Temperature, heat and thermal energyIB MYP Physics: Flashcards
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What does temperature measure?
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- What does temperature measure?
- The average kinetic energy of the particles in a substance.
- What is thermal energy and what unit is it measured in?
- The total energy of all the particles in a substance, measured in joules (J).
- What are the units for temperature?
- Degrees Celsius (°C) or kelvin (K).
- Convert 25 °C into kelvin.
- 25 + 273 = 298 K.
- What are the two fixed points of the Celsius scale?
- 0 °C (ice melting) and 100 °C (water boiling).
- In which direction does thermal energy flow?
- From a region of higher temperature to a region of lower temperature.
- What is thermal equilibrium?
- The state in which two objects are at the same temperature, so there is no net transfer of thermal energy.
- Why can a swimming pool hold more thermal energy than a cup of boiling water?
- The pool has far more particles, so its total energy is larger even though its temperature is lower.
- Why do substances expand when heated?
- The particles gain energy and move further apart on average.
- Which state of matter expands the most when heated?
- Gases.
- How does a liquid-in-glass thermometer work?
- The liquid expands as it warms and rises up the narrow tube.
- What is a bimetallic strip?
- Two different metals joined together that bends when heated because they expand by different amounts.
- Why are gaps left in bridges and railway lines?
- To allow the metal to expand on hot days without buckling.
Exam questions on Temperature, heat and thermal energy
- A student places a metal spoon heated to 90 °C into a beaker of cold water at 20 °C and records the temperature of the water every minute until the readings stop changing.Explain, in terms of particles, why thermal energy is transferred from the spoon to the water.2 marks
- A swimming pool at 28 °C holds about 500 000 litres of water. A cup of tea at 80 °C holds about 0.25 litres of water.The tea is poured into the pool. Explain why energy flows from the tea to the pool even though the pool has more thermal energy.2 marks
- A student investigates how the length of an aluminium rod changes when it is heated. The rod is 1000 mm long at 20 °C. The increase in length was 0.9 mm for a 40 °C rise in temperature, 1.8 mm for an 80 °C rise, 2.8 mm for a 120 °C rise and 3.7 mm for a 160 °C rise.State a testable hypothesis for this investigation, giving a scientific reason, and name one variable that must be controlled.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).