Suppose a 4.0 kg mass of water gained heat and increased in temperature from 10°C to 15°C. The specific heat capacity of water is 4.186 kJ/kg°C. How much heat was gained by the water?

9.6 kJ
20 kJ
56 kJ
84 kJ

1 answer

To calculate the heat gained by the water, we can use the formula:

\[ Q = mc\Delta T \]

Where:

  • \( Q \) is the heat gained (in kJ),
  • \( m \) is the mass (in kg),
  • \( c \) is the specific heat capacity (in kJ/kg°C),
  • \( \Delta T \) is the change in temperature (in °C).

Given:

  • \( m = 4.0 , \text{kg} \)
  • \( c = 4.186 , \text{kJ/kg°C} \)
  • Initial temperature \( T_i = 10°C \) and final temperature \( T_f = 15°C \)

First, calculate the change in temperature:

\[ \Delta T = T_f - T_i = 15°C - 10°C = 5°C \]

Now we can plug these values into the formula:

\[ Q = (4.0 , \text{kg}) \times (4.186 , \text{kJ/kg°C}) \times (5°C) \]

\[ Q = 4.0 \times 4.186 \times 5 = 83.72 , \text{kJ} \]

Rounding this value, we find:

\[ Q \approx 84 , \text{kJ} \]

So, the heat gained by the water is 84 kJ.