How many kilojoules are required to change 85g of water at 25 C to steam at 100 C?
q1 = heat required to change T from 25 C to 100 c.
q1 = mass H2O x specific heat water x delta T.
q2 = heat required to change liquid water at 100 C to steam at 100 C.
q2 = mass H2O x heat vaporization
total heat = q1 + q2.
To find the amount of energy required to change the temperature of a substance, you can use the specific heat capacity formula. The specific heat capacity of water is approximately 4.186 J/g°C.
First, calculate the energy required to raise the temperature of the water from 25°C to 100°C:
Energy = mass × specific heat capacity × temperature change
Given:
Mass of water = 85g
Specific heat capacity of water = 4.186 J/g°C
Temperature change = 100°C - 25°C = 75°C
Energy = 85g × 4.186 J/g°C × 75°C
Energy = 263,354.25 J
Since the given mass is in grams and the specific heat capacity is in joules per gram and degree Celsius, the resulting energy is in joules.
To convert the energy to kilojoules, divide the result by 1000:
Energy in kilojoules = 263,354.25 J / 1000
Energy in kilojoules = 263.35425 kJ
Therefore, it requires approximately 263.354 kilojoules to change 85g of water at 25°C to steam at 100°C.