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Questioning
Hypothesizing
Planning
4.2 Inquiry Investigation
Conducting
Recording
Analyzing
Communicating
Comparing Salt Water and Fresh Water
Just how different are salt water and fresh water?
You can examine their physical characteristics,
such as density and buoyancy. Density is the
mass of a substance for one unit of its volume.
For example, 1 cm3 of distilled water has a mass
of 1 g, so the density of distilled water is written
as 1 g/cm3. Buoyancy is the upward push on an
object by a fluid.
Materials
Question
How is salt water different from fresh water?
Hypothesis
Salt water has a greater force
of buoyancy, a greater density,
and more residue left after
evaporation than fresh water
does.
Never drink or even
taste anything from
a science class.
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apron
safety goggles
salt water (3.5% saline solution)
fresh water
distilled water
microscope slides
eyedropper
desk lamp
microscope
100-mL graduated cylinder
triple-beam balance or scale
beakers
drinking straw
food colouring
30-cm wooden dowel
Experimental Design
You will compare the
properties of salt water
and fresh water listed in
the hypothesis.
1 Copy Table 1 into your
notebook.
Procedure
2 Obtain samples of fresh
water and salt water from
your teacher.
• Examine the appearance
and odour of both water
samples.
(a) Record these observations
in your table.
3 Measure 3 drops of
fresh water on a clean
microscope slide. Rinse
the eyedropper in distilled
water. Measure 3 drops of
salt water on another
slide.
• Place the slides under a
desk lamp to evaporate
the water.
• Using a microscope,
5A examine any residue
on the slides.
(a) Record your
observations.
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Unit 4
4 Measure the mass of an
empty graduated cylinder.
(a)Record the mass.
• Pour 100 mL of fresh
water in the cylinder and
measure the mass of both.
(b)Record the mass of the
cylinder and water.
(c)Calculate and record
the mass of the water.
• Rinse the cylinder with
distilled water. Repeat
step 4 using salt water.
SKILLS HANDBOOK: 5A Using the Microscope
Table 1
Comparing Salt Water and Fresh Water
Fresh Water
Salt Water
A. Appearance (include colour)
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B. Odour
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C. Residue after evaporation
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D. Density
mass of empty graduated cylinder
mass of graduated cylinder and
100 mL of water
Making Connections
1. Fresh water from rivers mixes
with salt water when the river
reaches the sea. Write a
paragraph predicting whether
the fresh water mixes
completely with, floats above,
or sinks below the ocean water.
Support your prediction using
evidence from this investigation.
mass of 100 mL of water
density of water sample (per 100 mL)
Exploring
density (per 1 mL)
2. How would increasing the
amount of salt in salt water
2E affect buoyancy? Design an
investigation to answer this
question.
E. Buoyancy
depth to which dowel sank
float test: fresh water over salt water
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float test: salt water over fresh water
Reflecting
3. When conducting today’s
investigation, did your group
share the recording and
physical work equally? How
might you work differently in
upcoming investigations?
9D
How could you use your knowledge
of what happens when salt water
evaporates to help you with the safe
drinking water challenge?
Analysis
7 Analyze your results by
answering the following
questions.
5 Place a wooden dowel
in a graduated cylinder
containing 100 mL
of fresh water.
• Use the markings on
the graduated cylinder
to measure the depth
at which the bottom
of the dowel floats.
(a)Record the depth
in your table.
• Repeat for salt water.
6 Add 1 drop of food
colouring to 50 mL of
fresh water.
• Half fill a beaker with
uncoloured salt water.
• Use a straw to transfer
the coloured water to the
surface of the salt water.
Repeat several times.
(a)Record your
observations.
• Repeat the above process,
this time transferring
coloured salt water onto
uncoloured fresh water.
2E Designing an Inquiry Investigation 9D Working Together
(a) How does salt water
residue differ from fresh
water residue? What
appears to make up
most of the residues?
(b)Explain any difference in
the density of the samples.
(c) How have you
demonstrated that salt
water exerts a greater
force of buoyancy than
fresh water? Explain using
your results.
(d)How do the densities of salt
water and fresh water help
explain the difference in
their buoyancy?
Water Systems
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