How much heat (in joules) is required to boil 250 grams of water that starts at 25C completely to steam? Use 4.2 J/gC for the specific heat
To calculate the heat required to boil water, you need to consider two steps:
1. Heat required to raise the temperature of water from 25°C to its boiling point.
2. Heat required to convert the water at its boiling point into steam.
Let's break down the calculation step by step:
Step 1: Calculate the heat required to raise the temperature of water from 25°C to its boiling point.
First, determine the temperature change:
Temperature change = final temperature - initial temperature
Temperature change = 100°C (boiling point) - 25°C
Temperature change = 75°C
Now, calculate the heat required using the specific heat formula:
Heat = mass x specific heat x temperature change
Given:
Mass of water = 250 grams
Specific heat = 4.2 J/g°C
Temperature change = 75°C
Heat required to raise the temperature = 250 g x 4.2 J/g°C x 75°C
Step 2: Calculate the heat required to convert water at its boiling point into steam.
To convert water at its boiling point into steam, you need to consider the heat of vaporization for water. The heat of vaporization for water is approximately 2.26 x 10^6 J/kg.
Convert the mass of water from grams to kilograms:
Mass of water in kg = 250 g / 1000
Mass of water in kg = 0.25 kg
Heat required to convert water to steam = mass x heat of vaporization
Heat required to convert water to steam = 0.25 kg x 2.26 x 10^6 J/kg
Add the heat required for both steps to get the total heat required:
Total heat = Heat required to raise the temperature + Heat required to convert water to steam
Finally, compute the total heat required.