Temperature exam q's

Question 1

How would you demonstrate the principle of operation of a thermocouple?

Answer 1

• One junction kept cold
• Other junction heated
• emf - meter reading

Question 2

What is the thermometric property of (i) a mercury thermometer, (ii) a thermocouple?

Answer 2

(i) Length of a column

(ii) emf

Question 3

Give two precautions that were taken to minimise heat loss to the surroundings. (specific heat capacity of water exp.)

Answer 3

• Insulate calorimeter

- Transfer copper pieces quickly

Question 4

Heat energy can be transferred by conduction, convection and radiation.

Answer 4

Conduction: The transfer of heat energy through a body without visible motion of any part of the body due to a temperature difference within the body.
Convection: The transfer of heat in a fluid by circulation of the fluid itself.
Radiation: The transfer of heat between two points by means of electromagnetic radiation.

Question 5

Explain how the u-value of a structure is reduced by adding insulation to it.

Answer 5

U-value refers to Unit Heat Loss Rate. A good insulating structure therefore has a low U-value.

Question 6

Explain why on a hot day, the water on the surface of a still lake is usually warmer than the water some distance below the surface.

Answer 6

• Conduction is poor
• Convection currents go up not down
• Warm water is less dense and does not sink

Question 7

Explain why on a hot day, the sea is usually colder than the land.

Answer 7

Large bodies of water have higher thermal capacities than land due to their immense density. As a result..

Question 8

In an experiment to determine the specific latent heat of fusion of ice, state two ways in which the calorimeter could have been insulated.

Answer 8

• Lag the calorimeter

- Lid

Question 9

In an experiment to determine the specific latent heat of water, give two precautions that were taken to minimise heat loss to the surroundings.

Answer 9

• The calorimeter was insulated and a lid was placed on it.

- The copper was transferred quickly once removed from boiling.

Question 10

In an experiment to determine the specific latent heat of water, describe how the copper was heated and how its temperature was measured.

Answer 10

The copper was placed in a boiling tube, plugged with cotton wool, and then placed into a beaker of boiling water for 5 mins. A thermometer was also left in the boiling tube and it recorded the temperature of the copper.

Question 11

In an experiment to measure the specific latent heat of vaporisation of water, how was the steam dried?

Answer 11

Use of steam trap

Question 12

In an experiment to determine the specific heat capacity of water, what effect would increasing the current flowing through the coil for the same temperature rise have on the accuracy of your result. Why?

Answer 12

Higher current, more energy released - temp rises more quickly - less time for heat loss or gain to surroundings.

Question 13

Explain why heat does not travel through solids by means of convection.

Answer 13

The particles cannot move freely

Question 14

Storage heaters are frequently used to heat buildings. State the principle that underlies the operation of an electrical storage heater.

Answer 14

Large heat capacity - heated when electricity is inexpensive and stores a large quantity of energy.

Question 15

What is the principle of a heat pump?

Answer 15

Transfer heat from a cooler region to a warmer region.

Question 16

In an experiment to measure the specific capacity of a liquid, if a joulemeter was not available how would the electrical energy supplied be measured?

Answer 16

Voltmeter and ammeter and timer

Question 17

Name two thermometric properties.

Answer 17

• Length of mercury column

- emf thermocouple

Question 18

Distinguish between heat and temperature.

Answer 18

• Heat is a form of energy

- Temperature is a measure of hotness or coldness in a body.

Question 19

Give the equation that defines temperature on the Celcius scale.

Answer 19

273 K = 0°C 

Question 20

What is needed to establish a temperature scale?

Answer 20

Thermometric property and 2 fixed points and a scale.

Question 21

Why are storage heaters surrounded by bricks of high specific heat capacity?

Answer 21

Bricks slowly release their heat.

Question 22

Explain how a heat pump works. What is the principle on which it work?

Answer 22

Pumps energy from a cooler region to a warmer region.

Question 23

Give a practical application of a heat pump.

Answer 23

Fridge

Question 24

Name the three methods of heat transfer.

Answer 24

• Conduction, convection and radiation

Question 25

Describe how the mass of the steam was determined.

Answer 25

Final mass of calorimeter plus water - initial mass of calorimeter and water.

Question 26

In an experiment to measure the specific heat capacity of a liquid, describe the apparatus which might have been used in this experiment in addition to the calorimeter.

Answer 26

• Power supply, joulemeter
• Liquid, heating coil
• Thermometer, insulation

Question 27

In an experiment to measure the specific heat capacity of a liquid, give three ways in which heat losses from the calorimeter might have been reduced.

Answer 27

• Lid on calorimeter
• Place calorimeter in a beaker surrounded by plenty of cotton wool to insulate it
• Cooling the calorimeter and liquid below r.t before supplying the heat is neither lost or gained to surroundings

Question 28

In an experiment to measure the specific heat capacity of a liquid, explain why using a larger mass of the liquid while supplying the same amount of energy might hace produced a less accurate result.

Answer 28

• Smaller rise in temperature

- Large % error

Question 29

Why is the bottom of a flat-plate collector blackened?

Answer 29

Good absorber of heat

Question 30

Name the three ways that heat could be lost from a vacuum-tube solar collector.

Answer 30

Convection, conduction, radiation

Question 31

The liquid in a vacuum-tube solar collector has a large specific latent heat of vaporisation. Explain why.

Answer 31

More energy released during change of state.

Question 32

How is the sun’s energy trapped in a vacuum-tube solar collector?

Answer 32

• Silvered walls prevent radiation

- Evacuated walls prevent conduction and convection

Question 33

Give an advantage of a geothermal heating system over a solar heating system.

Answer 33

• Geothermal system functions all the time

- Solar heating system works only during daytime

Question 34

State two reasons why the ice was crushed before adding it to the water.

Answer 34

• To melt quickly

- To ensure all ice is at 0°C

Question 35

Some students in the class used cold water instead of warmed water. They noted that there tiny drops of water on the outside of the calorimeter at the end of the experiment, where did this water come from?

Answer 35

Condensation from the air

Question 36

Some students in the class used cold water instead of warmed water. They noted that there tiny drops of water on the outside of the calorimeter at the end of the experiment, how did it affect the result of the experiment?

Answer 36

• Extra heat given to the calorimeter

- Incorrect higher final temperature

Question 37

In an experiment to measure the specific latent heat of fusion of ice, explain why warm water was used.

Answer 37

To speed up melting of the ice.

Question 38

In an experiment to measure the specific latent heat of fusion of ice, what should be the approximate r.t to minimise experimental error?

Answer 38

21°C (midway between initial and final temperatures)

Question 39

Why is a filament light bulb not an efficient source of light?

Answer 39

The light energy production is only a small percentage.

Question 40

In reality, the time taken to heat the water will be greater. Explain why.

Answer 40

ENERGY will be lost to surroundings.

Question 41

Explain how this graph verifies Joules law.

Answer 41

Straight line through origin.

Question 42

Why was a fixed mass of water used throughout the experiment?

Answer 42

Temperature and current are the variables

Question 43

A thermometer with a low heat capacity was used to ensure accuracy. Explain why.

Answer 43

Absorbs less heat from water.