The first question is asking which phase change occurs when steam is cooled to 100°C. The answer is condensation.
The second question is asking for the term that refers to the amount of energy needed to change a liquid into a gas, without changing its temperature. The answer is heat of vaporization.
The third question is asking in which phase change hydrogen bonds are formed. The answer is freezing.
The fourth question is asking for the amount of energy required to raise the temperature of 20 g of a substance from 72°C to 88°C, given that the specific heat of the substance is 0.215 J/g°C. To solve this problem, you can use the formula Q = m * c * delta T, where Q is the energy required, m is the mass of the substance, c is the specific heat, and delta T is the change in temperature. Plugging in the given values, you get Q = 20 g * 0.215 J/g°C * (88°C - 72°C) = 68.8 J. Therefore, the answer is 68.8 J.