What is a physical change? What is a chemical change? Provide two examples of each.

physical change is the temporary and reversible change in which no substance is formed.

eg - melting of ice, tearing paper into pieces, etc.

Chemical change is the permanent change in which new substance having different chemical properties are formed.

eg - burning of firewood, Rusting of iron, etc.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

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.

if it's not useful, feel free to report for mistake in answer.