Temperature, heat and thermal energyIB MYP Physics: Subtopic test

1. 1
   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.

   (a)

   In which direction is there a net transfer of thermal energy when the spoon is placed in the water?

   [1 mark]

   • AFrom the spoon to the water
   • BFrom the water to the spoon
   • CThere is no transfer of thermal energy
   • DEqually in both directions

   (b)

   What name is given to the state reached when the spoon and the water are at the same temperature and the readings stop changing?

   [1 mark]

   • AThermal expansion
   • BConduction
   • CEvaporation
   • DThermal equilibrium

   (c)

   Explain, in terms of particles, why thermal energy is transferred from the spoon to the water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   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.

   (a)

   Which statement about temperature is correct?

   [1 mark]

   • ATemperature is the total energy of all the particles
   • BTemperature is a measure of the average kinetic energy of the particles
   • CTemperature is measured in joules
   • DTemperature is the amount of heat an object contains

   (b)

   Which statement about the thermal energy of the pool and the tea is correct?

   [1 mark]

   • AThe tea has more thermal energy because it is hotter
   • BThey have the same thermal energy because they are both water
   • CThe pool has more thermal energy because it contains far more particles
   • DThe thermal energy cannot be compared

   (c)

   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]

   Total for question 2: 4 marks

3. 3
   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.

   (a)

   State a testable hypothesis for this investigation, giving a scientific reason, and name one variable that must be controlled.

   [3 marks]

   (b)

   Describe the pattern in the results, use it to predict the increase in length for a 200 °C rise, and suggest one improvement to the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A long steel road bridge is being built in a desert region of the UAE, where temperatures change from about 10 °C on winter nights to about 50 °C on summer afternoons. The engineers are fitting small gaps, called expansion joints, between the steel sections of the road. The bridge's control room also has a fire alarm that contains a bimetallic strip made from brass and steel.

   (a)

   Explain, in terms of particles, why the steel sections expand when the temperature rises, and describe how the bimetallic strip sets off the fire alarm in a fire.

   [6 marks]

   (b)

   Discuss and evaluate the decision to fit expansion joints in the bridge, even though they increase the cost.

   [6 marks]

   Total for question 4: 12 marks

End of questions