Conservation of Mass

1
Conservation of Mass
Why mass does not change in a closed system.
2
What Does the Law Say?

• Law of Conservation of Mass/Matter
• In a closed system, matter can be neither created
  nor destroyed, regardless of what is happening
  inside the system.
• Since matter can not be created or destroyed,
  mass can not change.

3
What Does that Mean?

• A Closed System-
• A contained area where matter can not escape
• Example- water inside a sealed bottle. If
  evaporation occurs, the water vapor (water as a
  gas) can not escape.
• Matter can not spontaneously be created inside
  the bottle, nor can it be destroyed.

4
What Does that Mean?

• Matter can change form.
• Examples
• Solids can melt into liquids
• Liquids can become gasses
• Wood can burn and become ash, carbon dioxide and
  water vapor
• In each example the matter changes what it looks
  like, but there is still the same amount.

5
What Does that Mean?

• Because the amount of matter stays the same, the
  mass of the system remains the same.
• Remember that mass measures the amount of matter.

6
Mass Remains Constant
If a Water bottle was on top of a triple-beam
balance and the cap was sealed, the matter could
not escape. Some of the water could evaporate
(change its appearance), but it would remain in
the bottle.
Therefore the balance continues to read the same
mass.
7
Review

• Conservation of Mass
• In a closed system, matter can not be created
  nor destroyed, it just changes appearance.
• Since the amount of matter does not change, the
  mass does not change.