# How many joules does it take to melt 35 g of ice at 0° C?

##### 1 Answer

It takes 12,000 Joules of energy to melt 35 grams of ice at 0 °C

#### Explanation:

The enthalpy change for melting ice is called the entlaphy of fusion. Its value is 6.02 kj/mol. This means for every mole of ice we melt we must apply 6.02 kj of heat. We can calculate the heat needed with the following equation:

where:

In this problem we would like to calculate the heat needed to melt 35 grams of ice at 0 °C. This problem can be broken into three steps:

1. Calculate moles of water

2. multiply by the enthalpy of fusion

3. Convert kJ to J

**Step 1: Calculating moles of water**

**Step 2: Multiply by enthalpy of fusion**

**Step 3: Convert kJ to J**

Finally rounding to 2 sig figs (since 34°C has two sig figs) we get

For more examples on phase changes and enthalpy, see the video below:

One last note, if the temperature were not 0 °C then the ice would have to be heated in addition to melted. This would be a phase change problem combined with a heat capacity problem.