Question 9
- Explain the terms
- Thermal equilibrium
- Fundamental interval
- List two uses of the hydraulic press
- Name the material used to reset the steel index in the Six’s maximum and minimum thermometer
- (i) A nursing mother prepared her baby’s milk mixture at 85oC, in a feeding bottle. In order to cool it to 40oC, she immersed the bottle in an aluminum bowl of heat capacity 90 J K-1 containing 500 g of water at 26oC. If the mass of the mixture is 300g, calculate the specific heat capacity of the mixture.
[Neglect heat losses and heat capacity of the bottle; specific heat capacity of water = 4200 J kg-1 K-1]
(ii) (α) Name two ways through which the bottle losses heat.
(β) Name two industrial processes in which heat exchanger is used.
Observation
Part (a) (i) Very few candidates got acceptable response to score full marks. They failed to realize that more details are expected to “explain” than to “define”. Performance was extremely low.
(ii) Many candidates had no difficulty in this part. However, candidates
who defined fundamental interval as the distance between the upper and lower fixed points did not receive any mark. Performance was low.
Part (b): This question was a popular question but majority of the candidates managed to mention only one use correctly.
Part (c): The performance of candidates was satisfactory.
Part (d) (i): Candidates performance was average. Many understood that the problem was a case of heat lost equals heat gained but some forgot to include the given thermal capacity and failed to convert grams to kilograms.
(ii)(α) Many candidates performed well as over 70% scored the full mark.
(β) Many candidates performed well while some candidates skipped this part.