Question

In an experiment, 120 g of ice at 0 °C is to be melted. The specific latent heat of

ice is 340 J/g. Assume that all the energy from the heater will be used to melt
the ice.
Q1) Calculate the expected time for which the 60 W heater is switched on.​

Answer 1

`680\; \rm s`.

Step-by-step explanation:

Start by finding the total amount of energy required for melting that much ice.

`\begin{aligned}&\text{Energy required for melting ice sample} \\ &= \text{Mass of Ice} * \text{Specific Latent Heat of Ice} \\ &= 120\; \rm g * 340\; \rm J \cdot g^(-1) = 4.08 * 10^(4)\; \rm J \end{aligned}`.

Hence, the heater would need to supply (at least)
`4.08 * 10^(4)\; \rm J` of energy.

The power of the heater is
`60\; \rm W`, which is equivalent to
`60\; \rm J \cdot s^(-1)`, In other words, the heater is rated to supply
`60\; \rm J` of energy every second.

Amount of time it takes for the heater to supply
`4.08 * 10^(4)\; \rm J` at
`60\; \rm J \cdot s^(-1)`:

`\begin{aligned}(4.08 * 10^(4)\; \rm J)/(60\; \rm J \cdot s^(-1)) = 680\; \rm s\end{aligned}`.

Hence, it would take
`680\; \rm s` for the heater to melt the ice if the heater is insulated, and all the energy from the heater went to the ice.