# Question 1fa63

May 15, 2017

#### Answer:

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.

$2 {H}_{2} + 1 {O}_{2} = = = = 2 {H}_{2} O$

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

${H}_{2} O \left(l\right) + h e a t = = = {H}_{2} O \left(g\right)$

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

$2 N a \left(s\right) + 1 C {l}_{2} \left(g\right) = = = 2 N {a}^{+} C {l}^{-}$

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))#