Unit A Lesson A5 Solubility Changes
Completion requirements
Lesson A5: Solubility Changes
Video Lesson
How can you make a solute dissolve faster in a solvent? Watch this video to find out how to change the speed of dissolving.
Lesson A5: Solubility Changes
Figure A.2.5.1 – The main ingredient in candy is sugar.
Figure A.2.5.2 – Rock candy is made from a solution of sugar, water, colouring, and flavouring.
Figure A.2.5.3 – Temperature and stirring is important to the process of candy-making.
Reading and Materials for This Lesson
Science in Action 8
Reading: Pages 29–31
Materials:
Wood skewer or popsicle stick, water, sugar, measuring cup, cooking pot, stove, oven mitts, whisk, flavouring (liquid extracts such as vanilla, almond, or mint), food colouring (red, blue, yellow), funnel, tall narrow glass cup or jar, 2 clothespins,
M&M’s™ candies (3 of the same colour), 3 identical clear cups, isopropyl alcohol (rubbing alcohol), baby oil (mineral oil), measuring spoons, timer, baking soda, white vinegar, corn syrup, cornstarch, muffin pan, glass measuring cup (with a
spout), spoon, paper, paintbrush.
Making Candy
Candy is made from a saturated solution of sugar, water, flavouring, and food colouring. The saturated solution must be heated to dissolve all the sugar crystals. When the solution cools again, solid sugar recrystallizes out of the solution, but in a different form.
The texture of candy depends on the concentration of the sugar solution, as well as the temperature to which the solution is heated. Soft candies like fudge have a lower sugar concentration and are heated to a lower temperature. Hard candies like lollipops have a high concentration of sugar and are heated to a higher temperature.
Candy is made from a saturated solution of sugar, water, flavouring, and food colouring. The saturated solution must be heated to dissolve all the sugar crystals. When the solution cools again, solid sugar recrystallizes out of the solution, but in a different form.
The texture of candy depends on the concentration of the sugar solution, as well as the temperature to which the solution is heated. Soft candies like fudge have a lower sugar concentration and are heated to a lower temperature. Hard candies like lollipops have a high concentration of sugar and are heated to a higher temperature.
Watch More
Who Can Make the World Smile?
Making candy involves heating and cooling a sugar solution. While the sugar solution cools, flavouring and colour are added to the candy. This video explains how lemon drop candy is made.
Making candy involves heating and cooling a sugar solution. While the sugar solution cools, flavouring and colour are added to the candy. This video explains how lemon drop candy is made.
Watch this video to learn how candy canes are made.
Try It!
Make Rock Candy
Try this experiment to make your own rock candy!
Materials:
Materials:
- Wood skewer or popsicle stick
- Water
- Sugar
- Measuring cup
- Cooking pot
- Stove
- Oven mitts
- Whisk
- Flavouring (liquid extracts such as vanilla, almond, or mint)
- Food colouring (optional)
- Funnel
- Tall narrow glass cup or jar
- 2 clothespins
Safety Warning
This activity involves hot fluids. It must be completed with the supervision and assistance of an adult.
DO NOT attempt this activity by yourself.
Hot fluids and metal can burn you or others if you are not careful.
Wear oven mitts when handling the hot cooking pot and tall glass.
Never leave a hot stove unattended.
Take care when pouring hot fluids.
DO NOT attempt this activity by yourself.
Hot fluids and metal can burn you or others if you are not careful.
Wear oven mitts when handling the hot cooking pot and tall glass.
Never leave a hot stove unattended.
Take care when pouring hot fluids.
Instructions:
- Dip one end of the wood skewer into water. Then roll the wet wood skewer in some sugar crystals. Set the skewer aside.
- Place 1 cup of water and 3 cups of sugar in the cooking pot.
- Put the pot on the stove. Heat the solution on medium-high heat. Constantly stir the solution slowly with the whisk so it does not burn.
- Keep stirring the solution until it boils and all the sugar is dissolved.
- Stir 5 drops of flavouring and 5 drops of food colouring into the sugar solution.
- Turn off the stove and remove the pot from the burner.
- Place the funnel in the tall glass cup. Ask an adult wearing oven mitts to pour the hot sugar solution from the pot, through the funnel, into the tall glass cup.
- Let the sugar solution cool in the cup for 10 minutes.
- Place the sugar-covered wood skewer into the tall cup. The skewer should not touch the bottom of the cup. Clip a clothespin to either side of the skewer and rest the clothespins on the cup’s rim, to suspend the skewer in the solution.
- Leave the cup and skewer in a safe place for five days. Observe the glass and skewer each day.
- Lift the skewer out of the glass. Your rock candy is ready to eat!
- Watch this video to see this experiment in action.
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
You created a saturated solution because the sugar solute did not completely dissolve in the water solvent at a low temperature.
Heating the sugar solution caused all the sugar in the saturated solution to dissolve. When the solution was cooled, the dissolved sugar could precipitate in large crystals on the stick.
Figure A.2.5.4 – Edible food colouring is water-soluble.
Figure A.2.5.5 – Nail polish is not soluble in water, but it is soluble in nail polish remover.
Solvents
Water-soluble substances dissolve in water. Two examples of useful water-soluble substances are washable ink and fertilizers.
Some substances are not soluble in water. This is an advantage for substances we do not want to wash away. Wood varnishes are not water-soluble because we want them to protect wood from water. Nail polish is not water-soluble because we don’t want it to wash off our fingernails.
However, chemicals that are insoluble in water dissolve in other solvents. Nail polish remover contains a substance called acetone, which dissolves nail polish. Varnish strippers are chemical solvents that dissolve varnish. Industrial cleaners dissolve motor oil and grease that don’t come off easily with soap and water.
Water-soluble substances dissolve in water. Two examples of useful water-soluble substances are washable ink and fertilizers.
Some substances are not soluble in water. This is an advantage for substances we do not want to wash away. Wood varnishes are not water-soluble because we want them to protect wood from water. Nail polish is not water-soluble because we don’t want it to wash off our fingernails.
However, chemicals that are insoluble in water dissolve in other solvents. Nail polish remover contains a substance called acetone, which dissolves nail polish. Varnish strippers are chemical solvents that dissolve varnish. Industrial cleaners dissolve motor oil and grease that don’t come off easily with soap and water.
Try It!
Dissolving Candy Coating
Figure A.2.5.6 – M&Ms were first advertised as the candy that "melts in your mouth, not in your hand."
Try this simple experiment to test the solubility of candy coating in different solvents.
Materials:
Materials:
- Eye protection glasses/goggles
- M&M’s™ candies (3 of the same colour)
- 3 identical clear cups
- Water
- Isopropyl alcohol (rubbing alcohol)
- Baby oil (mineral oil)
- Measuring spoons
- Timer
Safety Warning
This activity involves using isopropyl alcohol. This substance must be used with caution.
Do not directly inhale isopropyl alcohol fumes.
Isopropyl alcohol is very flammable, never use it anywhere near an open flame.
Isopropyl alcohol can cause skin and eye irritation, take care to not come in direct contact with it.
If you do come in contact with it, flush with plenty of water.
Eye protection is recommended with handling isopropyl alcohol.
Do not directly inhale isopropyl alcohol fumes.
Isopropyl alcohol is very flammable, never use it anywhere near an open flame.
Isopropyl alcohol can cause skin and eye irritation, take care to not come in direct contact with it.
If you do come in contact with it, flush with plenty of water.
Eye protection is recommended with handling isopropyl alcohol.
Instructions:
- Measure 1 tablespoon of water into the first cup.
- Note – eye protection is recommended when handling isopropyl alcohol.
Measure 1 tablespoon of isopropyl alcohol into the second cup.
- Measure 1 tablespoon of baby oil into the third cup.
- Add 1 M&Mâ„¢ candy to each cup.
- Observe the cups for 2 minutes.
- Watch this video to see the results of this experiment.
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
The manipulated variable, or the one thing that is changed, is the type of solvent used.
The responding variable, or the results of the experiment, is the solubility of the candy coating.
The controlled variables, or the variables that stay the same in all tests, are the size of the cups, the amount of solvent placed in each cup, the colour of candy placed in each cup, and the amount of time that the candies were exposed to the
solvent.
The candy coating was most soluble in water. The candy coating was least soluble in baby oil.
Figure A.2.5.7 – As its name suggests, watercolour paints require water as a solvent.
Figure A.2.5.8 – Watercolours come in tubes as well as solid pans. Both need water to make the paint flow.
Connections – Art
>> Paint
All paints are made from tiny coloured pigment particles in a binder fluid. Binder fluid makes the pigment stick to a surface.
While watercolour paints are water-soluble, they are not made from a pigment in water. Watercolour paints contain gum arabic, which is hardened sap from acacia trees. Gum arabic makes pigment stick to the paper after the water solvent evaporates. Watercolors still need to be diluted with water, in order for them to flow on paper.
Oil paints are pigments bound in linseed oil. Linseed oil comes from the flax plant. Oil paints straight from the tube are thick and intensely coloured. Oil paints cannot be diluted with water. They require a solvent such as linseed oil. Sometimes additional linseed oil is used as the solvent; sometimes turpentine paint thinner is used as the solvent. These two solvents are also used to clean oil paint brushes.
>> Paint
All paints are made from tiny coloured pigment particles in a binder fluid. Binder fluid makes the pigment stick to a surface.
While watercolour paints are water-soluble, they are not made from a pigment in water. Watercolour paints contain gum arabic, which is hardened sap from acacia trees. Gum arabic makes pigment stick to the paper after the water solvent evaporates. Watercolors still need to be diluted with water, in order for them to flow on paper.
Oil paints are pigments bound in linseed oil. Linseed oil comes from the flax plant. Oil paints straight from the tube are thick and intensely coloured. Oil paints cannot be diluted with water. They require a solvent such as linseed oil. Sometimes additional linseed oil is used as the solvent; sometimes turpentine paint thinner is used as the solvent. These two solvents are also used to clean oil paint brushes.
Figure A.2.5.9 – As its name suggests, oil paints contain an oil binder.
Figure A.2.5.10 – Latex paint doesn’t actually contain natural latex. It is made from a plastic-like substance.
Watch More
How Paint is Made
Watch this video to see how house paint is manufactured.
Watch this video to see how house paint is manufactured.
This video explains how to make paint from ground pigment and egg yolks.
Here’s a fun reminder on how to mix paint colours to create new colours!
Try It!
Make Watercolour Paints
Materials:
- Baking soda
- White vinegar
- Corn syrup
- Cornstarch
- Food colouring (red, blue, yellow)
- Muffin cooking pan
- Glass measuring cup with a spout
- Measuring spoons
- Spoon
- Paper
- Paintbrush
- Water
Instructions:
- Measure 70 ml (4 tablespoons) of baking soda and 35 ml (2 tablespoons) of white vinegar into the glass measuring cup.
- When the mixture stops fizzing, add 3 ml (½ teaspoon) of corn syrup and 2 tablespoons of cornstarch to the mixture. Stir the mixture well.
- Pour the mixture into the cups of the muffin pan. Divide the mixture between 4 to 6 cups.
- Add drops of food colouring to each cup. Mix colours as you wish to get the colours you desire. With a clean spoon, stir to mix the colour with the paint binder.
- Allow the paints in the muffin pan to dry completely over several days.
- Try out your paints! Dip a paintbrush in water, rub it on the watercolor paint, and spread the paint on paper.
- Watch this video to see the results of this experiment.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your
learning.
Unit A Lesson 5 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here .
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
The recipe suggests dissolving baking soda in water so that large chunks of baking soda spread out in water before it is added to the cookie dough. Warm water helps the baking soda dissolve faster. A solution of baking soda is easier to mix
evenly into the cookie dough compared to large chunks of solid baking soda.
Grinding coffee increases the surface area of coffee. This helps coffee flavour particles dissolve into hot water faster.
Adding boiling water to the bouillon cube and stirring helps it dissolve quickly, so it can mix evenly throughout the soup. The bouillon cube has a small surface area, so if it was added to the soup without dissolving and stirring, it would
take a long time to dissolve and might not dissolve completely.
People stir their coffee or tea after adding cream or sugar to make them dissolve faster in the hot drink.
Flavoured extract particles are insoluble in water. However, flavoured extract oils dissolve well in alcohol, which is used as the solvent.