States Physics

What is specific heat capacity?

The energy required to change the temperature of 1 kg of a substance by 1°C. Units: J/kg°C

What is absolute zero?

The lowest possible temperature, –273°C (0 K), where particles have minimum kinetic energy.

What does the Kelvin temperature of a gas represent?

It is proportional to the average kinetic energy of the gas molecules.

Why does temperature stay constant during a change of state?

Energy is being used to break bonds between particles, not to increase kinetic energy.

What happens to gas molecules when temperature increases?

Their average speed increases, so they hit the container walls harder and more often, increasing pressure.

How does a gas exert pressure on a container?

Gas molecules move randomly and collide with the walls, exerting a force — many collisions per second create pressure.

Describe the arrangement and motion of particles in a solid.

Closely packed in a regular pattern, vibrating in fixed positions.

Describe the arrangement and motion of particles in a liquid.

Close together but randomly arranged, free to move and flow past each other.

Describe the arrangement and motion of particles in a gas.

Far apart, moving rapidly and randomly in all directions.

What happens to particles when a solid melts?

They gain enough energy to break free from fixed positions and move around — becoming a liquid.

What is the difference between evaporation and boiling?

Evaporation happens at the surface at any temperature. Boiling happens throughout the liquid at a fixed temperature.

What is the equation for change in thermal energy?

ΔQ = m × c × ΔT (energy in J, mass in kg, c in J/kg°C, temperature in °C)

What is the equation for pressure difference in a fluid?

p = h × ρ × g (height in m, density in kg/m³, g in N/kg)

What is the equation for Gay-Lussac's Law (pressure/temperature)?

p₁/T₁ = p₂/T₂ — temperature must be in Kelvin

What is Boyle's Law (pressure/volume)?

p₁V₁ = p₂V₂ — temperature must be constant

In what directions does pressure act at a point in a fluid at rest?

Equally in all directions.

What is the basic principle of hydraulics?

Pressure is transmitted equally through a fluid, allowing a small force over a small area to produce a large force over a large area.

What is the qualitative relationship between pressure and volume at constant temperature?

As volume increases, pressure decreases (and vice versa) — they are inversely proportional.

What is the qualitative relationship between pressure and temperature at constant volume?

As temperature (in Kelvin) increases, pressure increases — they are directly proportional.