Consider the heating curve for water. A graph of the heating curve for water has time in minutes on the horizontal axis and Temp
erature in degrees Celsius on the vertical axis. A line runs through the following points: 0 minutes, negative 20 degrees; 0.5 minutes, 0 degrees; 2 minutes, 0 degrees; 4 minutes, 100 degrees; 8 minutes, 100 degrees; 9.5 minutes, 160 degrees. At what temperature does the solid start melting? –20°C 0°C 20°C 80°C
In this case, given the heating curve of water on the attached document, we can notice that at 0 °C the solid starts melting, which means that the melting point is reached. Melting point is known as a physical change whereby a solid changes to liquid by the addition of heat as it allows the molecules to separate to each other.
The correct answer among the choices listed above is option D. The average kinetic energy of water molecules as water freeze <span>decreases as water releases energy to its surroundings. Energy is released as the molecules go into a more condensed phase which is the solid.</span>