Specific heat capacityIB MYP Physics: Subtopic test

1. 1
   On a sunny afternoon in Dubai, the sand on a beach becomes too hot to walk on, while the sea water beside it feels pleasantly cool. Each kilogram of sand and each kilogram of sea water absorbs about the same amount of energy from the Sun.

   (a)

   Which statement gives the definition of the specific heat capacity of a substance?

   [1 mark]

   • AThe energy needed to melt 1 kg of the substance without any change in temperature
   • BThe energy needed to raise the temperature of 1 kg of the substance by 1 °C
   • CThe temperature rise produced when 1 J of energy is supplied to the substance
   • DThe total energy stored in the substance at a particular temperature

   (b)

   Which unit is used for specific heat capacity?

   [1 mark]

   • AJ/°C
   • Bkg °C/J
   • CJ kg °C
   • DJ/kg °C

   (c)

   Explain why the temperature of the sand rises by much more than the temperature of the sea water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An electric kettle contains 1.5 kg of water at 20 °C. The heating element has a power of 2000 W. The specific heat capacity of water is 4200 J/kg °C, and the water must reach 100 °C to boil.

   (a)

   How much energy must be transferred to the water to raise it from 20 °C to 100 °C?

   [1 mark]

   • A504 000 J
   • B126 000 J
   • C630 000 J
   • D6300 J

   (b)

   Assuming all of the energy from the element is transferred to the water, how long does the kettle take to heat the water from 20 °C to 100 °C?

   [1 mark]

   • A315 s
   • B63 s
   • C252 s
   • D0.004 s

   (c)

   In practice the kettle takes longer than the time calculated. Explain why.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student measures the specific heat capacity of aluminium using a block of mass 1.00 kg. The block has two holes: one holds a 12 V electric heater and the other holds a thermometer. The heater carries a current of 5.0 A for 300 s. The block is not insulated, and its temperature rises from 20.0 °C to 39.0 °C.

   (a)

   Calculate the specific heat capacity of aluminium from the student's results. Give your answer to three significant figures.

   [3 marks]

   (b)

   The accepted value for aluminium is 900 J/kg °C. Explain why the student's value is higher, and suggest two improvements to the method.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school in Chile plans to store solar energy as heat so that its classrooms stay warm at night. The design team is comparing a large tank of water with a large tank of cooking oil. Water has a specific heat capacity of 4200 J/kg °C and cooking oil has a specific heat capacity of about 2000 J/kg °C.

   (a)

   The science club decides to test the two liquids first. Design an investigation to compare how much the temperature of equal masses of water and cooking oil rises when they are heated. Include a hypothesis, the variables and a safe method.

   [6 marks]

   (b)

   Discuss the advantages and disadvantages of using water to store the solar energy, and evaluate whether the school should use it.

   [6 marks]

   Total for question 4: 12 marks

End of questions