Question

a. the temperature of 200g of water increases from 20 ⁰C to 50 ⁰C in 10 minutes. Calculate:

i. the amount of heat gained by the water

ii. the average rate at which the water is gaining heat

(specific heat capacity of water = 4200 J kg^{-1 0}C^-1)

b. Determine the amount of heat that must be removed from 1 kg of water at 40 ⁰C to convert it to ice at -5 ⁰C.

(Obtain any relevant data that you need from the internet. Cite the source of that data in your answer)

Answer 1

a)

(i) the amount of heat gained by the water

$$Q=cm\Delta t=4200*0.2*(50-20)=25200\:\rm J$$

(ii) the average rate at which the water is gaining heat

$$P=\frac{Q}{\tau}=\frac{25200}{10*60}=42\:\rm W$$

b)

$$Q=c_wm\Delta t_1+\lambda m+c_{ice}m\Delta t_2\\ =4200*1*40+330000*1+2100*1*5\\ =508500\:\rm J$$