Inquiry
INVESTIGATION
5-A
Skill Check
Initiating and Planning
✓
Performing and Recording
✓
Analyzing and Interpreting
✓
Communicating
Materials
• 1 dozen dried kidney beans
(or another type of large bean)
• 1 dozen dried chick peas
(or another type of bean of similar
size)
• 1 dozen dried lentils (or another
type of bean of similar size)
• small piece of copper wire, Cu(s)
• 10 mL of sodium chloride (table
salt), NaCl(s)
• 10 mL distilled water, H2O()
• 50 mL beaker
• balance
• graduated cylinder
Exploring Conversions
between Mass and Particles
In this investigation, you will work with two units of quantity: the dozen and
the mole. You will practise converting a dozen into individual items, and vice
versa. You might ask, “How is working with a dozen useful in chemistry?” In
the second part of this investigation, you will apply the skills you learned while
working with a dozen to determine quantities of different sample substances.
Pre-Lab Questions
1. How would you convert 10 dozen into a number of items? Describe the
steps you would follow, and perform the calculation.
2. How would you convert 10 moles into a number of particles? Describe the
steps you would follow, and perform the calculation.
3. Read the Procedure and then explain why it is important that you use the
same 50 mL beaker in Part 1 and Part 2 of the investigation?
4. How would you determine the amount in moles of a sample, if you are
given only its mass?
Questions
How can you use units of quantity, such as a dozen and a mole, to count
small objects and particles and to determine mass? How can you use mass to
determine quantities of a substance and number of particles?
Procedure
Part 1: Counting and Measuring the Mass of Beans
1. Read steps 2 to 5 in this Procedure, and create a table to record your results.
2. Count out one dozen of one type of bean.
3. Measure the mass of the 50 mL beaker. Record your result.
4. Fill the beaker with the dozen beans. Measure the mass of the beans and
beaker. Record your result.
5. Repeat steps 2 to 5 for each type of bean you have been given.
Part 2: Measuring the Mass of Chemicals
6. Read steps 7 to 11, and create a table to record your results.
7. Measure the mass of the sample of copper given to you by your teacher.
Record your result.
8. Determine the molar mass of copper from the periodic table. Record this
value in your table.
9. You have already measured the mass of the 50 mL beaker in Part 1. Add
10 mL of sodium chloride to the beaker. Measure the mass of the sodium
chloride and the beaker. Record your result.
10. Determine the molar mass of sodium chloride from the periodic table.
Record this value in your table.
11. Repeat steps 9 and 10 using distilled water instead of sodium chloride.
244 MHR • Unit 3 Quantities in Chemical Reactions
Analyze and Interpret
Part 1
1. For each type of bean, calculate the mass of the dozen
beans in the beaker.
2. From the net mass found in step 1, calculate the
average mass of a single bean for each type of bean.
3. For each type of bean, calculate the number of beans in
3.5 dozen. Then calculate the mass of 3.5 dozen beans.
4. For each type of bean, calculate how many dozen beans
you would have if you had 25.0 g of beans. How many
individual beans would you have?
Part 2
5. Use the mass and the molar mass of each substance
you measured to calculate the amount in moles of
each sample. Remember to calculate the net mass for
the sodium chloride and water samples.
6. Determine the number of atoms of copper, molecules
of water, and formula units of sodium chloride in the
samples you were given.
7. Calculate the mass of 1 mol of each substance.
8. Calculate the mass of one particle (atom of copper,
molecule of water, and formula unit of sodium
chloride) of each substance.
9. Calculate the number of particles in 3.0 mol of each
substance.
10. Calculate the mass of 5.0 mol of each substance.
11. Calculate the amount in moles of each substance
in 100 g of the substance.
Conclude and Communicate
12. What general strategy or formula could you use to
convert a dozen items to individual items, and vice
versa?
13. What general strategy or formula could you use to
convert a number of dozen items to the mass of the
items, and vice versa?
14. What general strategy or formula could you use to
convert the mass of a substance to the mass of one
particle of the substance?
15. What general strategy or formula could you use to
convert the mass of a substance to the amount in moles
of the substance?
16. What general strategy or formula could you use to
convert the amount of a substance to the number of
particles of the substance?
17. Compare the strategies or formulas you used in Part 1
with the strategies or formulas you used in Part 2.
How are they similar?
Extend Further
18. INQUIRY Design an investigation that will enable
you to answer the following question: What amount
in moles of calcium carbonate, CaCO3(s), is in one
tablet of a given calcium supplement? Assume that the
supplement contains only calcium carbonate.
19. RESEARCH Research how knowledge of chemical
quantities is important in the education, training, and
work of environmental chemists.
Chapter 5 The Mole: A Chemist’s Counter • MHR 245
Inquiry
INVESTIGATION
5-B
Skill Check
Initiating and Planning
✓
Performing and Recording
✓
Analyzing and Interpreting
✓
Communicating
Safety Precautions
• Tie back loose hair and clothing.
• Do not touch the lit candle.
• Be careful not to spill any molten
wax on your hands.
Materials
• paraffin wax candle (tea light)
• wooden splints
Using the Mole for Measuring
and Counting Particles
The mole is used to group large numbers of particles (atoms, molecules, ions,
and formula units) of a substance. Chemists can use the mole to determine how
many particles of a substance they are working with. In this investigation, you
will use the mole concept to practise measuring and counting atoms, molecules,
and other particles of different substances.
Pre-Lab Questions
1. List safety precautions you should take when working with a candle in
a laboratory.
2. Write a plan to figure out the amount of candle wax that burns over
a period of time and the rate at which it burns.
3. Describe the correct method for measuring a crystalline solid, such as
table salt or table sugar, on a balance.
• water
• sodium chloride (table salt),
NaCl(s)
• sucrose (table sugar), C12H22O11(s)
• weighing paper
• paper
• wax crayon
• balance
• clock or timer
• small paper clip
• beaker
• 10 mL graduated cylinder
• medicine dropper
• 50 mL graduated cylinder
• ruler
Question
What are some methods for measuring and counting the number of atoms,
molecules, formula units, and ions in samples of different chemicals?
Procedure
1. Read through this Procedure, and create a table you can use to record your
results for each step.
2. Measure the mass of a candle. Light the candle, and burn the paraffin wax
for 10 min. Put out the candle, and let it sit for 4 min to allow the melted
wax to solidify. Measure the mass of the candle again.
3. Measure the mass of a paper clip. Try floating the paper clip on water in
a beaker. Hold the paper clip horizontally (flat). Very carefully, lower the
paper clip onto the surface of the water. The paper clip should float.
4. Measure the mass of a 10 mL graduated cylinder. Using a dropper full of
water, count the number of drops of water you need to get 1 mL of water in
the cylinder. Measure the mass of the water and the cylinder.
5. a. Calculate the mass of 0.10 mol of sodium chloride. Using weighing
paper, measure the mass on a balance, and place it in a 50 mL graduated
cylinder. Measure and record the volume of the salt. Return the salt to
the weighing paper.
b. Calculate the mass of 0.10 mol of sucrose. Using weighing paper, measure
the mass, and place it in the 50 mL graduated cylinder. Measure and
record the volume of the sugar. Return the sugar to the weighing paper.
6. a. Draw a 10 cm by 10 cm square on a piece of paper. Measure the mass of
your favourite colour of wax crayon.
b. Colour in the entire square as completely as possible with the wax
crayon. Measure the mass of the crayon again.
c. Repeat the process with a 20 cm by 20 cm square on a piece of paper.
246 MHR • Unit 3 Quantities in Chemical Reactions
Analyze and Interpret
1. Refer to your results from Procedure step 2 to answer
this question.
a. Calculate the number of wax molecules that
burned. Assume that the formula for paraffin wax
is C25H52(s).
b. Calculate the number of carbon atoms that burned.
2. Refer to your results from Procedure step 3 to answer
this question: How many atoms of iron is the water
holding up? Assume that the paper clip is pure iron.
3. Refer to your results from Procedure step 4 to answer
this question.
a. What is the mass of 1 mL of water?
b. How many water molecules are in 1 mL of water?
c. How many hydrogen atoms are in one drop of water?
d. Calculate the volume of one mole of water.
4. Refer to your results from Procedure step 5 to answer
this question.
a. Compare the volumes of the 0.10 mol samples of table
salt and table sugar, and account for any differences.
b. How many sodium and chloride ions are in the
salt sample?
c. How many oxygen atoms are in the sugar sample?
5. Refer to your results from Procedure step 6 to answer
this question. Assume that the wax crayon, like the
candle, is paraffin wax. Based on the mass of wax
crayon used, calculate the number of molecules of wax
in the 10 cm by 10 cm square and the 20 cm by 20 cm
square. Compare the difference in the areas of the two
squares with the difference in the masses of the wax.
How do they compare?
Conclude and Communicate
6. When burning a candle like the one in this
investigation, how long would it take to burn 1 mol
of paraffin wax?
7. In terms of the wax crayon, what would the
dimensions of a square coloured on a page have to be
to use an entire mole of wax?
8. Calculate the mass of one mole of water. Then, using
your calculations for the volume of one mole of water,
calculate the density of water at room temperature in
grams per millilitre (g/mL). Check a reference source
to see if this value is reasonable.
Extend Further
9. INQUIRY Design an investigation to determine the
number of particles (molecules or formula units) of
chalk it would take to write your name. First, research
the main chemical that makes up chalk. Perform your
investigation after your teacher approves it.
10. RESEARCH In this investigation, you assumed that the
formula for the paraffin wax you used was C25H52(s).
Research the different formulas for paraffin wax.
How did the formula you used affect your results?
Why was it important to make an assumption about
the formula in order to calculate your results?
Chapter 5 The Mole: A Chemist’s Counter • MHR 247