When we say that mass is conserved during a physical change , we mean that the total amount of matter stays the same before and after the change, even if its form or appearance looks different.

What Does ā€œMass Is Conservedā€ Mean?

During a physical change:

  • The mass before the change equals the mass after the change.
  • No particles are created or destroyed; they are only rearranged or spread out.
  • If the system is closed (nothing can enter or leave), the scale would show the same mass the whole time.

In simple terms: the stuff you start with is the same stuff you end with, just in a different form.

Physical Change vs How It Looks

A physical change can:

  • Change state : solid ā†’ liquid ā†’ gas (like ice ā†’ water ā†’ steam).
  • Change shape or size : cutting, crushing, breaking.
  • Change arrangement of particles : particles may move closer together or farther apart.

But in all these cases:

The type and number of particles stay the same, so the mass stays the same.

Everyday Examples

  1. Melting ice
    • Ice in a cup melts to liquid water.
    • If you weigh the cup and ice before, and the cup and water after, the mass is the same.
  1. Evaporation in a closed container
    • Water in a sealed bottle partially evaporates.
    • Some becomes vapor, but none escapes, so the total mass of bottle + liquid + vapor stays constant.
  1. Dissolving salt in water
    • Salt seems to ā€œdisappearā€ when it dissolves.
    • Weighing the closed container before and after shows no change in total mass.

These examples show that even when matter spreads out, becomes invisible, or changes state, its mass is still conserved.

Why Mass Stays the Same

On the particle level:

  • Physical changes rearrange particles but do not change what they are.
  • The same atoms are present before and after the change, just in a new arrangement or spacing.

A helpful picture:
Changing ice to water is like rearranging LEGO bricks from a tower into a flat wall. You still have the same bricks, so the ā€œtotal bricksā€ (mass) is unchanged.

In one sentence: Saying ā€œmass is conserved during a physical changeā€ means that, in a closed system, the total mass of the substance does not change when it changes state, shape, or appearance, because no matter is lost or gainedā€”only rearranged.

TL;DR:
Physical changes can change how something looks or what state itā€™s in, but not how much matter there is. The mass stays constant from start to finish.

Information gathered from public forums or data available on the internet and portrayed here.