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PURESUBSTANCESandMIXTURESacompletegrade7scienceunit

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PURE SUBSTANCES
AND MIXTURES
ALIGNS WITH THE ONTARIO CURRICULUM
GRADE 7 UNDERSTANDING MATTER AND ENERGY
PURE SUBSTANCES and MIXTURES (GRADE 7)
Thank you for purchasing this grade 7 science unit. This unit is designed to align
with the Ontario science curriculum.
UNIT PLAN
PART ONE:
Introduction- I show a periodic table of the elements (just from Google images) and discuss how
each of the elements are the (very, very tiny) building blocks of everything we can see and feel in
our environment. I have a little bit of Lego (two small pieces and a bigger piece (to model water)–
I use the larger, primary blocks for this) that I snap together to demonstrate that elements
combine together to create larger MOLECULES (and that’s what we’ll be discussing throughout the
unit).
Then we do a bit of role modelling. We stand up and push in our chairs. I ask each student to
pretend to be a water molecule (we usually Google what water molecules look like). I ask the
students to form a solid. We discuss the spacing (shouldn’t be touching but are close; may form
columns and rows; molecules can’t slip around each other). Then I ask the students to “heat up”
by moving three steps forward and three back. If they come close to a desk or another person, I
ask them to go off in a different direction. I stop them once they are separated enough that they
can slip around each other (a liquid) and we discuss the spacing. Finally, I ask the students to
move five steps forward and back, quickly, when we “heat up” again to a gas. Give them enough
time to spread throughout the room. We talk about what is in between molecules (nothing) and
that in a real gas the molecules are much further apart.
We use the SOLIDS, LIQUIDS and GASES handout to consolidate our discussion.
If there is time we do EXPERIMENT 1. You will need CORN STARCH, MEASURING SPOONS,
WATER, MIXING DISH (I use PETRI DISHES). You may have to add cornstarch or water to get the
right consistency (it should be a 2:1 ratio).
PART TWO:
We discuss MASS, VOLUME and WEIGHT and do EXPERIMENT 2. You will need WATER,
GRADUATED CYLINDERS (THAT GO UP TO 400 mL) and SCALES (I use an electronic scale but triplebeam balances work well too). We make a scatter-plot of our results to show the relationship
between volume and mass.
PART THREE:
We fill out the MIXTURES flow chart. We do EXPERIMENT 3. You will need CORN, RICE, IRON
FILINGS, MAGNETS, SIEVES, TWEEZERS, BEAKERS, DISHES, SARAN WRAP. Shake the mixture well
before handing it out to the groups of students. I find that wrapping the magnet in the saran wrap
makes it easy to remove the iron filings. I give the students about 10 minutes to try and separate
the mixture of rice, corn and iron filings. I circulate and can easily find bits of iron filings stuck to
“separated” rice or corn. We discuss how it’s impossible to 100% separate a mechanical mixture
(and that’s just the molecules we can see).
PART 4:
HOW SOLUTIONS FORM. We always role model this first in a cleared-out space in the classroom. I
have some students as “solvent” and some as “solute”. PINNIES are good for this activity (or
nametags). We discuss how the solute is attracted to the solvent equally so is pulled into the
empty spaces. We consolidate our discussion by filling out the handout. I usually do the “SOL”
words handout at this time.
© TEACHING STUFF 2018
PART 5:
We do EXPERIMENT 4. You will need TEST TUBES, MILK, CONTAINERS (I USE BEAKERS), FUNNELS,
FILTER PAPER, VINEGAR, DYE, PEPPER, SALT, WATER, FLOUR. I have test tube brushes as well for
clean-up. We do this experiments in groups. Each member of the group makes 1-2 mixtures. I
call each “mixture” to the back one at a time. To save time I assign each group a mixture to filter,
rather than have each group filter all of the mixtures.
If there is time we work through the SOLUTIONS QUESTIONS.
PART 6:
EXPERIMENT 5. You will need GRADUATED CYLINDERS (100 mL is the perfect size), WATER,
RUBBING ALCOHOL, SALT and SUGAR. If you have smaller graduated cylinders, adjust the amount
of solvent. I do a demonstration before students make their hypothesis. I get two large graduated
cylinders. I fill the first one half-way with marbles. I fill the second one half-way with lentils. I ask
the students: “When I mix them will it fill the cylinder all the way to the top or will it be LESS?”. I
wait until after the experiment to mix the lentils and marbles. It’s an effective way to
demonstrate where the solute goes when it dissolves and why the volume is less.
PART 7:
EXPERIMENTS 6 + 7. You will need SALT, VERY SMALL MEASURING SPOONS, WATER, BEAKERS
(glass works best), TIMER, ICE, and KETTLE. I use the results from experiment 6 as the “room”
temperature result for experiment 7. I leave tap water on the counter for a couple of hours to
acclimatize to room temperature. I do each part (room temperature, cold, hot) with a timer to
control for the amount of stirring. Usually we stir each part for one minute. I pour the kettle and
have the students grip their beakers from the top so their hands don’t come into contact with the
hot glass. We use SAFETY GOGGLES for the hot water. I ask the groups to watch their solutions
carefully – if they are foggy or not totally transparent, I ask them to keep stirring before adding
more solute. I usually collect the results from each group and collate them to reduce the
experimental error (some groups add far too much solute). We graph experiment 7 (and often use
the class results).
PART 8:
EXPERIMENT 8. You will need SCALES (triple beam or electronic), MAGNESIUM SULPHATE
(EPSOM SALTS), SALT, BAKING SODA, SUGAR, SPOON (for stirring and scooping), BEAKERS, and
WATER. It’s very easy to over-saturate so I ask (especially for baking soda and salt) that students
add solute slowly and stir until it is completely clear. If there is any fogginess, they should keep
stirring for a minute. If the solution doesn’t go clear it is saturated. I recommend a “dip stick”
strategy for adding baking soda rather than scooping the solute. Epsom salts and sugar, in
contrast, may take a while to saturate.
PART 9:
SATURATION and SUPERSATURATION
We do another role modelling activity. We clear out a large space and choose 5 students to be the
solvent (spread out in half of the space). I add in the other students (solute) slowly and discuss
terms like unsaturated, dilute, concentration, strong concentration, saturated. Once all the spaces
are filled (5 solute students), “heat up” the solution and have the 10 students fill the whole space.
This makes more space (a hot unsaturated solution). Add in all of the other students (now
saturated). Have the students “cool” by collapsing back into half a room. This is the
supersaturated solution. Discuss how, if disturbed, the solute will clump (and have some of the
solute students clump into “crystals”). I usually “filter” the group by having all of the solvent and
solute molecules go back to their desks, leaving the clumps or crystals. We consolidate by filling in
the handout.
© TEACHING STUFF 2018
PART 10:
EXPERIMENT 9. You will need HOT PLATES or STOVE, GLASS BEAKERS or POTS, SUGAR, EPSOM
SALTS, SALT, BAKING SODA, CORN STARCH, SPOONS, STRING, PENCILS, PAPER CLIPS,
STYROFOAM CUPS, BEAKER TONGS, DYE. Only the corn starch and water mixture will not make
crystals. Make sure each hot solution is saturated. Carefully pour each hot saturated solution
(with tongs if you have them) into a Styrofoam cup, leaving any extra solute behind in the
pot/beaker. I use Styrofoam so the solution cools down more slowly; quick cooling does not
promote good crystal growth. The students attach a string to a paper clip (which acts as a weight)
on one end and to a pencil on the other. The string provides a surface for crystal growth; the
pencil supports the string. I’ll drop the string in each solution and cover with tinfoil. Every couple
of hours, I’ll disturb the solution by pulling the string up and down a few times. The salt and
baking soda crystals form fairly quickly. Epsom salts make a nice crystal after about a day or two.
Sugar can take over a week to form good crystals.
PART 11:
EXPERIMENT 10. You’ll need HEAT SOURCE, FLASK, STOPPER, TUBING, LARGE BEAKER, TEST
TUBE, ICE, WATER, DYE, GLASS PLATES (MICROSCOPE SLIDES), BLACK PAPER OR SURFACE, EYEDROPPER, SALT WATER SOLUTION. I set up the apparatus (like in the distillation apparatus
diagram- see answers for water note below), we make our hypotheses, and then we discuss (and
fill out) the different types of water. We discuss (and fill out) the information on distillation. By
this point the distilled water has collected in the test tube. For the second part of the experiment
we use and eye-dropper to put a drop of salt water on one glass slide, a drop of tap water on a
second slide, and a drop of the distilled water made in part 1 on the third. After doing an open
distillation on your heat source, transfer the glass slides to a dark surface to see the residue (salts
and minerals) that were dissolved in the droplets. I discuss applications of distillation: distilled
water, alcohol concentration, chemical purification and it’s hazards (alcohol/oil products and heat
are a dangerous combination).
PART 12:
Read the article on fractional distillation and answer the questions.
ASSESSMENT
I’ve included a review, a mid-unit test and a final test at the end of this document.
Sometimes, I’ve had students do inquiries on an industrial process (metal ore processing, sugar
processing, waste separation – landfills, recycling) that separates or purifies mixtures. If we don't
have time for a short inquiry, we usually watch a couple of videos from the internet on sugar cane
processing and waste separation.
© TEACHING STUFF 2018
SOLIDS, LIQUIDS AND GASES
Type of
Matter
Molecule
Diagram
PURE SUBSTANCES AND MIXTURES
© TEACHING STUFF 2018
Attraction between Speed of molecules Distance between
molecules
molecules
SOLID
LIQUID
GAS
THE MOLECULE THEORY OF MATTER
1) ALL MATTER…
2) MOLECULES…
3) The more ENERGY molecules have the
4) There are…
they move,
PURE SUBSTANCES AND MIXTURES
EXPERIMENT 1:
SOLID OR LIQUID?
PROBLEM:
Does a mixture of corn starch and water make a solid or a liquid?
HYPOTHESIS:
© TEACHING STUFF 2018
I think that…
MATERIALS:
Beaker, corn starch, water, stir stick
METHOD:
1) Add 2 spoonfuls of corn starch to a dish
2) Add water (1 spoonful) slowly a few drops at a time
3) Stir until mixture does not have “powdery” feel
OBSERVATIONS: Describe the mixture you made:
CONCLUSION:
I was
. We found that…
EXPERIMENT 2:
MASS AND VOLUME OF A SUBSTANCE
PROBLEM:
Does the mass of water DOUBLE as you increase the volume?
HYPOTHESIS: I think that…
MATERIALS:
Beaker, water, balances
METHOD:
1) Measure 100 mL of water in your beaker
2) Take its mass on a balance
3) Repeat for 200 mL, 400 mL,
4) Take the mass of the beaker when it is empty
MASS OF EMPTY BEAKER:
100 mL
OBSERVATIONS:
200 mL
400 mL
Mass of
Beaker + water
Mass of water alone
(subtract mass of beaker
from mass of water +
beaker
RESULTS: Graph the results with a SCATTER PLOT (this is the first graph that you have to hand in)
USE THE PROBLEM as your TITLE!
CONCLUSION:
I was
. We found that…
1) Did the volume exactly double? Why do you think it did/didn’t double exactly?
2) What situations can the volume of a substance increase while it’s mass remains more or less the same?
MASS, VOLUME and WEIGHT
MASS:
VOLUME:
WEIGHT:
© TEACHING STUFF 2018
PURE SUBSTANCES AND MIXTURES
PURE SUBSTANCES AND MIXTURES
SCATTER PLOT:
Graph the data points and, using a ruler, draw a straight line (line of best fit) through them
TITLE:
500
g
400
g
300
g
200
g
100
g
0g
© TEACHING STUFF 2018
100
mL
200
mL
300
mL
400
mL
500
mL
© TEACHING STUFF 2018
EXPERIMENT 3:
PROBLEM:
SEPARATING MECHANICAL MIXTURES
PURE SUBSTANCES AND MIXTURES
Can a MECHANICAL MIXTURE of iron filings, corn and rice be 100% separated?
HYPOTHESIS: I think that…
MATERIALS:
Beakers, corn kernels, rice, iron filings, magnet, sieves, plastic bag, tweezers
METHOD:1)
2)
3)
CONCLUSION:
I was
. We found that…
QUESTIONS:
1) Were you able to separate all the materials completely?
2) What difficulties did you have separating things?
3) A sieve is a kind of filter. Different size sieves are used to filter out different size objects. Can you think
of some examples of sieves/filters or devices that use them? Write the mechanical mixture they
separate out beside them.
1) Filter: pasta colander – Mechanical mixture: pasta and water
2)
3)
4)
5)
6)
© TEACHING STUFF 2018
4) Below is a possible FLOW CHART for the experiment you just did.
EXAMPLE FLOW CHART FOR EXPERIMENT 3:
Corn, rice, iron filings
Legend:
= fully separated
MAGNET
Attracted to magnet
Not attracted to magnet
Iron filings
Corn and rice
SIEVE or PICKING OUT BY HAND
Stopped by sieve
Goes through sieve
Rice
Corn
Make a FLOW CHART underneath here for a mixture of:
BEANS, IRON FILLINGS, WATER, SAND and SALT.
Tools: MAGNET (M), SIEVE with large holes (SLH), SIEVE with small holes(SSH), STOVE and POT (SP)
ORIGINAL MIXTURE:
BEANS, IRON FILLINGS, WATER, SAND and SALT
TOOL:
TOOL:
TOOL:
TOOL:
© TEACHING STUFF 2018
PURE SUBSTANCES AND MIXTURES
HOW DO SOLUTIONS FORM?
STEP 1
Molecule diagram
STEP 2
Molecule diagram
STEP 3
Molecule diagram
© TEACHING STUFF 2018
LEGEND: SOLVENT(
)
SOLUTE (
MOVEMENT)
“SOL” WORDS
PURE SUBSTANCES AND MIXTURES
© TEACHING STUFF 2018
Here are some definitions of some common mixtures words:
1) SOLvent: a substance in a
that does the
It is usually the
.
part of a solution.
2) SOLute: A substance that dissolves (
) into a
It is usually the
.
part of a solution.
3) DisSOLve: When a
breaks up into
and “disappears” into a
.
4) SOLuble: If something
dissolve into something else it is soluble in
that substance (for example
is SOLUBLE in
5) InSOLuble: If something
).
dissolve into something else it is
insoluble (for example
is INSOLUBLE in
).
6) SOLution: is a mixture where the solute is broken up into individual
molecules and is spread throughout the solvent evenly.
7) SOLubility: Solubility is a measurement of the
that can dissolve into a certain
at a
(measured in g/100 mL).
What do all of the “SOL” words have in common (besides having “SOL” in them)?
Fill in the blanks: I mix a
that has sugar as a
and water as a
. I also try to mix in sand but find it is
is very
and has a
. However, the sugar
of 30 g/100 mL in the cold water we
used for the experiment. After stirring it completely
WORD BANK: dissolves, solvent, solubility, solute, insoluble, soluble, solution
.
SOLUTIONS QUESTIONS
PURE SUBSTANCES AND MIXTURES
Use the table below to answer the questions:
SOLUTES
SOLID
tin
LIQUID
mercury
GAS
hydrogen
SOLID
sugar
LIQUID
oil
GAS
carbon dioxide
SOLID
SOLVENT
SOLID
lead
SOLID
gold or
cadmium
SOLID
palladium (a
metal)
LIQUID
water
LIQUID
gasoline
LIQUID
water
GAS
air
scent
molecules
LIQUID
perfume
GAS
air
GAS
GAS
nitrogen (78%)
oxygen (21%)
other gases (1%)
SOLID
Silver (92%)
SOLID
copper (8%)
LIQUID
ethylene
glycol
SOLID
nickel,
chromium and
carbon
LIQUID
Ethanol (1015%)
SOLID
salts and
minerals
SOLID
Zinc
LIQUID
water
SOLID
copper, silver,
nickel, zinc,
and others
SOLID
gold
10)
SOLID
iron
LIQUID
Gasoline (8590%)
LIQUID
water
SOLID
Copper
© TEACHING STUFF 2018
SOLUTION
SOLDER (tin dissolved in lead)
Used to join pieces of metal together when welding
DENTAL FILLINGS (mercury dissolved in cadmium or gold)
Old style dental fillings – new, tooth coloured fillings don’t use metals
such as mercury, gold and cadmium
HYDROGEN STORAGE (hydrogen gas dissolved in palladium)
Used in fuel cells for hydrogen powered engines
MAPLE SAP (sugar dissolved in water)
Any sugary drink is a solution of sugar and water (and other molecules)
OIL dissolved in GASOLINE
Mixture is used in two-stroke engines like lawnmowers weed trimmers.
SOFT DRINKS (carbon dioxide dissolved in water)
The carbon dioxide is dissolved between the water molecules when
under pressure. As soon as you open the drink, the molecules start
coming out of solution. Contains other molecules too: sugar, flavour, etc
SOLID AIR FRESHENER (scent molecules dissolved in air)
The scent molecules evaporate into the air and the “bar” of air
freshener shrinks as it loses molecules
PERFUME dissolved in AIR
The liquid perfume evaporates and the scent molecules dissolve
between the air molecules
AIR (oxygen and other gases dissolved in nitrogen)
Air is a solution of many gases. Most of what we breathe is nitrogen.
Some of the other gases include carbon dioxide, methane, helium,
hydrogen, neon and many others.
STERLING SILVER (copper dissolved into silver)
Pure silver tarnishes quickly when exposed to air. Add a little copper
and it stays “silvery” for longer.
ANTIFREEZE (ethylene glycol dissolved into water)
Ethylene glycol is a type of alcohol that freezes at a low temperature.
STAINLESS STEEL (solutes dissolved into iron)
Iron rusts very quickly when exposed to water or the moisture in air.
Adding nickel, chromium and some carbon from coal stops the rust from
forming.
COMMERCIAL GASOLINE (ethanol dissolved into gasoline)
In many places, ethanol (alcohol) is dissolved into gasoline and sold at
the pumps.
SEA WATER (salts and minerals dissolved in water)
Sea water contains salt (sodium chloride), magnesium, sulphates and
calcium (and many other solutes)
BRASS (zinc dissolved into copper)
Brass is usually used to make decorative metal objects and musical
instruments. Sometimes aluminum and lead are added as well.
GOLD JEWELLERY (solutes dissolved into gold)
Pure gold is too soft to make effective and long-lasting jewellery. Rose
gold has a high amount of copper, yellow gold has copper and zinc
dissolved, and white gold is a solution of gold and various metals: nickel/
manganese/ palladium.
1) Name an example of a solution where a gas is
dissolved into a liquid:
2) Name an example of a solution where a solid is
dissolved into a liquid:
3) Name an example of a solution where a liquid is
dissolved into a gas:
4) Name an example of a solution where a liquid is
dissolved into a liquid:
5) Name an example of a solution where a solid is
dissolved into a solid:
6) Name an example of a solution where a gas is
dissolved into a gas:
7) Name an example of a solution where a solid
dissolves into a gas:
8) Name an example of a solution where a gas
dissolves into a solid:
9) Name an example of a solution where a liquid
dissolves into a solid:
What is the most common solvent on the table?
15) What are three of the solutes in soft drinks?
11)
What is the solvent in STAINLESS STEEL?
16) Which solutions are ALLOYS (an alloy is a metal solution – a
solid in a solid)?
12)
What is the solute in STERLING SILVER?
13)
What are two of the solutes in AIR?
14)
What is the solvent in AIR?
17) According to the table, (look at the %’s) are solutes or
solvents a bigger part of solutions?
MECHANICAL MIXTURES and SOLUTIONS
EXPERIMENT 4:
PURE SUBSTANCES AND MIXTURES
PROBLEM:
Will filter paper be able to separate the following mixtures?
Flour in water, vinegar in water, salt in water, dye in water, milk in vinegar, pepper in water
HYPOTHESIS: Circle or highlight the mixtures in the list below that you think can be separated.
Flour in water
vinegar in water salt in water
dye in water milk in vinegar
pepper in water
MATERIALS:
Test tube rack, flour, vinegar, water, salt, dye, milk, pepper, filter paper, funnels, beakers
METHOD:
1) Fill your test tubes half-way with water except the last one in which you fill with vinegar
2) Add the second substance to the test tube: vinegar/pinch of salt/pinch of pepper/ milk/one drop of
dye/spoonful of flour
3) Mix the pairs of substances together.
Only fill these two
4) Filter one mixture and note if there is any residue left behind.
columns out if the
mixture is a solution!!!
OBSERVATIONS: Fill in the chart as you test the pairs of substances
Was there
Pair of substances
Soluble?
Insoluble?
(Did it dissolve:
did it spread out
or disappear?)
(Were there
chunks of solute?)
YES OR NO
YES OR NO
RESIDUE (stuff)
left behind on
filter?
YES OR NO
Mechanical
Mixture or
Solution?
Write MM or S
Which
substance is
the
Which
substance is
the
solvent?
solute?
This should be
the one being
dissolved into!
This should be
the one that
dissolved!
Flour in water
Vinegar in water
Milk in vinegar
Dye in Water
Salt in Water
Pepper in Water
CONCLUSION: I was
. The following pairs could be separated:
QUESTIONS:
1) What would a good test be to see if a pair of substances form a MECHANICAL MIXTURE or a SOLUTION?
2) Can a SOLUTION be filtered? Why or why not?
© TEACHING STUFF 2018
EXPERIMENT 5:
DOES VOLUME CHANGE IN SOLUTIONS?
PURE SUBSTANCES AND MIXTURES
PROBLEM:
When mixing a solution, does the combined volume go up, down or stay the same
compared with the volume of solute plus solvent separately?
“For example, if I take 20 mL of salt and 100 mL of water, does the resulting solution have a volume of
120 mL (or will the volume be more or less than 120 mL)?”
HYPOTHESIS: I think that, when dissolved, the combined volume will…
MATERIALS:
Graduated cylinders, water, salt, sugar, rubbing alcohol
METHOD:
1) You will make three solutions: Water and salt, water and sugar, and water and rubbing alcohol.
2) Measure carefully 60 mL of water. With a DRY graduated cylinder measure 5 mL
of salt. Mix until dissolved and record new volume.
3) Measure carefully 60 mL of water. With a DRY graduated cylinder measure 5 mL
of sugar. Mix until dissolved and record new volume.
4) Measure carefully 60 mL of water. Measure carefully 5 mL of rubbing alcohol into
another graduated cylinder. Mix and record new volume.
OBSERVATIONS:
Type of SOLUTION
A
Volume of
water
(SOLVENT)
B
Volume of
SOLUTE
C
Add solvent and
solute volumes
(add columns A and B)
D
Actual volume
of solution
when mixed (read
off of graduated
cylinder)
E
Difference between
actual volume and
added volume
(Subtract columns D
from column C)
Water and salt
Water and sugar
Water and alcohol
RESULTS: GRAPH using a BAR GRAPH (make it an integer graph – the bars go down for negative numbers)
This is your 2nd GRAPH that needs to be handed in!
CONCLUSION
I was
. We found that…
3) How does the molecule theory explain your results (think about the spaces between molecules)?
4) Do you think molecules of water, sugar, salt and alcohol all have the same ATTRACTION to water? Why?
© TEACHING STUFF 2018
PURE SUBSTANCES AND MIXTURES
FACTORS THAT AFFECT SOLUBILITY: 1
1DISSOLVING
EXPERIMENT 6:
SOLUBILITY AND STIRRING
PROBLEM: Does STIRRING affect the SPEED of solute that will dissolve in a solvent? (Will more salt dissolve more quickly when it’s stirred?)
HYPOTHESIS: I think that…
MATERIALS:
Graduated cylinders, salt, stirring rod, room temperature water
METHOD:
1) Measure 0.6 mL of salt (using a measuring spoon) into 100 mL of water in a beaker. DO NOT STIR!
2) Add 0.6 mL more if it dissolves. Repeat.
3) Measure 0.6 mL of salt into the second beaker and dissolve it in 100 mL by STIRRING.
4) Add 0.6 mL more if it dissolves and stir.
5) Keep adding more salt in steps of 0.6 mL until it stops dissolving. Record the total amount. Multiply tallies by 0.6 for solubility.
OBSERVATIONS:
Solution
Tally of 0.6 mL amounts added that dissolve
Note: for this experiment we are going to assume that 0.6 mL of salt = 0.6 g of salt
Experimental
SOLUBILITY
in g/100 mL
(add up tallies)
Salt and water
STIRRED
Salt and water
UNSTIRRED
RESULTS: DO NOT GRAPH!
I was
CONCLUSION:
. We found that…
NOTE: Unstirred salt will eventually all dissolve. It just takes a while. In fact – stirring does not affect the amount you can dissolve! Taking into
consideration the molecule theory, why do you think it takes less time when you stir to get all the salt dissolved?
FACTORS THAT AFFECT SOLUBILITY: 2
EXPERIMENT 7: TEMPERATURE AND SOLUBILITY
PROBLEM: Does temperature affect the amount of solute that will dissolve in a solvent? (Will more salt dissolve in cold water or in hot water?)
HYPOTHESIS:
I think that…
MATERIALS:
METHOD:
Kettle, ice water, room temperature water, graduated cylinders, salt
1) Measure 0.6 mL of salt with a measuring spoon and dissolve it in 100 mL of room temperature water by stirring
2) Add 0.6 mL more and stir
3) Keep adding more salt in steps of 0.6 mL until it stops dissolving. Record the total amount of tallies. Multiply number of tallies by 0.6 to find solubility.
4) Repeat for HOT WATER and COLD WATER
OBSERVATIONS:
TEMPERATURE OF
SOLUTION
Tally of 0.6 mL amounts added that dissolve
Note: for this experiment we are going to assume that 0.6 mL of salt = 0.6 g of salt
Experimental
SOLUBILITY
in g/100 mL
(add up tallies)
HOT
ROOM
(use results from experiment 6)
COLD
nd
RESULTS: GRAPH YOUR RESULTS using a bar graph. This is your 2 graph!
CONCLUSION:
I was
. We found that…
© TEACHING STUFF 2018
PURE SUBSTANCES AND MIXTURES
FACTORS THAT AFFECT SOLUBILITY: 3
EXPERIMENT 8:
PROBLEM:
DIFFERENT SOLUTES AND SOLUBILITY
Do different substances have different solubilities? (Will more sugar, salt, alum or baking soda dissolve in water?)
HYPOTHESIS: I think that…
MATERIALS:
Room temperature water, graduated cylinders, stirring rod, sugar, baking soda, electronic scale
METHOD:
1) Half fill a small beaker with solute
2) Take mass of beaker with and without solute
3) Slowly add solute to 100 ml of water until it does not dissolve (SATURATED SOLUTION)
4) Take mass of solute left in small beaker and subtract it from original mass
A
OBSERVATIONS:
TYPE OF
SOLUTION
B
Mass of beaker and
solute after
solution is
saturated
Mass of beaker
and solute
C
Mass of solute
dissolved
(Column A-B)
D
Solubility
Copy the mass from
column C below
SALT
g/100mL
SUGAR
g/100mL
BAKING SODA
g/100mL
MAGNESIUM
SULPHATE
CONCLUSION:
g/100mL
I was
. We found that…
Why do you think one kind of substance is more soluble (dissolves better) than another?
Why do hot solvents dissolve more (and faster) than cool solvents? Use the molecule theory to explain!
**TRY IT AT HOME: What would dissolve more quickly? A – Stirring sugar into cold water or B- leaving the same
amount of sugar in hot water unstirred. Try it at home and let me know your results.
**SOLUBILITY SUMMARY**
FACTORS WHICH AFFECT SPEED of DISSOLVING:
FACTORS WHICH AFFECT AMOUNT THAT WILL DISSOLVE (OVERALL SOLUBILITY):
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CONCENTRATION and SATURATION
LEGEND:
PURE SUBSTANCES AND MIXTURES
SOLVENT
UNSATURATED
SOLUTION
Molecule diagram
SATURATED
SOLUTION
Molecule diagram
CONCENTRATION
Molecule diagram
Molecule diagram
X
SOLUTE
SUPERSATURATION
DESCRIBE WHAT “SUPER SATURATION” MEANS
EXAMPLES:
THE STEPS of SUPERSATURATION
Fill in the step-by-step process of making a super-saturated solution.
STEP 1
Molecule diagram
STEP 2
Molecule diagram
MAKING CRYSTALS FROM a SUPERSATURATED SOLUTION
Molecule diagram
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PURE SUBSTANCES AND MIXTURES
PURE SUBSTANCES AND MIXTURES
WATER
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© TEACHING STUFF 2018
Types of water:
1) Distilled water -
2) Soft water
substance
-
through the process of distillation
-a
solution of water, salts and minerals
- found in
3) Hard water
-a
solution of water, minerals and salts
-found in
4) Salt water
- a very
- found in the
solution of water, minerals and salts
(strong) and
(saturated)
WATER AS A “UNIVERSAL SOLVENT”
-water is often thought of as a “universal solvent” or a solvent that dissolves anything
because _____________________________ . Many different solutes are attracted to it.
-however, it is ________ truly universal because things like rocks and oil do not dissolve in
water (because they are not attracted).
DISTILLATION APPARATUS
PURE SUBSTANCES AND MIXTURES
EXPERIMENT 9: MAKING A SUPERSATURATED SOLUTION AND CRYSTALS
PROBLEM: What solutes will form crystals when you make SUPERSATURATED SOLUTIONS and cool them?
HYPOTHESIS: Highlight the boxes that you think will make crystals.
SUGAR
SALT
BAKING SODA
EPSOM
SALTS
CORN STARCH
MATERIALS:
Hot plates, thermometer, solutes, water, beakers, stirring rods, dye, string, paper clips, pencils, cups, tinfoil
METHOD:
1) Put beaker on hot plate.
2) Carefully stir in small amounts of solute.
3) Do not let the solution boil
4) When you feel solution is supersaturated (no more solute will dissolve) get me (Mr.
Hamblin) to help you transfer the solution to a styrofoam cup to cool
5) You need to place a string with a paper clip into the solution so the crystals have something to grow on.
OBSERVATIONS: Highlight the boxes that made crystals after 24 hours:
SUGAR
SALT
BAKING SODA
EPSOM
SALTS
CORN STARCH
**Some of these solutions might take longer to make really good crystals. I’ll keep them going and you can check on them in a couple of weeks
CONCLUSION:
I was
. We found that…
EXPERIMENT 10:
DISTILLATION
PROBLEM: Part 1: Can a solution of dye and water be separated using distillation?
Part 2: Which kind of solution will leave behind the most RESIDUE: salt, tap or distilled water?
HYPOTHESIS: Part 1: I think that…
Part 2: I think that…
MATERIALS:
Hot plates, slides, salt water, tap water, distilled water, beakers, eye dropper
METHOD: Mr. Hamblin will set up the experiment – you’ll copy the apparatus in your notebook.
OBSERVATIONS:
Part 1: Was there dye in the collection tube?
Part 2: Write 1st beside the type of water that had the most residue
Write 3rd beside the type of water that had the least residue
TAP WATER
CONCLUSION:
I was
© TEACHING STUFF 2018
. We found that…
SALT WATER
DISTILLED WATER
PURE SUBSTANCES AND MIXTURES
.
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PURE SUBSTANCES AND MIXTURES
© TEACHING STUFF 2018
SOLIDS, LIQUIDS AND GASES
Type of
Matter
Molecule
Diagram
PURE SUBSTANCES AND MIXTURES
Attraction between Speed of molecules Distance between
molecules
molecules
SOLID
The most
amount of
attraction
Very slow
(vibrating
back and forth
but “locked”
in place)
Very close
Some
attraction
Slow
Close
Very little
attraction
Very, very fast
Extremely far
apart
LIQUID
GAS
THE MOLECULE THEORY OF MATTER
1) ALL MATTER… is made up of molecules (in solids, liquids and gases) that are
incredibly tiny
2) MOLECULES…are always moving except at -273°C which is called absolute zero
(the coldest possible temperature)
3) The more ENERGY molecules have, the FASTER they move,
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4) There are… no molecules in space (called a vacuum). There is the same
empty space BETWEEN molecules.
MASS, VOLUME and WEIGHT
PURE SUBSTANCES AND MIXTURES
MASS:
• is the amount of matter (solid, liquid,
gas) in an object
• measured in grams (g)
• stays the same everywhere in the
universe
VOLUME:
• is the amount of three-dimensional
space an object takes up
• measured in cubic centimetres (cc) or
litres (1 cc=1 mL)
WEIGHT:
• is the pull of gravity on an object
• measured in Newtons (N)
• weight can change depending on where
the object is in the universe
© TEACHING STUFF 2018
EXPERIMENT 1:
*The ratio of cornstarch to water should be 1 water :2 cornstarch
*If you tap the mixture with force or move it quickly it acts like a solid
*However, because it FLOWS it is a liquid
*Specifically, the mixture is a non-Newtonian fluid.
*There are some great videos online of people running through large vats
of this mixture
*The conclusion should be that the mixture is a liquid
EXPERIMENT 2:
*I’ve used an electronic balance or triple beam balances for this
experiment. The thinner the graduated cylinder the better. If you are
using a beaker for this, your results could be less accurate.
*The mass should more or less double as you increase the amount
(volume). It won’t be exact because of measuring errors.
*In perfect conditions with distilled water at room temperature at sea
level, 100mL of water should equal 100g of mass.
*Hard water, elevation and temperature could all be reasons (as well as
human error) for the lack of “perfect” doubling
*popcorn popping, pouring out pop, and heating something would all be
examples of times when the volume increases without the mass
increasing (in the case of popcorn the mass actually decreases)
*The graph is a good opportunity to introduce or reinforce making a
scatterplot with a trend line (line of best fit)
*There should be three data points
*The line of best fit should start at (0,0) – no volume = no mass – and
continue to the edge
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ANSWERS for flow chart.
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EXPERIMENT 3
*Conclusion: there is no way to 100% separate the mixture (small
amounts or even microscopic amounts of iron filings or other material are
almost impossible to separate out). I tell students that their substances
are 99% pure – it’s usually very easy to find unseparated parts.
*It’s not possible because things stick, we don't have the best tools,
things are small (and emphasize that some are microscopic)
*Examples of filters: air filters, water filters, sink strainers, pool filters,
vacuum bags/filters, oil filter in car
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© TEACHING STUFF 2018
Fill in the blanks: I mix a
that has sugar as a
. I also try to mix in sand but find it is
solvent
is very
solution
soluble
and has a
used for the experiment. After stirring it completely
and water as a
solute
insoluble
. However, the sugar
of 30 g/100mL in the cold water we
solubility
dissolves
.
SOLUTIONS QUESTIONS
PURE SUBSTANCES AND MIXTURES
Use the table below to answer the questions:
SOLUTES
SOLID
tin
LIQUID
mercury
GAS
hydrogen
SOLID
sugar
LIQUID
oil
GAS
carbon dioxide
SOLID
SOLVENT
SOLID
lead
SOLID
gold or
cadmium
SOLID
palladium (a
metal)
LIQUID
water
LIQUID
gasoline
LIQUID
water
GAS
air
scent
molecules
LIQUID
perfume
GAS
air
GAS
GAS
nitrogen (78%)
oxygen (21%)
other gases (1%)
SOLID
Silver (92%)
SOLID
copper (8%)
LIQUID
ethylene
glycol
SOLID
nickel,
chromium and
carbon
LIQUID
Ethanol (1015%)
SOLID
salts and
minerals
SOLID
Zinc
LIQUID
water
SOLID
copper, silver,
nickel, zinc,
and others
SOLID
gold
SOLID
iron
LIQUID
Gasoline (8590%)
LIQUID
water
SOLID
Copper
SOLUTION
SOLDER (tin dissolved in lead)
Used to join pieces of metal together when welding
DENTAL FILLINGS (mercury dissolved in cadmium or gold)
Old style dental fillings – new, tooth coloured fillings don’t use metals
such as mercury, gold and cadmium
HYDROGEN STORAGE (hydrogen gas dissolved in palladium)
Used in fuel cells for hydrogen powered engines
MAPLE SAP (sugar dissolved in water)
Any sugary drink is a solution of sugar and water (and other molecules)
OIL dissolved in GASOLINE
Mixture is used in two-stroke engines like lawnmowers weed trimmers.
SOFT DRINKS (carbon dioxide dissolved in water)
The carbon dioxide is dissolved between the water molecules when
under pressure. As soon as you open the drink, the molecules start
coming out of solution. Contains other molecules too: sugar, flavour, etc
SOLID AIR FRESHENER (scent molecules dissolved in air)
The scent molecules evaporate into the air and the “bar” of air
freshener shrinks as it loses molecules
PERFUME dissolved in AIR
The liquid perfume evaporates and the scent molecules dissolve
between the air molecules
AIR (oxygen and other gases dissolved in nitrogen)
Air is a solution of many gases. Most of what we breathe is nitrogen.
Some of the other gases include carbon dioxide, methane, helium,
hydrogen, neon and many others.
STERLING SILVER (copper dissolved into silver)
Pure silver tarnishes quickly when exposed to air. Add a little copper
and it stays “silvery” for longer.
ANTIFREEZE (ethylene glycol dissolved into water)
Ethylene glycol is a type of alcohol that freezes at a low temperature.
STAINLESS STEEL (solutes dissolved into iron)
Iron rusts very quickly when exposed to water or the moisture in air.
Adding nickel, chromium and some carbon from coal stops the rust from
forming.
COMMERCIAL GASOLINE (ethanol dissolved into gasoline)
In many places, ethanol (alcohol) is dissolved into gasoline and sold at
the pumps.
SEA WATER (salts and minerals dissolved in water)
Sea water contains salt (sodium chloride), magnesium, sulphates and
calcium (and many other solutes)
BRASS (zinc dissolved into copper)
Brass is usually used to make decorative metal objects and musical
instruments. Sometimes aluminum and lead are added as well.
GOLD JEWELLERY (solutes dissolved into gold)
Pure gold is too soft to make effective and long-lasting jewellery. Rose
gold has a high amount of copper, yellow gold has copper and zinc
dissolved, and white gold is a solution of gold and various metals: nickel/
manganese/ palladium.
10) What is the most common solvent on the table?
WATER
11) What is the solvent in STAINLESS STEEL?
IRON
12)What is the solute in STERLING SILVER?
COPPER
13) What are two of the solutes in AIR?
OXYGEN, CARBON DIOXIDE, and
others
14) What is the solvent in AIR?
NITROGEN
© TEACHING STUFF 2018
1) Name an example of a solution where a gas is
dissolved into a liquid:
SOFT DRINKS
2) Name an example of a solution where a solid is
dissolved into a liquid:
MAPLE SAP, SEA
WATER
3) Name an example of a solution where a liquid is
dissolved into a gas:
PERFUME
4) Name an example of a solution where a liquid is
dissolved into a liquid:
OIL in GASOLINE,
GASOLINE, ANTIFREEZE
5) Name an example of a solution where a solid is
dissolved into a solid:
SOLDER, S. SILVER, S.
STEEL, BRASS, GOLD
6) Name an example of a solution where a gas is
dissolved into a gas:
AIR
7) Name an example of a solution where a solid
dissolves into a gas:
AIR FRESHENER
8) Name an example of a solution where a gas
dissolves into a solid:
HYDROGEN STORAGE
9) Name an example of a solution where a liquid
dissolves into a solid:
DENTAL FILLINGS
15) What are three of the solutes in soft drinks?
SUGAR, CARBON DIOXIDE,
FLAVOUR
16) Which solutions are ALLOYS (an alloy is a metal solution
– a solid in a solid)?
SOLDER, S. SILVER, S. STEEL,
BRASS, GOLD JEWELLERY,
DENTAL FILLINGS
17) According to the table, (look at the %’s) are solutes or
solvents a bigger part of solutions?
SOLVENTS
EXPERIMENT 4
EXPERIMENT 5
*The combined volumes should be LESS. Sugar should have the most difference,
followed by salt. The rubbing alcohol has very little difference. I take up the results
and discuss how we may have errors (spills, loss of volume on our hands), and what
a typical result should look like
*Using the molecule theory, students usually come up with:
*some molecules fit into the empty spaces between molecules better than
others
*some molecules are more ATTRACTED to water than others
*In general, we can conclude that sugar is most soluble in water and rubbing alcohol
© TEACHING STUFF 2018
is least soluble
EXPERIMENT 6
*The students should get a couple of spoonfuls dissolved in the stirred but the
original spoonful in the “unstirred” should not have dissolved.
*Stirring increases the SPEED of dissolving
*Why? Stirring lifts the crystals off of the bottom, exposing all sides to the solvent.
We are also moving those empty spaces (in the solvent) over the solute more
quickly.
EXPERIMENT 7
*Hot water should dissolve the most and cold water should dissolve the lease
*Temperature affects SPEED and AMOUNT
EXPERIMENT 8
*Each different solute should have a different solubility in water
ATTRACTION: some molecules are more attracted to water than others.
Hot solvents have more space between their molecules which allows more solute to dissolve. The molecules
are moving faster which moves empty spaces over the solute more quickly.
Almost all students find the COLD/STIRRED combination dissolves more quickly
STIRRING
TEMPERATURE
TEMPERATURE
TYPE of SOLUTE
TYPE of SOLVENT
© TEACHING STUFF 2018
NOTE: another factor is PRESSURE (that’s how carbon dioxide stays
dissolved in pop when it's closed but comes out of solution when the
pressure is released
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© TEACHING STUFF 2018
PURE
HUMAN-MADE
DILUTE
LAKES, RIVERS, RAINWATER
STRONG
GROUND WATER, WELLS
STRONG
OCEAN
SALT LAKES
it can dissolve so many things
NOT
© TEACHING STUFF 2018
EXPERIMENT 9
*Corn starch does NOT make crystals. The other supersatured solutions should.
EXPERIMENT 10
*The dye should be separated out (the water in the test tube should be clear)
*The salt water will have the most residue and the distilled water should have the
least amount (tap water should be somewhere in between)
RAW MATERIAL
SOLUTION
*heat up oil and it turns into a gas
*oil gas rises up in tower
*as oil vapour cools molecules condense
*lighter molecules condense at the top of tower
*heavier molecules condense at the bottom
COOL
LPG (gas)
CHEMICALS (plastics)
GASOLINE (liquid)
JET FUEL, CANDLE WAX
WAX, LUBRICATION OIL
HOT
FUEL OIL
TAR, ASHPHALT
© TEACHING STUFF 2018
REVIEW FOR PURE SUBSTANCES AND MIXTURES
© TEACHING STUFF 2018
1) Draw a MOLECULE DIAGRAM for: (use symbols)
A) PURE substance
B) MECHANICAL MIXTURE
(Heterogeneous)
2)
C) SOLUTION
(Homogeneous)
Show the differences in ATTRACTION, MOLECULE SPACING and MOLECULE SPEED between gases, liquids and solids by filling in this chart:
GAS
LIQUID
SOLID
ATTRACTION
MOLECULE SPACING
MOLECUE SPEED
3)
Explain, using words and diagrams, how a solid dissolves into a liquid:
4)
According to the particle theory, describe the difference between a pure substance and a mixture:
5) Circle the examples of solutions, highlight the pure substances and cross out the mechanical mixtures:
brass
soft drinks (opened)
aluminium
gravel
soft drinks (closed)
sterling silver
concrete
salt water
air
gold rings
solder
distilled water
diamond
© TEACHING STUFF 2018
6) Given two homogeneous clear liquids (solutions), without tasting, how could you determine
which one was distilled water and which one was a salt-water solution?
7) A ______________ is a homogeneous mixture of two or more __________ substances. The substance present in
the greatest amount is called the _______________ while the substance(s) present in lesser amounts is called the
_____________.
8) What do each of the following terms mean?
(a) dilute
(b) concentrated
(c) unsaturated
(d) saturated
(d) supersaturated
9) Give EXAMPLES of SOLUTIONS that are:
DILUTE
CONCENTRATED/SATURATED
SUPER SATURATED
1)
1)
1)
2)
2)
2)
10) In beaker A, 30 g salt are dissolved in 100 mL water, while 15 g salt are dissolved in 65 mL
water in beaker B. Which beaker contains the more concentrated salt solution? Why?
11) Describe how you would make a SUPER SATURATED SOLUTION out of drink crystals.
Pure Substances and Mixtures MID UNIT TEST
© TEACHING STUFF 2018
Name:
Class:
KNOWLEDGE and UNDERSTANDING
MULTIPLE CHOICE: Please circle the best answer:
1)
The following is an example of a PURE SUBSTANCE:
A) diamond
2)
C) tap water
D) pulpy orange juice
B) gas
C) liquid
D) solution
B) iron
C) carbon
D) chromium
B) heirioslation
C) mechanical mixture
D) pure substance
B) solution
C) liquid
D) gas
C) liquid
D) gas
In which state are molecules moving most QUICKLY?
A) solid
9)
B) trail mix
Which state has molecules that are, more or less, locked in place (they can’t flow around each other)?
A) solid
8)
D) pop with chunks of ice
A SIEVE could be used to separate a:
A) solution
7)
C) clear grape juice
Steel is a mixture that has this metal as a solvent:
A) copper
6)
B) water
According to the Molecule Theory of Matter, which state has molecules that are the CLOSEST together?
A) solid
5)
D) air
Circle the SOLUTION
A) white sugar
4)
C) trail mix
Circle the MECHANICAL MIXTURE
A) clear apple juice
3)
25
B) apple juice
B) solution
9
In which state are molecules of a pure substance most ATTRACTED to each other?
A) solid
B) solution
C) liquid
D) gas
TRUE AND FALSE: please write the whole word “TRUE” or the whole word “FALSE”
10) Solvent molecules fit in-between solute molecules when they dissolve
11) A solution can be filtered to separate one part from another
12) Water and a small amount of sugar should form a solution after stirring
13) If I take a volume of solvent and mix it with a volume of solute, the combined volume
of the solution I make will be the same as the separate volumes from before added together
14) Solutions form because of the attraction between the solute and the solvent
15) Molecules in a gaseous state are really far apart and don’t have a lot of attraction
6
MATCH UP: Write the letter of the definition in the blank beside the word that matches it
PURE SUBSTANCE
A) A substance which dissolves “into” another substance
SOLUTION
B) The EXACT AMOUNT of a solute that will dissolve
into an amount of solvent to make a saturated solution at a
certain temperature
SOLUBILITY
C) A substance that is made up of all the same type of
molecules
SOLUTE
D) A mixture made up of different types of molecules that are
clumped together
INSOLUBLE
E) When a solute breaks apart into a solvent
MECHANICAL MIXTURE
F) A substance that does the dissolving in a solution
(solutes dissolve into this substance)
SOLUBLE
G) A combination of different pure substances put together
SOLVENT
H) When one substance can dissolve into another substance
DISSOLVING
I) When one substance cannot dissolve into another substance
MIXTURE
J) A mixture in which the molecules of the different
substances are evenly spread out.
10
© TEACHING STUFF 2018
PURE SUBSTANCES AND MIXTURES TEST
© TEACHING STUFF 2018
Name:
THINKING/COMMUNICATION
Class:
40
=
%
1) A chemist gets 6g of Brand X sweetener to dissolve into 50mL of water to make a saturated solution.
She is able to dissolve 10g of Brand Q artificial sweetener in 100mL of water to make a saturated
solution. She concludes Brand Q is more soluble in water.
Do you agree? Explain why or why not. Use MATH/CALCULATIONS to prove your point!
Show all of your thinking!
5
COMMUNICATION
2) Explain what distillation is and describe some real-world uses and products created by distillation.
10
THINKING/COMMUNICATION/APPLICATION: Use
an extra piece of paper if needed.
© TEACHING STUFF 2018
2) A) Explain, using WORDS and MOLECULE diagrams, how ice-tea drink crystals (a solid) dissolve
into water (a liquid). In other words, explain how a solution is formed.
10
B) Explain how (using words and/or a flow chart) you would make ice-tea syrup (a supersaturated
solution) out of the room temperature ice-tea solution (contains: water, sugar, tea, lemon juice)
you made in part A.
Make MOLECULE DIAGRAMS to show what's going on with the molecules at each stage of your
process.
You have extra tea bags, lemons, sugar, a fridge, a stove and pot, containers, filter paper and
magnets if you need them.
10
**Use these words: UNSATURATED, SATURATED, CONCENTRATED, DILUTE, SOLUTION,
SUPERSATURATED and MECHANICAL MIXTURE in your answer.**
C) Explain, in detail, how you could make “ice-tea” crystals (that you could add to water) out of the
ice tea syrup you made in part B.
5
REVIEW FOR PURE SUBSTANCES AND MIXTURES
1) Draw a MOLUCULE DIAGRAM for: (use symbols)
A) PURE substance
B) MECHANICAL MIXTURE
(Heterogeneous)
C) SOLUTION
(Homogeneous)
2) Show the differences in ATTRACTION, MOLECULE SPACING and MOLECULE SPEED between gases, liquids and solids by filling in this chart:
GAS
LIQUID
SOLID
ATTRACTION
SOME
A LOT
SOME SPACE
VERY LITTLE SPACE
SLOW
VIBRATING BUT NOT MOVING
VERY LITTLE
MOLECULE SPACING
HUGE AMOUNT OF SPACE
MOLECUE SPEED
VERY VERY FAST
3) Explain, using words and diagrams, how a solid dissolves into a liquid:
*diagrams (see “How solutions form”)
*solid solute is more attracted to liquid solvent than it is to itself
*solute molecule breaks off of solid crystal and moves into the empty space between solvent
molecules
*because solute is equally attracted to all solvent molecules, it is “pulled” from empty space to
empty space
*once all molecules are broken up, the mixture is a solution
4) According to the particle theory, describe the difference between a pure substance and a mixture:
A PURE SUBSTANCE HAS ONLY ONE TYPE OF MOLECULE IN IT. A MIXTURE HAS TWO OR MORE DIFFERENT TYPES OF
MOLECULES IN IT.
5) Circle the examples of solutions, highlight the pure substances and cross out the mechanical mixtures:
brass
soft drinks (opened)
aluminium
gravel
soft drinks (closed)
sterling silver
concrete
salt water
air
gold rings
solder
distilled water
diamond
© TEACHING STUFF 2018
6) Given two homogeneous clear liquids (solutions), without tasting, how could you determine
which one was distilled water and which one was a salt-water solution?
*Do an open distillation. Evaporate the water away and the minerals will be left behind
*No minerals = distilled water
*Minerals = salt-water
7) A SOLUTION is a homogeneous mixture of two or more PURE substances. The substance present in the greatest
amount is called the SOLVENT while the substance(s) present in lesser amounts is called the SOLUTE
8) What do each of the following terms mean?
(a) dilute – very small amount of solute compared to solvent. “Weak” concentration
(b) concentrated – a large amount of solute compared to solvent. “Strong” concentration
(c) unsaturated – more solute can be dissolved. Lots of empty space left over
(d) saturated – all empty spaces in solvent are filled. No more solute can dissolve
(e) Supersaturated – more solute is dissolved than is natural. A hot, saturated solution is cooled
down – if undisturbed, will stay in unstable supersaturated state
9) Give EXAMPLES of SOLUTIONS that are:
DILUTE
CONCENTRATED/SATURATED
SUPER SATURATED
1) TAP WATER
1) OCEAN WATER
1) CORN SYRUP
2) WATERY DRINK
2) SUGARY DRINK
2)MAPLE SYRUP/HONEY
10) In beaker A, 30 g salt are dissolved in 100 mL water, while 15 g salt are dissolved in 65 mL
water in beaker B. Which beaker contains the more concentrated salt solution? Why?
Beaker A is a 3:10 ratio (or 30%). Beaker B is a 1:5 ratio (or 20%). Beaker A is more
concentrated.
A second way of comparing is to double Beaker B to 30 g of salt and 130 mL of water – clearly
more dilute.
11) Describe how you would make a SUPER SATURATED SOLUTION out of drink crystals.
*heat up the water
*dissolve as much drink crystal as you can (make a hot saturated solution)
*cool down the solution, being careful not to disturb it
© TEACHING STUFF 2018
Pure Substances and Mixtures MID UNIT TEST
7
ANSWERS
KNOWLEDGE and UNDERSTANDING
MULTIPLE CHOICE: Please circle the best answer:
1) The following is an example of a PURE SUBSTANCE:
A) diamond
25
B) apple juice
C) trail mix
D) air
B) water
C) clear grape juice
D) pop with chunks of ice
B) trail mix
C) tap water
D) pulpy orange juice
2) Circle the MECHANICAL MIXTURE
A) clear apple juice
3) Circle the SOLUTION
A) white sugar
4) According to the Molecule Theory of Matter, which state has molecules that are the CLOSEST together?
A) solid
B) gas
C) liquid
D) solution
C) carbon
D) chromium
C) mechanical mixture
D) pure substance
5) Steel is a mixture that has this metal as a solvent:
A) copper
B) iron
6) A SIEVE could be used to separate a:
A) solution
B) heirioslation
7) Which state has molecules that are, more or less, locked in place (they can’t flow around each other)?
A) solid
B) solution
C) liquid
D) gas
C) liquid
D) gas
8) In which state are molecules moving most QUICKLY?
A) solid
B) solution
9
9) In which state are molecules of a pure substance most ATTRACTED to each other?
A) solid
B) solution
C) liquid
D) gas
TRUE AND FALSE: please write the whole word “TRUE” or the whole word “FALSE”
10) Solvent molecules fit in-between solute molecules when they dissolve
FALSE (other way around)
11) A solution can be filtered to separate one part from another
FALSE
12) Water and a small amount of sugar should form a solution after stirring
TRUE
13) If I take a volume of solvent and mix it with a volume of solute, the combined volume
of the solution I make will be the same as the separate volumes from before added together
FALSE (LESS)
14) Solutions form because of the attraction between the solute and the solvent
TRUE
15) Molecules in a gaseous state are really far apart and don’t have a lot of attraction
TRUE
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MATCH UP: Write the letter of the definition in the blank beside the word that matches it
PURE SUBSTANCE
C
A) A substance which dissolves “into” another substance
SOLUTION
J
B) The EXACT AMOUNT of a solute that will dissolve
into an amount of solvent to make a saturated solution at a
certain temperature
SOLUBILITY
B
C) A substance that is made up of all the same type of
molecules
SOLUTE
A
D) A mixture made up of different types of molecules that are
clumped together
INSOLUBLE
I
E) When a solute breaks apart into a solvent
MECHANICAL MIXTURE
D
F) A substance that does the dissolving in a solution
(solutes dissolve into this substance)
SOLUBLE
H
G) A combination of different pure substances put together
SOLVENT
F
H) When one substance can dissolve into another substance
DISSOLVING
E
I) When one substance cannot dissolve into another substance
MIXTURE
G
J) A mixture in which the molecules of the different
substances are evenly spread out.
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10
PURE SUBSTANCES AND MIXTURES Test Term One
ANSWERS
40
THINKING/COMMUNICATION
=
%
1) A chemist gets 6g of Brand X sweetener to dissolve into 50mL of water to make a saturated solution.
She is able to dissolve 10g of Brand Q artificial sweetener in 100mL of water to make a saturated solution.
She concludes Brand Q is more soluble in water.
Do you agree? Explain why or why not. Use MATH/CALCULATIONS to prove your point!
Show all of your thinking!
The student should NOT agree!
BRAND X times 2: 6/50 = 12/100 (or concentration is 0.12 or 12%) so is higher than brand Q
There are a lot of ways a student can show this.
5 marks for a very clear answer that shows, correctly, calculations
4 marks for a clear, correct answer – communication could be a bit better
3 marks for math but no explanation
2 marks – incorrect but attempted math or explanation
1 mark – incorrect – little shown to explain thinking
COMMUNICATION
2) Explain what distillation is and describe some real-world uses and products created by distillation.
I break it down like this but it’s up to you
5 marks for a well communicated explanation of what distillation is
2 marks for a labelled diagram of the distillation apparatus
3 marks for discussing other examples of distillation (fractional distillation, distilled water, alcohol).
© TEACHING STUFF 2018
THINKING/COMMUNICATION/APPLICATION: Use
an extra piece of paper if needed.
3) A) Explain, using WORDS and MOLECULE diagrams, how ice-tea drink crystals (a solid) dissolve
into water (a liquid). In other words, explain how a solution is formed.
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B) Explain how (using words and/or a flow chart) you would make ice-tea syrup (a supersaturated
solution) out of the room temperature ice-tea solution (contains: water, sugar, tea, lemon juice)
you made in part A.
Make MOLECULE DIAGRAMS to show what's going on with the molecules at each stage of your
process.
You have extra tea bags, lemons, sugar, a fridge, a stove and pot, containers, filter paper and
magnets if you need them.
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**Use these words: UNSATURATED, SATURATED, CONCENTRATED, DILUTE, SOLUTION,
SUPERSATURATED and MECHANICAL MIXTURE in your answer.**
C) Explain, in detail, how you could make “ice-tea” crystals (that you could add to water) out of the
ice tea syrup you made in part B.
AGAIN – I’ll break it down but it’s up to you
A) 10 marks for a perfect explanation and diagrams (from “How Solutions Form”)
B) 2 marks for molecule diagrams – like from note on supersaturation
8 marks for explanation – perfect answer includes, correctly, each of the bolded words
and explains clearly that you would HEAT ice tea solution, add more sugar, tea and
lemons until it’s SATURATED. Filter out solids (tea, lemons). COOL in fridge until
supersaturated.
C) 4 marks for explaining that you need to disturb syrup from part B and that crystals will
on a string or other surface
1 mark for explaining that you need to scrape crystals off of string or filter them out of
© TEACHING STUFF 2018
the syrup.
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