Question

It's possible to boil water by adding hot rocks to it, a technique that has been used in many societies over time. If you heat a rock in the fire, you can easily get it to a temperature of 500∘C. If you use granite or other similar stones, the specific heat is about 800 J/(kg⋅K).If 5.0 kg of water at 10∘C is in a leak-proof vessel, what minimum number of 1.0 kg stones must be added to bring the water to a boil?

Answer 1

Answer:

6

Explanation:

m = Mass

c = Specific heat

$\Delta T$ = Change in temperature

s denotes stone

Heat is given by

$Q=mc\Delta T\\\Rightarrow Q=5\times 4180\times (100-10)\\\Rightarrow Q=1881000\ J$

Heat for the stone

$Q=m_sc_s\Delta T\\\Rightarrow 1881000=m_s800\times (500-100)\\\Rightarrow m_s=\dfrac{1881000}{800\times (500-100)}\\\Rightarrow m_s=5.878125\ kg$

Number of stones is given by

$n=\dfrac{5.878125}{1}\\\Rightarrow n\approx 6$

The number of stones is 6