Teacher Candidate: Caroline Ferguson
Activity: Percent Composition
Time: 75 minutes
Content
Specific Expectation:
D3 .1 explain the law of definite proportions
D2.2 conduct an inquiry to calculate the percentage composition of a compound
Previous Homework
Warm-Up Activity
Materials Needed
Read p. 198-204
- Bite the Bubble Activity - Grade 11 Chemistry Textbook
(McGraw-Hill Ryerson)
- Bite the Bubble Activity worksheet
(below)
- Percent composition worksheet with
answers (below)
Activity Descriptions:
Bite the Bubble Activity
- Working with partners, students find the mass of different types of gums (including
sugar-free) before and after chewing them
- Use class data to find the average percent composition of sugar each type of gum.
- Be sure to include gums with high and low sugar contents (and others with gel-like
sugary filling)
- Discuss sources of error – ie mass of saliva introduced.
Consolidation
Introduction
Ministry Strand: Quantities in Chemical Reactions
Associate Teacher: Marcel Dufresne
Unit Day #: 7
Percent Composition Calculations
- Model how to calculate percent composition of C2H6 (the first example in the
worksheet below)
- Have students work in groups to complete the worksheet
- Call for volunteers to write solutions on the board, and explain what they did.
Consolidation Activity
Assessment and Evaluation Homework
- What is the difference
- Teacher assesses students’
- Finish worksheet
between the percentage of knowledge by walking
sugar that we calculated
around the class as they
- p. 205 #1, 4, 5, (try 7); extra
from the Bite the Bubble
complete their activity.
practice: p. 201 #1-3, p. 204 #5, 7
activity (ans: it was a
- Students demonstrate their
mass percent) vs. the
knowledge when they
percent composition
calculations in the
worksheet (ans: it was an
atom or mole percent)
CHM3U
Unit 3 - Quantities in Chemical Reactions
Lesson 7 – Calculation of Percentage Composition
A. Bite the Bubble: A Chemistry Mini-Lab
Objective: To calculate the percentage of sugar in various types of gum.
Procedure:
1.
2.
3.
4.
5.
6.
7.
Each lab partner should unwrap one piece of gum and place it in the cup. Measure the
mass of the cup and the pieces of gum. Record.
Subtract the mass of the cup to get the mass of the gum. Record.
Each lab member should retrieve a piece of gum and chew vigorously for 10-15
minutes.
Collect the gum back in the cup and measure the mass of the chewed gum and the cup.
Subtract the mass of the cup to get the mass of the chewed gum. Record.
Subtract the mass of the chewed gum from the mass of the un-chewed gum to get the
mass of the sugar that was removed.
Calculate the percentage of sugar in the gum. Show your calculations!
*All measurements should be made to the nearest tenth of a gram.
Group #
Type of Gum
Percentage of Sugar
B. Percentage Composition Calculations
Calculate the percentage composition of each of the following compounds. Show all your work.
a. C2H6
b. FeCl2
c. FeCl3
d. C2H4O2
e. CaCO3
f. NaOH
g. CaCl2 . 2H2O
h. (NH4)3PO4
i. Ag(NH3)2Cl
j. C17H15N3O2Cl
Teacher’s Answers:
1.
(a)
% C = 79.85 %
% H = 20.15 %
(b)
% Fe = 44.04 %
% Cl = 55.94 %
(c)
% Fe = 34.43 %
% Cl = 65.57 %
(d)
% C = 40.00 %
% H = 6.73 %
% O = 53.28 %
(e)
% Ca = 40.04 %
% C = 12.00 %
% O = 47.96 %
(f)
% Na = 57.48 %
% O = 40.00 %
% H = 2.53 %
(g)
% Ca = 27.26 %
% Cl = 48.22 %
% H = 2.75 %
% O = 21.77 %
(h)
% N = 28.19 %
% H = 8.13 %
% P = 20.77 %
% O = 42.92 %
(i)
% Ag = 60.81 %
% N = 15.79 %
% H = 3.42 %
% Cl = 19.98 %
(j)
% C = 62.10 %
% H = 4.61 %
% N = 12.78 %
% O = 9.73 %
% Cl = 10.78 %