Temperature and Thermal Expansion

14 Grade 10 Physics questions on Temperature and Thermal Expansion, with worked marking schemes. 14 questions are available on this topic in full.

1. Question 1

   4 marks

   Name the two fixed points used in calibrating a Celsius thermometer, and state the temperature assigned to each.

   (4 marks)

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2. Question 2

   1 mark

   A clinical thermometer used at a school dispensary has a very narrow constriction in the bore just above the bulb. The purpose of the constriction is to:

   A. stop the mercury thread running back into the bulb so the reading can be taken after the thermometer is removed.

   B. allow the thermometer to measure temperatures below room temperature.

   C. prevent the mercury from expanding past the highest mark on the stem.

   D. make the mercury expand faster when the bulb is warmed.

   (1 mark)

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3. Question 3

   1 mark

   Equal volumes of steel, glass, water and air are each warmed through the same rise in temperature. Which one increases in volume by the largest amount?

   A. The steel.

   B. The glass.

   C. The air.

   D. The water.

   (1 mark)

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4. Question 4

   3 marks

   Explain why a thick glass tumbler is likely to crack when very hot water is poured into it, while a thin glass one usually does not.

   (3 marks)

   Marking scheme

   1 mark: Glass is a poor conductor of heat, so heat travels slowly through the wall of the tumbler. 1 mark: In a thick tumbler the inner surface becomes hot and expands while the outer surface is still cool and has not expanded, so the unequal expansion sets up large stresses in the glass and it cracks. 1 mark: In a thin tumbler heat reaches the outer surface quickly, so both surfaces reach nearly the same temperature and expand by nearly the same amount, and little stress is produced.

5. Question 5

   4 marks

   A poultry brooder is kept at a steady temperature by a thermostat containing a bimetallic strip. Explain how the bimetallic strip switches the heater off and on as the temperature of the brooder changes.

   (4 marks)

   Marking scheme

   1 mark: The strip is made of two different metals, for example brass and invar, riveted firmly together along their length; the two metals have different linear expansivities. 1 mark: When the brooder gets too warm, the brass expands more than the invar, so the strip bends with the brass on the outside of the curve (it curves towards the invar). 1 mark: The bending moves the strip away from the electrical contact, breaking the circuit and switching the heater off. 1 mark: As the brooder cools, the strip straightens and touches the contact again, completing the circuit and switching the heater on, so the temperature of the chicks stays nearly constant.

6. Question 6

   1 mark

   A learner dips a thumb in warm water, removes it and immediately dips it in water from a tap. The tap water feels very cold, although a thermometer shows it is at room temperature. This observation shows that:

   A. the tap water is below 0 degrees Celsius.

   B. heat and temperature are the same physical quantity.

   C. the thumb gains heat from the tap water.

   D. the sense of touch is not a reliable way of judging temperature.

   (1 mark)

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7. Question 7

   4 marks

   Explain how the unusual (anomalous) expansion of water allows fish to survive in a lake whose surface water cools to freezing point.

   (4 marks)

   Marking scheme

   1 mark: As lake water cools it contracts and becomes denser until it reaches 4 degrees Celsius, at which temperature water has its maximum density. 1 mark: This densest water at 4 degrees Celsius sinks and collects at the bottom of the lake. 1 mark: On cooling further from 4 degrees Celsius to 0 degrees Celsius water expands instead of contracting (anomalous expansion), so this colder water is less dense, stays at the surface and freezes there first. 1 mark: Ice is less dense than water, so it floats and acts as an insulating layer that slows further cooling, leaving liquid water at about 4 degrees Celsius underneath in which the fish survive.

8. Question 8

   1 mark

   In a steel fabrication workshop, rivets are driven through holes in two steel plates while red hot and then hammered flat. The joint becomes very tight because, as the rivet cools, it:

   A. becomes brittle and grips the plates.

   B. expands and fills the hole completely.

   C. melts slightly and welds itself to the plates.

   D. contracts and pulls the two plates firmly together.

   (1 mark)

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9. Question 9

   2 marks

   Distinguish between heat and temperature.

   (2 marks)

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10. Question 10

    1 mark

    At midday the air temperature in Lodwar was recorded as 38 degrees Celsius. Expressed on the Kelvin scale, this temperature is:

    A. 338 K

    B. 235 K

    C. 311 K

    D. 305 K

    (1 mark)

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11. Question 11

    3 marks

    A straight steel water pipe at a tea factory is 30 m long when the morning temperature is 15 degrees Celsius. By the afternoon its temperature has risen to 55 degrees Celsius. Taking the linear expansivity of steel as $1.2\times 10^{-5}$ per kelvin, determine the increase in the length of the pipe.

    (3 marks)

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12. Question 12

    1 mark

    A copper rod and an iron rod of equal length are heated through the same rise in temperature. The copper rod is found to become longer than the iron rod. This is because copper has a:

    A. greater linear expansivity than iron.

    B. greater specific heat capacity than iron.

    C. lower melting point than iron.

    D. greater density than iron.

    (1 mark)

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13. Question 13

    1 mark

    The concrete slabs of a road surface are laid with narrow gaps between them, and the gaps are filled with a soft tar-like material. The gaps are left mainly to:

    A. drain away rain water from the road surface.

    B. increase the grip between the tyres and the road.

    C. allow the slabs to expand on hot afternoons without buckling.

    D. allow the slabs to be lifted out easily during repairs.

    (1 mark)

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14. Question 14

    3 marks

    State two advantages of using mercury rather than alcohol as the liquid in a laboratory thermometer, and state one situation in which alcohol would be the better choice.

    (3 marks)

    Marking scheme

    1 mark: Any one advantage - mercury is a good conductor of heat, so it responds quickly to temperature changes; or mercury does not wet (stick to) the glass, so readings are accurate; or mercury is opaque and shiny, so the thread is easily seen without dyeing; or mercury has a high boiling point (357 degrees Celsius), giving a wide upper range. 1 mark: A second, different advantage from the list above. 1 mark: Alcohol is better for measuring very low temperatures, for example the freezing night temperatures near Mount Kenya, because alcohol freezes at about -115 degrees Celsius while mercury freezes at about -39 degrees Celsius.

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