Major Concepts Activity 40
• The concentration of a solution is expressed in
terms of parts of solute to parts of solution.
• Parts per million (ppm) are used to express
concentrations with very small solute to
solution ratios
• Concentrations can be expressed as parts per
___, fractions, ratios, %
Activity 45 Follow-up
Precipitation and Filtration
Results
• Test 1: Not all contaminant has precipitated
because there is blue solution remaining around
the edges of the precipitate.
• Test 2: Not all contaminant has precipitated, but
more than Test 1.
• Test 3: Not all contaminant has precipitated, but
more than Test 2.
• Test 4: All of the contaminant has precipitated
because there is no blue solution remaining;
there is only solid blue precipitate present.
Activity 45 Analysis
1. What was the contaminant in this activity?
– Copper chloride
2. What evidence indicates that a chemical
reaction occurred when you mixed solutions
of sodium carbonate and copper chloride?
– Color change
– Appearance of new solid
– Bubbles (release of gas)
3. a. You added sodium carbonate solution to the copper
chloride solution. Where do you think the solid that
appeared came from?
– A chemical reaction between the sodium carbonate and
copper chloride
– It’s called a precipitate
b. Why does the substance get trapped by the
filter?
– It is an undissolved solid and is too large to pass through the
filter
c. What property(ies) does (do) all solid precipitates that
form and settle to the bottom when two solutions are
mixed have?
– All solid precipitates are slightly soluble
– They appear as solids and do not remain dissolved
– Since the solids settle to the bottom, they must be more
dense than the surrounding liquid.
4. Describe two ways the control in Test 1 helped
you analyze the data.
– Used as a comparison to the other 3 tests
– Helped determine if all the contaminant had
precipitated out
– Helped in comparison after filtering and the
procedure on the filtrate to make sure that
contaminant was detected in it
5. a. Did precipitation work for removing the
contaminant from the water? Explain, using
evidence from the investigation.
– Precipitation worked for removing the
contaminant in Test 4
– The filtrate looked clear and colorless and there
was a lot of precipitate on the filter
– Test 1 had the most remaining contaminant
because the filtrate was very blue and there was
no precipitate in the filter paper
– Tests 2 and 3 were in between
5. b. Did your procedure for testing the presence of
contaminant in the filtrate work well? How did
you know how well it worked?
– Yes, a precipitate formed when sodium carbonate was
added
– No, no precipitate formed when sodium carbonate
was added
5. c. If your procedure did not work well, think of
at least one way you could improve it.
– Add more drops of sodium carbonate
– Do an ammonia test
– Do both tests
6. How could the procedure in this investigation
be useful for purifying wastewater?
– Chemicals that react with the dissolved
substances to form a precipitate can be added to
the waste water to form a precipitate
– The precipitate can be filtered out
7. Copper is a metal. Look at the Periodic Table
of Element, and list two other elements that
you think this procedure would work well for
if they were contaminants.
– Any metal near copper including cobalt, iron,
nickel, silver, etc.
Activity 43
Title: Municipal Water
Treatment
Read C-67
Problem: How do community water districts
ensure that the water they provide is safe?
Hypothesis/Initial Thoughts:
Stopping to Think (STT)
• Do #1, 2c, 4a and 4b only
• Do Analysis 1-5
• The book is available on my web page if you do
not finish