Reactants and Products Virtual Lab
Is mass conserved during a chemical reaction?
Background
Chemical reactions are processes that change chemical substances into other chemical
substances. One of the key questions about chemical reactions is whether or not mass is
conserved during the course of a reaction. In other words, will the mass of the product of a
chemical reaction be equal to the mass of the reactants, or is mass destroyed or lost in the
course of a reaction?
Setup
Open the activity called “Reactants and Products Virtual Lab” in your digital course.
http://72.32.119.67/pearson_vl/topic7_1/
Note: You will have opportunities to save data at different stages of this activity. You can
download data for offline purposes, such as answering questions in the Analyze and Interpret
Data section of this worksheet. When you save data as an image, give it a title that matches the
given experiment or the specific part of the virtual lab activity.
Procedure
Follow the onscreen instructions and record information below as you run through the
experiments. You will be able to go back to previous parts or “reload” a part by clicking the
buttons to the right of the Investigation tab. Likewise, if you go backward you can click the
forward button to return to a later part.
Part 1
□ 1.
□ 2.
When you mixed the potassium iodide and lead nitrate in the jar, was there any evidence
of a chemical reaction?
Save an image of the data table from the potassium iodide and lead nitrate reaction and
paste it below, or draw the table.
Reactants and Products Virtual Lab • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.
□ 3.
How does the sum of the masses of the reactants compare to the mass of the products?
What does this indicate about the conservation of mass?
□ 4. Write the balanced chemical reaction between potassium iodide and lead nitrate.
Part 2
□ 5.
Save a copy of the data table from the baking-soda-and-vinegar reaction and paste it
below, or draw the table.
□ 6.
Was mass conserved in this reaction? Explain.
□ 7.
Write the balanced chemical reaction between baking soda and vinegar.
Reactants and Products Virtual Lab • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.
Part 3
□ 8. Save a copy of the data table from the baking-soda-and-vinegar reaction that featured the
use of the balloon and paste it below, or draw the table.
□ 9.
When you repeated the reaction and used the balloon to “close” the system, what did you
notice about the mass of the reactants and the mass of the final products? Was mass
conserved? Explain.
Analyze and Interpret Data
1. Plan Your Investigation Using real lab equipment, how could you attempt the cesium-andwater reaction depicted in this virtual lab to study whether mass is conserved in that
reaction?
2. Connect to Society Where do you think the law of conservation of mass is used in the real
world, and why is it useful?
Reactants and Products Virtual Lab • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.
TE Support
Focus on NGSS This lab builds toward mastery of MS-PS1-5. Students will apply the following
practices, ideas, and concepts in this activity.
Science and Engineering Practices
Connect to the Core Idea
Crosscutting Concept
Collect data about the performance of
a proposed object, tool, process, or
system under a range of conditions.
Substances react chemically in
characteristic ways. In a chemical
process, the atoms that make up the
original substances are regrouped into
different molecules, and these new
substances have different properties
from those of the reactants.
Macroscopic patterns are related to
the nature of microscopic and atomiclevel structures.
Purpose Students will be able to explain the law of conservation of mass and how it applies to
chemical reactions.
Class Time 45 minutes
Expected Outcome Students will master the following concepts:
1. Mass is conserved in chemical reactions.
2. Conservation of mass is not always easy to detect, especially if the system is open or the
reaction isn’t controllable.
TE Annotations: Procedure
1. Yes, there was evidence that a chemical reaction occurred. The color of the mixed reactants
changed from white to yellow. A color change indicates a chemical reaction.
2. Saved data table:
3. The sum of the masses of the reactants is equal to the mass of the product, indicating that
mass was conserved.
4. 2KI(s) + Pb(NO3)2(s) -> 2KNO3(s) + PbI2(s)
Note: Some students may not denote the solid states of the reactants and products.
Reactants and Products Virtual Lab • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.
5. Saved data table:
6. Students may answer that mass was not conserved, because 17.3 grams is less than the
sum of the reactants. Others may correctly infer that the carbon dioxide produced by the
reaction was lost from the tube and therefore its mass was not measured.
7. NaHCO3(s) + CH3COOH(aq) -> CH3COONa(aq) + CO2(g)
Note: Some students may not denote the states of the reactants or products.
8. Saved data table:
9. Yes, mass was conserved. The mass of the products equaled the mass of the reactants. The
balloon trapped the carbon dioxide gas that had escaped earlier in the open version of the
experiment.
TE Annotations: Analyze and Interpret Data
1. You could set up the reaction in a sealed, extremely sturdy reaction vessel from which mass
could not escape. In that case I would need only to record the mass before and after the
reaction.
2. Answers should mention fields or industries in which the appropriate masses or volumes of
chemical reactants must be carefully brought together to produce products of certain
composition and mass and/or volume.
Reactants and Products Virtual Lab • Copyright © by Pearson Education, Inc., or its affiliates. All Rights Reserved.