(a) Explain the terms:
(i) thermal equilibrium;
(ii) fundamental interval.
(b) List two uses of the hydraulic press.
(c) Name the material used to reset the steel index in the Six’s maximum and minimum thermometer.
(d)(i) A nursing mother prepared her baby’s milk mixture at 85°C, in a feeding bottle. In order to cool it to 40°C, she immersed the bottle in an aluminium bowl of heat capacity 90 JK\(^{-1}\) containing 500 g of water at 26°C. 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) (\(\alpha\)) Name two ways through which the bottle losses heat.
(\(\beta\)) Name two industrial processes in which heat exchanger is used.
Explanation
(a)(i) Thermal equilibrium is a condition in which two bodies in contact have no net flow of heat between them.
(ii) Fundamental interval is the difference in temperature between the lower fixed point, i.e. temperature of melting ice at standard atmospheric pressure and that upper fixed point, i.e. temperature of steam at standard atmospheric pressure.
(b) Uses of hydraulic press are:-
-Compressing metal sheets;
-Compressing soft materials into bales;
-Compressing paper in printing industries;
-Lifting of objects.
(c) The material used to reset the steel index in the six's maximum and minimum thermometer is magnet.
(d)(i) Heat lost by mixture = Heat gained by water + Heat gained by aluminium.
M\(_mC_w\Delta \theta_m\) + C\(_a\Delta\theta_a\)
0.3 x C\(_m\) x (85 - 40) = 0.5 x 4200 (40 - 26) + 90 (40 - 26)
13.5 C\(_m\) = 29400 + 1260
C\(_m\) = \(\frac{30660}{13.5}\)
= 2271.1 Jkg\(^{-1}\)K\(^{-1}\)
(ii) (\(\alpha\)) The bottle losses heat through conduction and convection. (\(\beta\)) Heat exchanger in: Incubation, refriaeration, air-conditioning, sewage treatment, cooling byradiators, generation of electricity, etc.