To calculate the heat capacity, we can use the formula:q = mcTwhere q is the heat capacity, m is the mass of the substance in grams , c is the specific heat capacity of the substance for water, it's 4.18 J/gC , and T is the change in temperature.In this case, the mass of water m is 25 grams, the specific heat capacity c is 4.18 J/gC, and the change in temperature T is 50C - 20C = 30C.Now, we can plug these values into the formula:q = 25 g 4.18 J/gC 30C q = 25 4.18 30q = 3135 JSo, the heat capacity of 25 grams of water when its temperature rises from 20C to 50C is 3135 Joules.