Question

which procedure could be used to demonstrate that matter is conserved during a physical change?

This is the correct answer: Find the mass of a piece of ice. Let the ice melt. Find the mass of the liquid water.

explain to me why its the correct answer.

Answer 1

Why this procedure shows conservation of matter

1. A melting ice cube is a physical change, not a chemical one.
- The substance before and after is the same chemical species: H2O. Melting only changes the arrangement and energy of the molecules (solid → liquid), not their identity.

2. Mass is the right quantity to check.
- Conservation of matter means the amount of matter (mass) stays the same. Volume changes when ice melts (ice is less dense than liquid water), so measuring volume could be misleading. Mass does not change if no matter enters or leaves the system.

3. The measurement compares the same matter before and after the change.
- If you weigh a piece of ice on a balance, let it melt, and then weigh the liquid water, any equality of the two masses shows no matter was lost or gained during the change. That directly demonstrates conservation of matter for that process.

Important experimental notes (so the result is valid)
- Prevent loss or addition of matter to the system (use a sealed or covered container, or melt the ice in a dish on the balance and keep everything on the balance so no water spills). If water evaporates or spills, mass can change and give a false result.
- Use the same container (tare the container first) so you compare only the ice/water mass.
- Use a sufficiently precise balance to detect any real differences.

In short: melting ice keeps the same H2O molecules but changes their state; weighing before and after (with the system closed) shows the mass is unchanged, which is direct evidence that matter is conserved in that physical change.