Question

Question #1fa63

Answer 1

A chemical change is a change in the composition of atoms that make up a compound, or element, A physical change is a change in the state of the compound or element with no change in composition.

Explanation:

A chemical change like the formation of water has a change in the composition of the atoms.

`2 H_2 + 1 O_2 ==== 2 H_2O`

The diatomic molecules of the elements Oxygen and Hydrogen have been changed into a triatomic Compound of Water
This is a chemical change.

A physical change like the evaporation of water has a change in the physical state of the compound

`H_2O(l) + heat=== H_2O(g)`

This is a physical change because the chemical composition of the water has not changed. but it has changed state from a liquid to a solid.

A chemical change is the formation of salt sodium chloride

`2 Na(s) + 1 Cl_2(g) === 2 Na^+Cl^-`

This is a chemical change because the two dangerous elements have become a beneficial compound salt.

A physical change is the formation of salt water.

`Na^+Cl^-(s) + H_2O == Na^+(aq) + Cl^-_(aq))`