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

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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