Changes of State

Changes of State

Changes of State, figure 1

Looking at the second bullet point in more detail, the reason for this is because the number of molecules never changes. If a solid has 100 molecules and it melts it will still have 100 molecules which means it has the same mass.

Let’s say if then boils and turns into a gas, how many molecules will it have?

You’re right! Still 100!! Therefore the mass it still the same.

What is a reversible change?
recover its original properties
Explanation: The substance will recover its original properties
What is a chemical change?
Your answer should include: cannot be reversed / irreversible
Explanation: The process cannot be reversed to recover the original properties