Conservation of Mass Lab

To determine whether the mass of a substance decreases, increases or stays the same in a chemical reaction.
If a chemical reaction occurs in a substance, will the mass of the substance remain the same or will the mass change?
Materials Required
Alka Seltzer tablet (half a tablet)
1 Balloon
Erlenmeyer flask
Spot Plate
150ml of Water
Goggles, gloves and an apron was put on.
The Erlenmeyer flask was filled with 150ml of water.
The Alka Seltzer tablet was inserted inside the balloon.
The opening of the balloon was placed over the rim of the Erlenmeyer flask.
The Erlenmeyer flask was set on the weighing scale, then it was removed after the initial mass was recorded.
The balloon was raised upward, over the Erlenmeyer flask allowing the Alka Seltzer tablet to fall straight into the Erlenmeyer flask.
When the Alka Seltzer tablet and the water, together start to react, the Erlenmeyer flask was placed on the weighing scale.
All materials were measured and data was recorded.


Total mass of Reactants and apparatus before reaction (g)
Predicted mass after the reaction
Qualitative observation
Measured mass after reaction (g)
Qualitative observations of products after reaction
Tablet: Solid, white, powdery and dull
Water: Wet, odorless and colorless.
Tablet dissolved in water and bubbles were formed. Water became translucent.

Analyze and Evaluate

There was a 0.2g difference between the products and the reactants. This may have been caused by the balloon not being secured to the rim of the Erlenmeyer flask, allowing the gas from the reaction to evaporate or escape therefore lowering the mass of the product.
The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. According to the law of conservation of mass, the mass of the products in a chemical reaction must equal the mass of the reactants. Thus proving that the experiment did confirm the Law of Conservation of Mass because both the measurement that were taken before and after the experiment were almost the same. (Difference - 0.2g)

Apply and Extend
24231608763000Citric Acid + Sodium Bicarbonate Water + Carbon Dioxide + Sodium Citrate
183642090805(C6H8O7) + Na (HCO3) H2O + CO2 + C6H5Na3O7

Sources of Error

During the experiment there were a few areas in which error could have possibly occurred. For Example, the amount of time taken for the Alka Seltzer tablet and the water to react before being put on the weighing scale, could have resulted in a different mass being recorded. This is because there was not a specific time limit designated to observe the reaction between the Alka Seltzer and the water. Therefore, if the substances in the Erlenmeyer flask was left for too long, or too little while it was reacting, it would have resulted in a different mass, due to the gases made by the chemical reaction releasing into the air, or by heat gained during the reaction. Likewise, the size of the Alka Seltzer tablet may have further caused error in the experiment because of the size of the tablet varying, resulting in the reaction to also vary. This would have directly affected the qualitative results that were written about the products, after the reaction because a larger reaction may have caused a different or more pronounced qualitative feature than a small reaction.


There are a few improvements or adjustment that can be made to the experiment in order for the results to become more accurate or specific. For example, a time limit can be put on how long it takes for the content to react, before weighing and collecting qualitative data. The procedure states that the mass was measured before and after the reacting taking place however, the amount of time taken to record the mass after and before the reaction varied between each group, resulting in a difference of both the quantitative and the qualitative results. Therefore, for the next time the experiment is done, a specific amount of time should be designated in order for the substance to begin reacting before weighing and collecting data, this will allow a more accurate result for both the qualitative and quantitative portions of the data. Likewise, each station should consist of the same size of Alka Seltzer tablets. The size of the Alka Seltzer tablet