Final answer:
To heat 2 kg of water from 20°C to 70°C, it will require 420 kJ of energy.
Step-by-step explanation:
To calculate the energy required to heat 2 kg of water from 20°C to 70°C, we can use the equation:
q = mcΔT
Where q is the amount of energy, m is the mass of the water, c is the specific heat of water, and ΔT is the temperature change.
Given that the specific heat of water is 4.2 kJ/°C•kg, we can substitute the values into the equation:
q = (2 kg)(4.2 kJ/°C•kg)(70°C-20°C)
q = 2 kg * 4.2 kJ/°C•kg * 50°C
q = 420 kJ
Therefore, it will take 420 kJ of energy to heat 2 kg of water from 20°C to 70°C.