Changes of StateEdexcel IGCSE Physics: Flashcards
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What happens to the temperature of a substance during a change of state, even while it is being heated?
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- What happens to the temperature of a substance during a change of state, even while it is being heated?
- The temperature stays constant, because the energy supplied is used to change the arrangement of particles, not to raise their kinetic energy.
- Define melting.
- The change of state from solid to liquid, occurring at a fixed melting point.
- Define boiling.
- The change of state from liquid to gas, occurring throughout the liquid at a fixed temperature (the boiling point).
- How does evaporation differ from boiling?
- Evaporation occurs only at the surface of a liquid and can happen at any temperature below the boiling point; boiling occurs throughout the liquid at a fixed temperature.
- Describe the arrangement and motion of particles in a solid.
- Regularly arranged, closely packed, and vibrating about fixed positions.
- Describe the arrangement and motion of particles in a liquid.
- Randomly arranged but close together, moving around and sliding past each other.
- Describe the arrangement and motion of particles in a gas.
- Randomly arranged, far apart, moving freely at high speed in all directions.
- Define specific heat capacity.
- The energy required to raise the temperature of 1 kg of a substance by 1°C, measured in J/kg°C.
- State the equation for calculating energy transferred using specific heat capacity.
- ΔQ = m × c × ΔT
- What does a flat section on a temperature-time heating graph indicate?
- The substance is undergoing a change of state (melting or boiling) — energy is still being supplied, but it is used to change particle arrangement, not raise temperature.
- Calculate the energy needed to raise 3 kg of water (c = 4200 J/kg°C) by 10°C.
- ΔQ = m × c × ΔT = 3 × 4200 × 10 = 126,000 J
- How can specific heat capacity be measured experimentally?
- Heat a known mass of material with a known electrical power for a measured time, record the temperature rise, and calculate c using ΔQ = m × c × ΔT.