Fourth-fifth Grade
Mixtures and Solutions -Lesson 4
INTENDED CURRICULUM
BIG IDEA: (display in class during the lesson)
Elements and their combinations account for all the varied types of matter around us.
Idaho Standard(s) addressed:
4.S.2.1.2 Describe the physical properties of solids, liquids, and gases. (590.01.b)
4.S.2.1.3 Explain the changes caused by heating and cooling materials. (590.01.c)
5.S.2.1.2 Compare the physical differences among solids, liquids and gases.
CL: D Content Limit: Students will be able to recognize the differences in molecular distance between a solid, a liquid, and a gas, as
well as differences in basic molecular motion.
5.S.2.1.3 Explain the nature of physical change and how it relates to physical properties.
CL: D Content Limit: Students will be able to recognize the change(s) in physical properties that take place when physical changes
occur including ice melting into water and water being heated into steam and the reverse processes .
LESSON CONTENT GOALS
GUIDING QUESTIONS
1) The speed and movement of atoms
increases from solids to liquids to gases.
1) How does the speed and movement of atom
change during physical changes?
2) A saturated solution is one in which no
more solid can be dissolved into the solution.
2) What is a saturated solution?
3) A solute such as salt lowers the freezing
point of a solvent such as water.
3) How does adding a solute affect the
freezing point of a solvent?
4) The mass of a mixture is the same as the
combined masses of its components.
4) How is the mass of a mixture related to the
mass of its components?
Teacher’s notes
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Lesson 4 – Characteristic Properties of Some Solids, Liquids and Gases
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IMPLEMENTED
CURRICULUM
Teacher’s Notes: This lesson will review and build on the basic properties of solids, liquids and
gases learned in the third grade Water unit.
Advanced Preparation and useful science concepts:
(1) Recall that the big idea of this unit is that all of the variety of materials around us comes from just a
few elements. In other words, all matter, from my pillow to the river to people, is composed of
elements like carbon, hydrogen, oxygen and nitrogen. The elements combine to form molecules that
are specific to each thing, and most of the matter that we encounter on a daily basis is actually a
mixture of many different types of molecules.
Another important way that matter varies is in its physical state. Common physical states are solids
liquids and gases. The main thing to know about these states is that molecules do not change from one
state to the next. In other words, a water molecule is H2O (two hydrogen atoms bonded to one oxygen
atom) whether it is ice, water or steam. The only difference from one state to the next is how the H2O
molecules are stuck together. Physical states can be converted back and forth, which is called physical
change. Boiling, melting, condensing and vaporizing are common physical changes.
(2) If you would like, a computer simulation of solids, liquids and gases can be used as a demonstration
during the making meaning conference to review the difference between solids, liquids and gases at the
molecular level. I really like the phet simulation on changes of state:
http://phet.colorado.edu/en/simulation/states-of-matter-basics.
Quick directions:
-
Run the simulation
-
Click on the water on the right hand side of the window, and then you can select solid,
liquid or gas also on the right menu.
-
The simulation displays the speed and connectivity of the molecules in each state.
-
Note that, when a compound is a solid, it is held together by forces (hydrogen bonds)
locking the molecules in place. When you heat and melt the solid, the forces are broken and
the molecules are freer to move and flow as a liquid. Even more energy added breaks all of
the forces and also speeds up the molecules so they fly all over the place as a gas.
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Instead of, or in addition to, the computer demonstration, you can do an interpretive dance: the solid,
liquid and gas dance (SLAG dance):
-Solids: students stand at arms length in place and bounce around but don’t move. This mimics
the forces (the hydrogen bonds in water) holding together molecules in a solid and also that solids are a
fixed shape.
-Liquids: students stay together as a group but slowly mill around close to one another. This
mimics the few forces holding together molecules in a liquid and also that liquids are a fixed volume,
but not a fixed shape.
-Gas: students can bounce around the classroom. Gases have no forces holding them together
and thus their molecules fill all available space.
Note that, in all states, the molecules are the same (H2O is always H2O, whether it is a solid, liquid or
gas) it is just the forces, the hydrogen bonds, holding together the molecules that differ.
Also note that the salt lowers the temperature at which water freezes because it blocks the water from
forming hydrogen bonds. You can include this in your SLAG dance by first having students for
hydrogen bonds in an open space (modeling pure water) and then doing it in a classroom with lots of
tables or desks, which are the sodiums and chlorides. .
(3) In this lesson, students will prepare three different concentrations of solutions of salt and water:
pure water, a ½ spoonful of salt in 25 mL water and 1 spoonful of salt in 25 mL of water. The highest
concentration solution is a saturated salt solution, meaning that it is not possible to dissolve more salt in
the water.
You will need to put the solutions in the freezer for a night. The pure water and the solution with a ½
spoonful of salt in it should freeze while the saturated solution does not. Do test the saltwater
concentrations in your freezer before doing the experiment with your students to make sure that only
the saturated solution does not freeze. If the ½ spoonful concentration also does not freeze, then use
less salt.
(4) If you are feeling excited about changes of state, this is a good time to make slime or jello (making
a semi-solid from a semi-liquid).
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Materials for a group of 4 students:
3 small paper cups that can be put in the freezer
A 25 mL syringe or graduated cylinder
A plastic spoon
About 100 mL water
Stirring sticks
Kosher salt (at least 4 spoonfuls per table)
A tray to put the cups on
Tape for labeling the cups
A balance from the measurement kit (optional)
Also need a freezer with enough space to hold three cups per group.
Brief Lesson Review

Read engaging scenario

Review solids, liquids and gases and then talk about how salt might prevent water from
freezing.

Discuss the problem based on the given scenario and write a focus questions from that
discussion.

Write a prediction.

Students make salt solutions and they are place in the freezer overnight.

Making Meaning Conference: guided discussion on writing claims based on
evidence obtained + SLAG dance or computer demonstation

Claims and Evidence: write claims and evidence focusing on guiding questions

Conclusion: writing a report of findings.

Reflection: writing about types of matter: mixtures, solutions, pure compounds.
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DAY ONE
ENGAGING SCENARIO Teacher says:
“Clearwater Construction is very pleased with your help in identifying their unknown
compound. Now they have another mystery that they would like you to solve: although
it is winter and the temperature is below freezing, the water on the ground at their
construction site remains a liquid. They are very curious to understand why this is
happening and think that it might have something to do with the salt that is on their
construction site. What is the problem here?”
Teacher’s Notes:
Word Wall- Freeze: to change from
a liquid to a solid (opposite of
melting)
Word Wall- Freezing point: the
temperature at which a liquid freezes.
Students are to think what problem(s) they need to solve for this next investigation. Solicit ideas for the
focus questions from the class and display on the board.

Make a selection of the one that will best solve the problems in the scenario.

Students write CLASS FOCUS QUESTION in their notebooks, if it is different from theirs.

Check notebooks and provide feedback when necessary.
FOCUS QUESTION (discuss by groups, display, record in notebooks)
SUGGESTED CLASS FOCUS QUESTIONS
How can we find out if table salt stops water from freezing?
Or
How does the concentration of table salt affect the freezing of a salt solution?
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PREDICTION (discuss by groups, record in notebooks)
Teacher’s Notes
Example of a Prediction:
I think table salt [stops or does not stop] water from freezing because__________________.
For example:
I think table salt stops water from freezing because my parents put salt on the steps when it is icy out.
DAY TWO: PLANNING
Teacher’s Notes and Instructions: Planning how to determine if table
salt stops water from freezing.
Teacher says, “Let’s discuss in our groups to come up with a way of finding out if table salt stops
water from freezing. ”

Allow them time to discuss. Listen in to see if the idea of dissolving salt in water and putting it
in the freezer comes up. Help if needed.
Teacher says, “We need to test pure water and several
Word Wall- Concentration: the
amount of one compound in a
mixture.
concentrations of salt in water to see how the concentration
affects whether the solution freezes or not. We will need to record
our data in a chart. We are going to test three different
Word Wall- Saturated: a solution
with the maximum amount of a
solute dissolved in it.
concentrations of salt in water: pure water, a ½ spoonful in 25
mL water and a saturated solution.”
Lead students on a discussion about saturation. After the
discussion, have them copy the chart into their notebooks. Here
Word Wall- Solubility: the
amount of a solute in a saturated
solution.
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are a few talking points in the discussion:
-
You might have seen a saturated solution when you have made kool-aid. Some of
the sugar doesn’t dissolve and stays at the bottom of the pitcher.
-
You have to stir a mixture for a few minutes to see if it is really saturated. If after a
few minutes of stirring, there is still solid on the bottom of your cup, then the
solution is saturated.
-
Temperature matters to some solutions. For example, a lot of sugar can be added to
hot water but not to cold water. In contrast, the amount of table salt in a saturated
solution doesn’t depend on temperature; it dissolves readily no matter if the water is
cold or hot.
-
Different compounds have differing amounts that can be added to a solution before
the solution becomes saturated, called the compound’s solubility. [note: This is
something that students can test if you have time and inclination: see how much of
the Epsom salts can be dissolved in water, or sugar, and compare it to table salt.
You can measure spoonfuls or the weight of the solid that can be dissolved. This is
also a great opportunity to make rock candy and show students how much sugar
dissolves in hot water compared to cold water. Directions for rock candy are found
on the web.]
Chart 1: Determining if table salt stops water from freezing.
Concentration of table
salt in 25 mL water
1 spoonful
½ spoonful
0 (pure water)
A. Is the solution
saturated?
B. Does the solution
freeze?
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DAY THREE: THE EXPERIMENT

Re-read the class FOCUS QUESTION and review the plan.

Have the following materials available for each group: 3 small paper cups that can be put in the
freezer, a 50 mL syringe or graduated cylinder, a plastic spoon, about 100 mL water, stirring
sticks, kosher salt (at least 4 spoonfuls per group), tray to put the cups on, tape for labeling the
cups

Instruct your students to first label their cups with the amount of salt that they plan to add. Then,
have them add 25 mL water to each cup followed by the salt. They should stir their mixtures.
The ½ spoonful of salt should dissolve, but a bit of the salt should remain on the bottom of the
cup with 1 full spoonful in it. In other words, the 1 spoonful of salt mixture should be saturated.
If it is not saturated, then have the students add a bit more salt. It does take a few minutes of
stirring to get the salt dissolved.

Have students fill in column A in their chart.

Extension exercise: Using the balance from the measurement kit, have students compare the
mass of the two salt solutions. The one that is more concentrated has a greater mass because the
mass of a mixture is equal to the mass of its components. You can also do this as a
demonstration.

Place the cups in your freezer for the night.
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DAY FOUR: MAKING MEANING CONFERENCE (Teacher directed)
Give students an opportunity to observe their cups of pure water and salt water, and to record their
observations in their charts.
1) Share and display findings.
Remember, this is the conferencing stage. It is preferable that students contribute with their ideas. Ask
students to share the information they have written on their chart. Replicate the chart on the board or an
overhead to analyze data. If students need to check the information they wrote on their charts, this is the
right time to do it.
2) Looking for patterns from the data charts:
Guide students to analyze the data by asking the following questions:
 Did the salt dissolve in water? How can you tell?
 Were any of the mixtures saturated? Which one?
 Did the mixtures have the same concentrations?
 (extension) Which solution had the greater mass? (ans. The more concentrated one)
 Did the mixtures have the same physical properties such as:
o Did they have the same appearance?
o Were they solutions?
o Did they freeze?
3) Discuss phase changes and do a computer simulation and/or SLAG dance (see page 2 of this
lesson)
At this point, you will want talk with your students about
phase changes so that they can picture how salt is preventing
the water by interrupting the hydrogen bonds. Use either the
computer simulation or the SLAG dance described on page 2
of this lesson to explain phase changes and the effect of added
salt. Also remind them that they have seen vaporization in the
last two lessons.
Word Wall- Phase change: when a
solid, liquid or gas changes to a
different state of matter.
Freeze: liquid to solid
Melt: solid to liquid
Vaporize: liquid to gas
Condense: gas to liquid
Guide students to understand the computer simulation/SLAG dance by asking the following questions:
 How are solids, liquids and gases different from one another? [ans: they have different amounts
of forces holding them together + the speed of the atoms/compound]
 How are solids, liquids and gases the same? [ans: the identity of the atoms/compounds stays the
same. I.e. H2O stays H2O no matter the state of matter it is in]
 How does salt prevent water from freezing? [ans: it stops the formation of forces holding the
water molecules together]
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4) Guide students in writing CLAIMS from the evidence on the data chart as a group.
Examples
CLAIMS
EVIDENCE
I claim that …..
I claim this because…..
I know that…..
I know this because…..
1.Mixtures with different concentrations have
different physical properties.
1. The saturated solution did not freeze but the lower
concentration solution did freeze.
2. 1 spoonful of salt in 25 mL water is a
saturated solution.
2. Not all of the salt dissolved in the cup with1
spoonful of salt in 25 mL water. Some stayed on the
bottom of the cup.
3. A high concentration of salt is needed to
lower the freezing temperature of water.*
3. Only the saturated solution remained a liquid in
the freezer.
4. Solids have many forces between them and
liquids do not.*
4. The saturated salt solution did not freeze (note:
this one looks like a big jump from the evidence to
the claim, but it is actually how chemists think!)
* It is unlikely that students will come up with these on their own. Instead, you will have to guide
them to it.
CLAIMS AND EVIDENCE (record in notebook)
Teacher says
“You are now going to write 3 claims and evidence statements. I want you to look at the guiding
questions and answer them with a claim based on the evidence. Revisit the class data chart in order to
write your claims. Record them on your notebook.”
Example sentence structures:
I claim that ____________________I claim this because __________________.
I know that__________________. I know this because _________.
Share and discuss claims and evidence with the class
Check and provide feedback
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DAY FIVE: conclusion and reflection
CONCLUSION (record in notebooks)
Ask your students to write a 1-2 paragraph report or business letter to the Clearwater Construction
Company telling them how to solve the problem presented in the engaging scenario.
Check and provide feedback
REFLECTION (record in notebooks)
Students will revisit the “Big Idea” and their results. They write a new investigable question
I wonder if……. What about if………What would happen if………..
that is related to the topic covered and “big idea”.
Check and provide feedback
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ACHIEVED
PROFICENCY FEEDBACK:
CURRICULUM
This guide is:

to be posted on the board/butcher paper so students know what is expected in their
notebooks

to be an evaluation tool for teachers as students work in their notebooks

to be converted into questions as a student self assessment piece
Suggested PROFICIENCY FEEDBACK GUIDE
MIXTURES AND SOLUTONS
LE 4
S
T
Focus Question
 Question written clearly
 Related to the scenario
Prediction
Two


Related to freezing and salt
uses “because”
Us
Data
1 chart
 complete and accurate
 labeled with titles
Claims & Evidence
 3 complete sentences showing
understanding of guided questions
Conclusion
 Grammatically correct
 Describes results
Reflection
 writes one question for further investigation
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ENGAGING SCENARIO LESSON 4
“Clearwater Construction is very pleased
with your help in identifying their unknown
compound. Now they have another mystery
that they would like you to solve: although it
is winter and the temperature is below
freezing, the water on the ground at their
construction site remains a liquid. They are
very curious to understand why this is
happening and think that it might have
something to do with the salt that is on their
construction site. What is the problem
here?”
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Lesson 4 – Characteristic Properties of Some Solids, Liquids and Gases
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Chart 1: Use the first one if you did not measure mass and the second one if you did.
Chart 1: Determining if table salt stops water from freezing.
Concentration
of table salt in
25 mL water
0 (pure water)
Is the solution
saturated?
Does the solution
freeze?
½ spoonful
1 spoonful
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