Proving the Law of Conservation of Mass

A close-up photo of a graduated cylinder and a conical flask that each contain some blue liquid, and are on a white table with some test tubes laying nearby.

Proving the Law of Conservation of Mass
A Scientific Investigation

Conducted by DJ Hadoken

1. Aim – To prove the Law of Conservation of Mass.

2. Hypothesis – I believe that the mass will remain the same before and after the chemical reaction.

3. Background – The Law of Conservation of Mass states that matter is neither created nor destroyed in any process.

1. Find the mass of the empty Erlenmeyer flask, test tube, and rubber stopper. Record.

2. Measure 20 mL of copper sulfate solution using the graduated cylinder. Pour into the Erlenmeyer flask.

3. Measure 10 mL of sodium hydroxide solution and pour into test tube. CAUTION: Sodium hydroxide is extremely caustic. Use precaution.

4. Place test tube with sodium hydroxide into flask containing copper sulfate. Be careful not to mix the two solutions. Stopper the flask and record observations on the two solutions.

5. Find mass of flask, test tube, rubber stopper, and the two solutions. Record.

6. Tip flask so the solution in test mixes with the solution in the flask. Be careful of spills.

7. Record any evidence of reaction in data table.

8. Find the mass of flask, test tube, rubber stopper, and products of the reaction. Record this mass in data table


Mass of Flask, Test Tube, and Stopper (g)
Empty Flask 147.9 g
Before Mixing 178.5 g
After Mixing 178.5 g

Appearance of Solutions
Copper Sulfate Looked blue.
Sodium Hydroxide Clear, like water.
After reaction Looked crystallized, blue.
Color remained, liquidy light blue.

1. The mass of the two reactants was 30.6 g.

2. The mass of the products was also 30.6 g.

Analysis and Conclusions:
1. The change I observed that indicated that a reaction took place was after the two liquids mixed. A crystallized substance was produced.

2. The mass of the two solutions was the same as that of the product of the reaction.

3. With respects to the Law of Conservation of Mass: mass was indeed conserved in this reaction.

4. It was a chemical reaction, because it involved two solutions being mixed, creating a new substance.


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