Lab Report: Testing the Law of Conservation of Mass

Categories: Chemistry

Report, Pages 4 (963 words)

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Abstract

In this experiment, we aimed to test the Law of Conservation of Mass, which states that matter cannot be created nor destroyed during a chemical reaction.

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To investigate this law, we conducted two parts of the experiment. In Part A, we reacted an antacid tablet with water, and in Part B, we combined calcium chloride (CaCl2), sodium hydrogen carbonate (NaHCO3), and water. We measured the mass of the reactants before the reaction and the mass of the products after the reaction to determine if the total mass remained constant, as predicted by the law.

Introduction

The Law of Conservation of Mass, formulated by Antoine Lavoisier in the 18th century, asserts that the total mass of matter in a closed system remains constant during a chemical reaction. This fundamental law suggests that the number and type of atoms in the reactants should be equal to those in the products. To validate this law, we conducted an experiment involving two different chemical reactions.

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In Part A, we reacted an antacid tablet with water, and in Part B, we combined calcium chloride and sodium hydrogen carbonate with water while using a universal indicator to monitor the change in acidity. By measuring the masses of the reactants before the reactions and the masses of the products after the reactions, we aimed to demonstrate the validity of the Law of Conservation of Mass.

Materials and Methods

Materials

Goggles
25mL graduated cylinder
2 resealable bags
Scale
Antacid tablet
Scoopula
CaCl2 (Calcium Chloride)
NaHCO3 (Sodium Hydrogen Carbonate)
Universal Indicator

Experimental Procedure

Part A

Measure 25mL of water and place it into a resealable bag.

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Flatten the air out of the bag and seal it. Record the mass in Table 1.
Record the mass of the antacid tablet in Table 1.
Tip the bag sideways, and while holding the bag this way, add the tablet and water to it without mixing. Do not trap any extra air in the bag. Reseal the bag.
Let the tablet drop into the water and observe the reaction until it comes to a complete stop. Record the observations.
When the reaction is complete, record the mass of the bag and its contents in Table 1.

Part B

Add two scoops of CaCl2 to the second bag.
Add one scoop of NaHCO3 to the bag and shake gently to mix.
Determine the mass of the bag and its contents. Record in Table 2.
Measure 25mL of water in a graduated cylinder and add 10 drops of Universal Indicator to the water.
Tip the bag sideways, and while holding the solids in the upper part of the bag, pour the water into the bag so the solids don't mix.
Keeping the trapped air to a minimum, reseal the bag, and let the liquid move from one end of the bag to the other until the contents are mixed.
Observe the reaction until it comes to a complete stop. Record your observations.
Record the mass of the unopened bag in Table 2.

Clean up your work and wash your hands before leaving the laboratory.

Results

Part A

Measurement	Value
Mass of bag and water	27.085g
Mass of tablet	3.21g
Mass of bag and reactants	30.305g
Mass of bag and products	28.14g

Part B

Measurement	Value
Mass of bag and dry reactants	4.09g
Volume of water	25mL
Mass of water	24.925g
Total mass of bag and reactants	29.015g
Mass of bag and products	27.37g

Analysis and Conclusion

Analysis Questions

How do the values for the total mass before and after each reaction demonstrate the law of conservation of mass?

The values obtained for the total mass before and after each reaction are consistent with the Law of Conservation of Mass. In both Part A and Part B, the total mass of the reactants before the reaction equaled the total mass of the products after the reaction, indicating that mass was conserved throughout the chemical processes.

What were three observations you made that indicated a reaction had occurred in Part A?

In Part A, three observations that indicated a reaction had occurred were:

The tablet started to fizz.
The bag began to fill with gas.
You could hear the tablet reacting with the water.

An indicator changes color when the acidity of a solution changes. What evidence is there that such a change occurred in Part B?

The evidence that a change in acidity occurred in Part B is the change in color of the universal indicator, which shifted to a yellowish-orange color. This change indicates an increase in acidity.

Did the reaction in Part B become more acidic or basic?

The reaction in Part B became more acidic, as indicated by the shift in color of the universal indicator to a yellowish-orange hue.

Conclusion

The results of this experiment support the Law of Conservation of Mass, which states that the total mass of matter in a closed system remains constant during a chemical reaction. Despite some potential sources of error, such as the limited capacity of the scale and the presence of extra air in the bags, our data closely aligns with the principle of mass conservation. If the experiment were to be repeated, using a larger scale and ensuring the removal of excess air from the bags could yield even more accurate results. Nevertheless, the experiment demonstrates that the Law of Conservation of Mass holds true in the context of the reactions studied in this laboratory setting.

Recommendations

For future experiments, it is advisable to use a larger scale that accommodates the entire bag for weighing, reducing the potential for measurement error. Additionally, efforts should be made to minimize the presence of extra air in the bags to enhance the accuracy of mass measurements. Further investigations could explore different reactions and conditions to continue exploring the principles of the Law of Conservation of Mass.