy stored as Kinetic Energy due to their random motion.

Heat definition

Heat is the transfer of thermal energy between systems due to a temperature gradient. It always flows spontaneously from a region of higher temperature to a region of lower temperature until thermal equilibrium is reached. Measured in joules

Temperature definition

A measure of average kinetic energy of the particles in a substance. It is measured in celsius or kelvin. The higher the temperature, the faster the particles move

celsius definition

Temperature scale based on the freezing and boiling points of water. 0°C freezing point, 100°C boiling point.

kelvin

the kelvin scale is the SI unit of temperature and used in science and engineering. It starts at absolute zero, the coldest possible temperature where all particle motion stops.

kelvin formula

K = °C + 273

what is 0 kelvin

-273 °C

Internal energy

Internal energy is the total energy of a system due to teh kinetic energy of its particles and the potential energy due to intermolecular forces

How is energy sometime wasted?

In an energy transfer system, some energy is wasted as heat due to inefficiences. this energy is dissipated into surroundings.

3 types of thermal energy transfer

conduction, convection, radiation

Conduction

Transfer of the heat through direct contact between particles of a material without the overall movement of the materials. it occurs when there is a temperature difference within solids. the heat flows from a region of high temperature to a region of low temperature.

convection

Transfer of heat through teh movement of fluids. this is due to the convection current. It occurs when warmer particles gain energy, expands, becomes less dense and rises while cooler fluids contract necome denser and sinks creating circulation.

radiation definition

transfer of heat through electromagnetic waves without the need for a medium.

Specific heat capacity

specific heat capacity is the amount of heat energy required to raise the temperature of 1kg of a substance by 1°C. unit: J/kg °C

formula for specific heat capacity

Q = m c T

solid description

solid: fixed shape/volume. tightly packed in a regular pattern. strong intermolecular forces. particles vibrates but cannot move freely, hence doesn’t flow and is not compressable

liquid description

liquid: fixed volume but shape of container, particles are close together but slides on top of one another due to weak intermolecular forces.

gas

no fixed shape or volume. very weak basically negligible intermolecular forces, highly compressible, flows easily.

plasma

ionized gas with extremely high energy. it has free moving electrons and a positively charged nuclei. it conducts electricity and generates magnetic fields,

latent heat definition

latent heat is the amount of energy required to change the phase of 1kg of a material without changing temperatures.

formula of specific latent heat

Q = mL

fusion latent heat

amount of energy needed to change 1kg of a substance from solid to liquid without changing its temperature

latent heat of vaporization

amount fo energy needed to change 1kg of a substance from liquid to gas without a change in temperature

evaporation definition

Evaporation is the process where particles at the surface of a liquid gains enough kinetic energy to overcome intermolecular forces and change into a gas. It happens at any temperature below the boiling point and at the surface.

boiling definition

Boiling is the rapid change of phase from liquid to gas that occurs throughout the entire liquid. It bubbles from within the liquid and only occurs when the boiling point is reached at which all particles have gained enough kinetic energy to overcome intermolecular forces.