Question

7. When you heat water from just above its freezing point to just below its boiling point, the kinetic energy of the molecules

(a) increases by about 18% (b) decreases by about 18% (c) doubles (d) it is impossible to say given this information

8. Anna’s body consists, roughly speaking, of 60 kg of water at human body temperature (37 C). Suppose Anna is standing next to a small frozen pond containing 200 kg of ice at 0 C. Which of the following is true?

(a) The total heat energy of Anna’s body is less than the total heat energy of the ice in the pond.

(b) The total heat energy of Anna’s body is the same as the total heat energy of the ice in the pond.

(c) The total heat energy of Anna’s body is greater than the total heat energy of the ice in the pond.

9. The linear expansion coefficient of steel is about 10^-5 . If a piece of railway line 500 m long is laid down in the winter when the temperature is −5 C, by how much will the length of the line increase when summer comes and the temperature reaches 35 C?

(a) 1 cm (b) 2 cm (c) 20 cm (d) 10 cm

10. Lake Michigan’s average depth is about 100 m. If the temperature of the water increases by by 2.5 C, by how much (to 20% accuracy) will its depth change?

(a) 0.5 cm (b) 12 cm (c) 1.2 cm (d) 4 cm

Answer 1

7. The kinetic energy of the molecules depends on the temperature. hence, the values of the temperatures must be given to find the kinetic energy. Therefore, more information needed to find the kinetic energy of the molecules.

Hence, the correct option is D.

8. Unless the two bodies of the different temperatures comes in contact with one another, the heat transfer does not takes place. Here, the person is standing next to the lake but not in contact with the lake. Hence, the anna's body will have the greater heat energy compared to the lake as lake is at zero degrees.

Therefore, the correct option is C.