4. Anh measured the temperature of a pond near his house. Before he left for school, the water in the pond was 18°C. When he came home from school, the temperature of the pond was higher than it
was in the morning. What happened to the water molecules while he was at school?

The water molecules must have gained more thermal energy while Anh was away from the house.

An increase in the temperature of a body means that the body has gained more energy in the form of heat, also known as thermal energy.

The thermal energy represents the characteristic of a body responsible for its temperature.

An increase in the temperature of the water molecules increases their kinetic energy and, thus, makes the water molecules move around faster than before.

More on thermal energy can be found here: link

h let me think

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.