Law Of Conservation Lab 3s212i

Anthony Adduci Chemistry Period 4

Introduction: The law of conservation of mass as defined is that the mass of a closed system will remain constant, regardless of the process acting inside the system. An equivalent statement is that matter cannot be created or destroyed, although it may be rearranged. This implies that for any chemical process in a closed system, the mass of reactants must equal the mass of the products. Therefore this lab was to the law of conservation of mass using vinegar and baking soda. In this lab, students work in small groups of two to complete a laboratory exercise related to conservation of mass. Using vinegar, baking soda, and a 250ml beaker, students measured the amount of gas that was released or in escaped in an open system (not sealed). Students then seal the vinegar and baking soda in a plastic bag and mix the substances. A gas is formed which will inflate the bag. The mass of the sealed bag will then be determined in order to ascertain if there has been any change in the mass of the reactants and product before and after the reaction took place. As the law of conservation states, matter cannot be created or destroyed, although it may be rearranged. As of this statement it was concluded that the mass of a closed system will remain constant, regardless of the process acting inside the system. Being left with a simple question, will the mass of the final reaction (gas escaped) be greater in a closed system or in an open system?

Materials and Procedure: • •

• • • • • •

Baking soda (NaHCO3) 15 grams Vinegar (CH2COOH) 300 ml 400 ml beaker 100 ml graduated cylinder Balance 150 ml beakers (2) Twist ties (2) Plastic bag

Anthony Adduci Chemistry Period 4

Part one: For part 1, weight about 4-5g of baking soda by using a scale. After done weighing, transfer the baking soda into a beaker. Then measure about 100 ml of vinegar and place it in and beaker, record volume. Mass both of these beakers together using a scale and record the initial mass to the nearest 0.01g. Take the beakers off the balance and carefully add the vinegar to the baking soda. When the reaction is complete, mass again both beakers to find the final mass to the nearest 0.01g. Record the mass and calculate any change in mass.

Part 2: Gather materials such as plastic bag, twist ties, beakers and balance. First weigh about 45g of baking soda and about 50ml of vinegar. First add baking soda into bag and tightly close with a twist tie, then add the vinegar and tightly close the bag again. Note* you should have “2 layers”, first being baking soda and second being vinegar. Then take bag to balance and record to the nearest 0.01g. Then remove bottom twist tie and observe reaction. After reaction is complete weigh the bag once more and record again to the nearest 0.01.

Data & Analysis:

Volume

Mass before

Mass after

Gas escaped

Part one

100ml

289.8g

287.1g

2.7g

Part two

50ml

57.44g

56.37g

1.08g

Table one shows the results, before and after each reaction of part one and part two. Note* g = grams and ml = milliliters

Sample Calculations: Part 1

289.8 – 287.1 = 2.7g of gas escaped

Part 2 

57.44 – 56.36 = 1.08g of gas escaped

Anthony Adduci Chemistry Period 4

Conclusion: The law of conservation of mass indicates that mass cannot be created nor destroyed. This means the total mass of reactants in a chemical reaction will equal the total mass of the products. If a gas is produced during a reaction, which mass is often forgotten when calculating the final mass because students are unable to see the gas. For this reason, plastic bags were to be used to collect the gas. In an open system, it was obvious that more gas would be expected to escape because there was no top over the beaker. Rather in a closed system, it was predicted that more gas would remain before and after the reaction because it was trapped inside the plastic bag, held by twist ties. The law of conservation of mass was violated in part one because the starting mass of the reactant was 289.8g while after the reaction was 287.1. Therefore you can examine that about 2.7g of gas escaped in an open system. This compared to a closed system, where only 1.08g of gas escaped. The starting mass was 57.44 and after the reaction it weighed 56.36. Therefore the law of conservation of mass was proved in a closed system because; the mass of a closed system will remain constant, regardless of the process acting inside the system.