Unit 4: Topic 4 - Physical and Chemical Changes

Question 1

What are physical and chemical changes?

Answer 1

Chemical changes typically involve the breaking/forming of chemical bonds (intramolecular). New substances are created, and the process is usually irreversible.
Ex: Nail rusting, dough baked into bread, burning

Physical changes typically involve the breaking/forming of intermolecular forces. The substance maintains its chemical composition, and the process is usually easily reversible.
Ex: Phase changes, cutting paper, crushing

Here is a table to summarize.

Question 2

What is an example of a change that can be both physical and chemical?

Answer 2

Sometimes physical processes involve the breaking of chemical bonds. For example, the dissolution of salt in water could be argued as either a physical or chemical process. It can be physical since it is a phase change that could be reversed through boiling/evaporation, but it can also be chemical as it involves the dissolution of salt into Na+ and Cl- ions.