What is the main difference between a chemical and a physical change? PLEASE HELP ASAP

In a chemical change the nature of the substance changes and it is transformed, for example when a piece of wood is burned, the carbon is being transformed into carbon dioxide. A physical change is one where the nature of matter does not vary.

I hpoe help you.

physical changes only change the appearance of a substance not it's chemical composition .chemical changes change the substance with a new chemical formula

Explanation:

the correct option is c.

isotopes refers to different forms of the same element with the same atomic number but different mass number as a result of difference in their neutron numbers. isotopes have different relative atomic mass but share the same chemical properties.

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.