Question 2
2
Fig. 2.1 shows a laboratory thermometer that is calibrated to measure temperature in degrees Celsius. The thermometer makes use of the fact that the density of mercury varies with temperature.
structured3 marks
Question 2(b)
2(b)
The thermometer is initially at \(23.0^{\circ} \mathrm{C}\), as shown in Fig. 2.1. It is used to measure the temperature of an insulated beaker of water that is at \(37.4^{\circ} \mathrm{C}\). The bulb of the thermometer is inserted into the water, and the water is stirred until the reading on the thermometer becomes steady. The mass of water in the beaker is 18.7 g . The mass of mercury in the thermometer is 6.94 g . The specific heat capacity of water is \(4.18 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1}\). The specific heat capacity of mercury is \(0.140 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1}\). The glass of the thermometer and the beaker containing the water can be considered to have negligible heat capacity.
structured3 marks
Question 2(b)(i)
2(b)(i)
Calculate, to three significant figures, the final steady temperature indicated by the thermometer in the water. \({ }^{\circ} \mathrm{C}\)
Mediumstructured3 marks
Answer
\(Q=m c \Delta T\) C1 evidence of realisation that Q lost by water =Q gained by mercury C1 \(18.7 \times 4.18 \times(37.4-T)=6.94 \times 0.140 \times(T-23.0)\) C1 \(T=37.2^{\circ} \mathrm{C}\) A1
Question 18
18
Below are four short paragraphs describing the molecules in a beaker of water at \(50^{\circ} \mathrm{C}\). Which paragraph correctly describes the molecules? The molecules all travel at the same speed. This speed is not large enough for any of the molecules to leave the surface of the water. There are attractive forces between the molecules. The molecules have a range of speeds. Some molecules travel sufficiently fast to leave the surface of the water. There are no forces between the molecules. The molecules have a range of speeds. Some molecules travel sufficiently fast to leave the surface of the water. There are attractive forces between the molecules. The molecules have a range of speeds. The fastest molecules are unable to leave the surface of the water. There are attractive forces between the molecules.
Mediummcq1 marks
Answer
C
Question 19
19
The diagram shows an ice cube floating in water. Both the ice cube and the water are at \(0^{\circ} \mathrm{C}\). Which statement correctly compares the molecular properties of the ice and those of the water? The mean inter-molecular potential energies are the same for both the ice molecules and the water molecules. The mean inter-molecular separations are the same for both the ice and the water. The mean kinetic energies are the same for both the ice molecules and the water molecules. The mean total energies are the same for both the ice molecules and the water molecules.
Mediummcq1 marks
Answer
C
Question 10
10
An electronic sensor may be represented by the block diagram of Fig. 10.1.
structured1 marks
Question 10(a)
10(a)
State suitable sensing devices, one in each case, for the detection of
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Question 10(a)(i)
10(a)(i)
change of temperature,
Easystructured1 marks
Answer
thermistor/thermocouple ..... B1 ..... [1]