Thermal Physics

What are the distinguishing properties of a solid?

Fixed shape and volume; cannot be compressed.

What are the distinguishing properties of a liquid?

Fixed volume; takes the shape of the container; cannot be compressed.

What are the distinguishing properties of a gas?

No fixed shape or volume; fills the container; can be compressed.

What is melting?

The process where a solid becomes a liquid.

What is freezing?

The process where a liquid becomes a solid.

What is boiling/evaporation?

The process where a liquid becomes a gas.

What is condensation?

The process where a gas becomes a liquid.

What is sublimation?

The process where a solid becomes a gas directly.

What is the particle arrangement in solids?

Particles are close together in a regular arrangement and vibrate about fixed positions.

What is the particle arrangement in liquids?

Particles are close together in a random arrangement and move around each other.

What is the particle arrangement in gases?

Particles are far apart in a random arrangement and move rapidly in all directions.

What happens to temperature and kinetic energy as temperature increases?

Temperature increases cause average kinetic energy of particles to increase, resulting in faster movement.

What is absolute zero?

The temperature of -273°C (0 K) where particles have minimum possible kinetic energy.

What causes gas pressure?

Gas pressure is caused by particles colliding with and exerting force on the walls of their container.

How do more frequent or harder collisions affect gas pressure?

They lead to higher pressure.

What is Brownian motion?

The random, jerky motion of microscopic smoke particles in air due to collisions with air molecules.

How is pressure defined in terms of force?

Pressure is the force per unit area exerted by colliding particles, expressed as p = F/A.

What distinguishes Brownian motion?

It involves microscopic particles being moved by collisions with atoms or molecules.

What happens to gas pressure when the volume increases at constant temperature?

Pressure decreases due to fewer collisions with walls.

What is Boyle's Law?

For a fixed mass of gas at constant temperature, pV = constant.

What does the graphical representation of Boyle's Law look like?

A plot of pressure (p) versus volume (1/V) is a straight line through the origin.

What is thermal expansion?

The tendency of substances to expand when heated.

Which state of matter expands the least when heated?

Solids.

Which state of matter expands the most when heated?

Gases.

What is the consequence of not accounting for thermal expansion?

Expansion can cause damage, such as buckling railway tracks.

How do particles behave when heated?

They gain kinetic energy, vibrate/move more, and take up more space.

What is specific heat capacity?

The energy required to raise the temperature of 1 kg of a substance by 1 °C.

What is the equation for calculating specific heat capacity?

ΔE = m c Δθ, where ΔE is the change in thermal energy.

What does internal energy refer to?

The total kinetic and potential energy of an object.

How do energy inputs during melting affect temperature?

Energy is used to overcome intermolecular forces, so temperature remains constant.

What is the melting point of water at standard atmospheric pressure?

0 °C.

What is the boiling point of water at standard atmospheric pressure?

100 °C.

What happens during condensation?

Particles lose kinetic energy and move closer together to form a liquid.

What is the process of solidification/freezing?

Particles lose energy, slow down, and arrange into a fixed pattern.

What is evaporation?

The escape of more energetic particles from the surface of a liquid.

Why does evaporation cause cooling?

Higher-energy particles leave, lowering the average kinetic energy of the remaining particles.

What is the difference between boiling and evaporation?

Boiling occurs throughout the liquid at boiling point; evaporation occurs at the surface at any temperature.

What factors increase the rate of evaporation?

Increased temperature, increased surface area, and increased air movement.

What does the heating/cooling curve represent?

The changes in temperature and state of a substance over time.

What happens during the melting phase according to the heating curve?

Temperature remains constant as the solid melts into a liquid.

What happens during boiling in the heating curve?

Temperature remains constant as the liquid boils into gas.

What is conduction?

The transfer of thermal energy through a material, primarily in solids.

How do good conductors transfer energy?

Metals transfer energy effectively through delocalised electrons and collisions between particles.

Why are gases and liquids poor conductors?

Particles are further apart, resulting in less frequent collisions and slower energy transfer.

What is the mechanism of convection?

Heated fluid expands, becomes less dense, rises, and is replaced by cooler, denser fluid.

What is radiation?

Thermal energy transfer through infrared waves that does not require a medium.

What determines a good emitter of thermal radiation?

Dull, black surfaces are good absorbers/emitter of thermal radiation.

What determines a poor absorber of thermal radiation?

Shiny, white surfaces are good reflectors and poor absorbers.

How does the rate of energy emission relate to temperature?

Rate of emission increases with surface temperature or surface area.

What is a practical application of conduction in kitchenware?

Metal base for efficient heating, with plastic handles for insulation.

How does convection work in a room heater?

It heats air near the floor, causing it to rise and create a current to circulate warm air.

How does conduction occur in a fire?

Through solid fuel as heat is transferred to surrounding objects.

How does convection occur in a fire?

Hot air and smoke rise due to decreased density.

How does radiation transfer heat from a fire?

Heat is radiated to surrounding people and objects.

What is the equation for temperature conversion from Celsius to Kelvin?

T (in K) = θ (in °C) + 273.

What is the equation for Boyle's Law?

p1V1 = p2V2.

What is the equation for calculating specific heat capacity?

ΔE = m c Δθ.

What is the equation for electrical energy?

ΔE = VIt or ΔE = Pt.