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Grade 7 Science

Unit 3: Mixtures and

Solutions

Chapter 8: Some substances dissolve to form

solutions faster and more easily than others.

Name: __________________________

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Making Solutions

When you mix two substances they form a ____________________

Solutions have two parts

For each situation identify the solute and the solvent:

Situation Solute Solvent

A. Brass is used to

make many

objects. Brass is a

solution of zinc

metal in a copper

metal

B. Hydrogen

peroxide is used

to disinfect cuts.

Hydrogen

peroxide is a

solution of 3%

hydrogen and

97% water.

C. Dental amalgam is

a metal that is

used to fill

cavities. It is a

solution of

mercury in tin.

The substance that

dissolves

(found in less

amounts)

ex: sugar

The substance in

which the solute

dissolves.

(found in the

greatest amount)

Ex :water

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D. Deicing fluid is a

cleaner used to

clean car and

truck windshields.

It is made up of a

solution of

propylene glycol

in water.

Dissolving

Definition:

Dissolve

________________________________________________________________________

________________________________________________________________________

How are substances soluble?

According to the particle theory of matter, “there are _____________forces between the

particles”. In order to dissolve the _______________must be more strongly attracted to

the solvent than to themselves. This is means the solute is ____________in the solvent.

If something is ABLE to dissolve then it is _________________________.

Ex: __________________________________________________________________

How are substances insoluble?

If the particles of the ____________ are more attracted to their own particles than the

solvent particles, ______________does not occur. The solute is said to be __________

in that solvent.

If something is UNABLE to dissolve then it is _______________________.

Ex: __________________________________________________________________

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Soluble or Insoluble?

Solvent or not??

Some materials are good _________________ for some solutes but not for others.

For example, ____________________________________________________________

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Complete Activity 8 -1C Page 259

“Does it Dissolve?”

Different states of matter of Solutes and solvents.

Solvents and solutes can be different states of matter.

Fill in the state of matter for each solute and solvent in the given solution

Solution Solute Solvent State of solute State of solvent

Soda water Carbon dioxide Water GAS LIQUID

Vinegar Acetic acid Water LIQUID LIQUID

Salt water salt Water SOLID LIQUID

Brass zinc Copper SOLID SOLID

Concentration (p. 262)

The two cups below each had hot water with a tea bag sitting in them. The time

below the cup indicates how long the tea bag has been in the cup.

Definition: _A solution that has a __ Definition: A solution that contains a small

large amount of dissolved solute _ amount of dissolved solute

for a certain amount of solvent. for a certain amount of solvent.

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Directions:

1. Supposing these were clear cups, use a brown lead to color how dark you think

the tea would be in each cup.

2. Write the statement dilute solution or concentrated solution under the cup you

think it describes.

3. Write the definition for each statement in the space provided

Describing Concentration

The quantity of ___solute___ that is dissolved in a certain quantity of the _solvent__.

Concentration can be described two ways:

Qualitative or Quantitative?

Statement Qualitative Quantitative

Food coloring made the

water blue. √

Adding 3 mL of food

coloring turned 250 mL of

water blue.

√

The water became warmer. √

The water’s temperature

increased by 5 degree

Celsius.

√

We needed just over a

dozen floor tiles for our

model room.

√

QuaNtitatively

“With Numbers”

such as units of grams

per litre (g/L)

Qualitatively

“With words”

like dilute and

concentrated

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We needed 14 floor tiles

for our model room.

√

The liquid boiled in 5 min.

√

The liquid took only a few

minutes to boil. √

The mass of this solid is 5g

more than that one.

√

This solid is heavier than

that one. √

He drinks eight glasses of

water each day. √

???

He drinks 2L of water each

day.

√

Question:

If you were a diabetic and had to watch you sugar intake, would you want to know the

concentration of a drink qualitatively or quantitatively? Why?

I would want to know the quantitative concentration of sugar in a drink because I

would need to know an exact amount so I know how much insulin to take, or how

many carbohydrates I can eat.

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1. Convert each of the following from g/mL to g/L.

a) 10 g/ 100 mL = _______________________

b) 52 g/ 100 mL = _______________________

c) 65 g/ 100 mL = _______________________

d) 100g/ 100 mL = _______________________

e) 137g/ 100 mL = _______________________

f) 0.15g/ 100 mL = _______________________

Saturated vs. Unsaturated Solution

(Refer to p.264)

Define:

Saturated Solution:

________________________________________________________________________

____________________________

____________________________

Unsaturated Solution:

__________________________________________ ______

____________________________________________________

____________________________

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WEDNESDAY, MARCH 15th

Question:

1. If there are two glasses on Kool Aid on the table, one is unsaturated the other is

saturated. How would you be able to tell the difference between the two?

We are going to assume that both glasses of Kool Aid are the same temperature

and color, and that they both taste the same.

We can tell the difference between the unsaturated and saturated solutions by

adding more Kool Aid powder (solute).

- If the powder dissolves, we know the solution is unsaturated.

- If the powder does not dissolve, we know the solution is saturated.

2. It is possible to “unsaturate a saturated solution”. Suggest ways you might be

able to do this. (Hint: How could you make more sugar to dissolve in a glass of

water?)

We cannot change the amount of solute or solvent.

However, we can increase temperature or pressure.

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Solubility

(Refer to p. 264)

Define:

Solubility:

________________________________________________________________________

____________________________________________

Factors that effect the Rate of dissolving

Factor How does it affect the solubility?

A.

Size of Solute

B.

Temperature

C.

Pressure

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Grade 7 Science Core Lab Activity 8-2A Pages 268-9

Unit 3: Mixtures and Solutions

How Does Temperature Affect Solubility?

Procedure: Part 1 Refer to text page 268.

Complete the graph on the graph paper provided on the next page.

Questions:

1. Describe the shape of the lines on your graph.

2. What happens to the lines as the temperature increases?

3. Predict the solubility of each solute at 90 degrees Celsius?

Sucrose

Potassium Chlorate

Ammonium Chloride

Title: ___________________________________________________________________

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Part 2:

Name: ______________________________

Partners: ____________________________ ____________________________

____________________________ _____________________________

Problem: How does temperature affect the solubility of a solid in a liquid solvent?

Hypothesis:

Materials: graduated cylinder thermometer beaker

sugar cubes stopwatch

Procedure:

Measure 100 mL of cold water for one beaker.

Measure 100 mL of hot water for another beaker.

Record the initial temperatures of both beakers.

Drop one sugar cube in each beaker and record the amount of time it takes to

completely dissolve.

Results:

Sugar Mixture Temperature Temperature

(Class

Average)

Time Time

(Class

Average)

Cold

Hot

Analyze:

How did the solubility in warmer water of the substance you tested compare with its

solubility in colder water?

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

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Key Terms

Dissolves

________________________________________________________________________

________________________________________________________________________

Insoluble

________________________________________________________________________

________________________________________________________________________

Soluble

________________________________________________________________________

________________________________________________________________________

Solute

________________________________________________________________________

________________________________________________________________________

Solvent

________________________________________________________________________

________________________________________________________________________

Concentrated Solution

________________________________________________________________________

________________________________________________________________________

Concentration

________________________________________________________________________

________________________________________________________________________

Dilute Solution

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________________________________________________________________________

________________________________________________________________________

Saturated Solution

________________________________________________________________________

________________________________________________________________________

Solubility

________________________________________________________________________

________________________________________________________________________

Unsaturated Solution

________________________________________________________________________

________________________________________________________________________

Comprehension Questions

1. a) Vinegar in insoluble in vegetable oil. Does this mean that vinegar is a totally

insoluble substance?

________________________________________________________________________

b) Why or why not?

________________________________________________________________________

________________________________________________________________________

2. List two substances that are soluble in water.

i) ________________________________________________________________________

ii) ________________________________________________________________________

3. List two substances that are insoluble in water.

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i) ________________________________________________________________________

ii) ________________________________________________________________________

4. Name a substance that is insoluble in water but is soluble in a different solution.

________________________________________________________________________

5. You put 3 teaspoons of sugar in jug and you put 2 teaspoons of sugar in another jug

exactly the same size. Which jug is more concentrated?

________________________________________________________________________

6. What does the units g/L mean?

________________________________________________________________________

________________________________________________________________________

7. What is the difference between a saturated solution and an unsaturated solution?

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

8. Explain this statement: “The solubility of salt is 357 g/L at 0℃.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

9. How does the size of the solute affect the rate of dissolving?

________________________________________________________________________

________________________________________________________________________

10. Refer to Table 8.2 on page 264.

a) Which is the most soluble substance? ________________________________

b) Which is the least soluble substance? ________________________________

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11. a) Suppose that you add some solid detergent to the water in a washing machine. Then,

you decide that your clothes are really dirty, so you add more detergent. Is the solution

of detergent and water more concentrated or more dilute? Explain.

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

Temperature (0℃) Solubility in Water (g/L)

Sugar Potassium

Chlorate

Ammonium

Chloride

10 1910 50 320

20 2040 70 370

30 2200 110 410

40 2390 150 460

50 2610 210 500

60 2870 270 550

70 3200 340 600

12. Using the table above, which solute has the highest solubility at each of the following

temperatures?

a) 20℃ ______________________

b) 60℃ ______________________

c) 90℃ ______________________

13. Why must you include information about temperature when you state the solubility of a

substance?

________________________________________________________________________

________________________________________________________________________

________________________________________________________________________

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Goal • Use this word search puzzle to review Key Terms from Chapter 8.

Create a list of 11 words from the descriptions below. Then find the words in the puzzle that

follows.

1. A solution in which the amount of solute is high compared to the amount of solvent

2. What happens to a solute such as sugar when it is mixed with water

3. A word used to describe a substance such as glass when it is mixed with water

4. The opposite of the term you found for number 1

5. A solution that has as much solute dissolved in it for a given temperature

6. A word used to describe a substance such as

motor oil when it is mixed with gasoline

7. The amount of solute that will dissolve in a given quantity of solvent at a certain temperature

8. Another name for a homogeneous mixture

9. A word used to describe a mixture such as salt water in which you can still dissolve more salt

10. Term used for what you mix into a substance such as water to form a solution

11. Term used for what you mix with a substance such as salt to form a solution

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Goal • Check your understanding of Chapter 8.

What to Do

Circle the letter of the best answer.

1. Which of the following statements accurately describes a solution of copper in silver?

A. The copper is the solute and the silver is the solvent. B. The copper is the solution and the silver is the solvent. C. The silver is the solute and the copper is the solvent. D. The silver is the solution and the copper is the solvent.

2. Which of the following statements is true? A. Chlorophyll is soluble in water. B. Gasoline is insoluble in motor oil. C. Gasoline is soluble in motor oil. D. Salt is insoluble in water.

3. How is a concentrated solution different from a dilute solution? A. The concentrated solution has a large mass of dissolved solvent for a certain quanity of solute. B. The concentrated solution has a large mass of dissolved solute for a certain quantity of solvent. C. The concentrated solution has a small mass of dissolved solute for a certain quantity of solvent. D. They both have different solubilities.

4. Which statement best describes what is meant by the term “rate of dissolving?” A. how fast a mixture must be stirred B. how fast a solute dissolves in a solvent C. the solubility of a substance at a given temperature D. the temperature at which a solute dissolves in a solvent

5. What happens when you remove the cap from a bottle of pop?

A. The pressure inside the bottle lowers very quickly. B. The pressure inside the bottle remains the same at a certain temperature. C. The pressure inside the bottle rises very quickly. D. The solution increases in pressure at a certain temperature.

6. At 0°C, 357 g of salt will dissolve in 1 L of water. At this temperature, why will no additional salt dissolve? A. The rate of dissolving is equal to its solubility. B. The solution is concentrated. C. The solution is saturated. D. The solution is unsaturated.

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Match the term on the left with the best description on the right. Each description may be used only once.

Term Description

_____ 7. solute _____ 8. solubility _____ 9. solution _____ 10. solvent _____ 11. saturated _____ 12. soluble

A. describes a substance that will dissolve in another substance

B. the mass of a solute that can dissolve in a certain amount of solvent at a certain temperature

C. the mass of a solvent that can dissolve in a certain solute at a certain temperature

D. the substance in which something dissolves

E. a homogeneous mixture

F. the substance that dissolves in another substance

G. describes a solution in which no more solute will dissolve at a certain temperature.

H. describes a solution in which no more solute will dissolve

Short Answer Questions

13. Give examples of each of the following.

solid-in-solid solutions (1) ______________________ (2) ______________________

liquid-in-liquid solutions

(1) ______________________ (2) ______________________

gas-in-gas solutions (1) ______________________

14. Use the particle theory of matter to explain why some substances are soluble in water while other substances are not soluble in water.

_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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15. Suppose that you have a solution of table salt dissolved in water. Explain how you could find out whether or not this solution is saturated.

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

16. The solubility of sugar in water is 1792 g/L at 0°C. How much sugar must be added to 50 mL of water to make a saturated solution at 0°C?

__________________________________________________________________________________________________________________________________

17. The solubility of a substance can be expressed qualitatively and quantitatively. Use examples to explain this statement for sugar dissolved in water.

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

18. In the space to the right, sketch the shape of a graph that shows how the solubility of sugar in water changes as the temperature of the water increases. Label the axes correctly, and title the graph.