Help! Small question!
Give 2 examples of chemical changes that are reversible

Chemical reactions can only be undone by using other chemical reactions. For example:

A tarnished penny underwent a chemical change, but if you place it in vinegar another chemical change will take place as the vinegar mixes with the copper oxide of the tarnish, and the tarnish will be cleaned off.

Another example of a chemical change undoing a chemical change is combining hydrogen gas and iodine vapor to form hydrogen iodide. Eventually the hydrogen iodide will decompose, and turn back into hydrogen and iodine.

I hope this helps! has a wonderful day!

it may be wrong but i think its a

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.