When 20 grams of water is cooled from 20 C to 10 C the number of joules of heat released is?

To calculate the heat released when cooling water, you can use the formula: Q = mcΔT, where Q is the heat energy, m is the mass of the substance (20g in this case), c is the specific heat capacity of water (4.18 J/g°C), and ΔT is the change in temperature (10°C in this case). Plugging in the values, we get Q = 20g x 4.18 J/g°C x 10°C = 836 J. Therefore, 836 joules of heat are released when 20 grams of water is cooled from 20°C to 10°C.