A student performs the following procedure:

Procedure

1. Measure 25 grams of an unknown solid.

2. Measure 200 grams of water.

3. Pour the unknown solid and water into beaker, which weighs 50 grams.

4. Stir the solution.

The student records the following observation:

Observation

About half of the unknown solid dissolves and the other half settles to the bottom of the beaker.

Part A:

The student calculated the combined weight of the unknown solid and the water to be 275 grams. Describe the mistake the student made in this calculation.

Part B:

Describe how stirring the solution will affect the total amount of matter in this investigation.