Grade 10 Science
Name: _____________________________________
Inquiry: ____ / 36
Communication: ____ / 10
Law of Conservation of Mass
Part A – Measuring Mass in Chemical Changes
Purpose: Does the total mass change as the reactants undergo chemical change to form the products?
Hypothesis: The mass of the products will be ______________________________ the mass of the reactants.
Materials and Method: see page 228 - 229 of text, but use FeCl3(aq) instead of Fe(NO3)3(aq). Also use a 125 mL
erlenmeyer flask and a small test tube.
Observations:
Qualitative (3 marks)
Reactant
Description of Reactant
Description of Products Upon
Mixing Reactants
iron (III) chloride
sodium hydroxide
Quantitative: Write down the CLASS AVERAGE here: (1 mark)
Average Mass of Reactants, Test
Tube, Flask and Stopper (g)
Average Mass of Products, Test
Tube, Flask and Stopper (g)
Analysis: Answer the following questions using full sentences. The number of marks allotted per question are
in brackets.
1) Answer the question asked in the Purpose. Was your hypothesis correct?
(2)
2) What observation indicates that a chemical change took place in this experiment? (1)
3) What are the formulas for the reactants in this lab? (iron (III) chloride and sodium hydroxide) (2)
4) The two reactants combine in a double displacement reaction to produce two products: one of them is
iron (III) hydroxide , (Fe(OH)3), the orange-red solid. What is the name and formula of the second product, the
combination of sodium and chlorine? (2)
5) Write the skeleton equation for the reaction (including state subscripts) and then balance it.
(3)
6) Justify the Law of Conservation of Mass by stating the number and type of each atom in the reactants and in
the products of your balanced equation.
(2)
7) A solid has a mass of 35 g. When it is mixed with a solution, a chemical reaction occurs. If the final total
mass of products is 85 g, what was the mass of the solution? Show all your work for full marks. (2)
Part B – Finding the Missing Mass
Purpose: Does the Law of Conservation of Mass apply to a chemical reaction in which a gas is produced in an
open container?
Hypothesis: The mass of the products will be ____________________________ the mass of the reactants.
Materials: test tube, 250 mL beaker, hydrochloric acid solution, 25 mL graduated cylinder, sodium bicarbonate
(baking soda), scoopula, balance
Method:
1) Use the graduated cylinder to measure 10 to 15 mL of hydrochloric acid into the test tube.
2) Put two heaping scoopulas full of sodium bicarbonate into the beaker. Place the test tube into the beaker
and then measure the mass of the beaker, the test tube and the two reactants. Describe both reactants.
3) Get a flaming splint ready using a lit Bunsen burner, in order to do a flaming splint test on the reaction.
4) Slowly pour the acid into the beaker containing the sodium bicarbonate. Record your observations.
5) Place the test tube back into the beaker, and measure the mass of the beaker, test tube and products.
Observations:
Qualitative (3 marks)
Reactant
Description of Reactant
Description of Products Upon
Mixing Reactants
when mixed:
hydrochloric acid
flaming splint:
sodium bicarbonate
Quantitative: (1 mark)
Write you OWN mass
here:
Mass of reactants, test tube and
beaker (g)
Mass of products, test tube and
beaker (g)
Analysis: Answer the following questions using full sentences.
1) Answer the question asked in the Purpose. Explain. (2)
2) What might account for any difference in mass you observed in this reaction? (1)
3) What evidence do you have that a chemical reaction occurred in this experiment? (1)
4) Why does cake rise when it is baked? How do you think the mass of the cake would compare to the original
mass of the ingredients in the recipe? Explain. (2)
5) Sarah carried out an experiment to examine the burning of magnesium. She
Mass of magnesium (g) 3.0
determined the mass of a piece of magnesium ribbon. Then she burned it in air,
Mass of product (g)
5.0
being careful to collect all the pieces of white powdery solid that was produced.
Finally, she determined the mass of the product.
6a) Write a word equation for the reaction. There are two reactants and one product. (2)
b) Write a balanced skeleton equation for the reaction (including state subscripts). (4)
c) Classify the type of reaction. (1)
d) Using the observation table created in the experiment and the Law of Conservation of Mass, explain Sarah’s
results. (1)