SOLUBILITY AND DISSOLVING - WordPress.com · 2015. 11. 28. · PLENARY Filtering will separate a...

SOLUBILITY AND DISSOLVING

© cgrahamphysics.com

MULTIPLE-CHOICE QUIZ


BY THE END OF THE LESSON YOU SHOULD BE ABLE TO…

•  Use the correct terms when talking about dissolving

•  Understand what is happening to the particles when something dissolves.

•  Explain how temperature affects solubility


WHAT IS A SOLUTION?

A solution is a special type of mixture that is made when one substance dissolves and mixes fully with another.

For example, a cup of instant coffee is a solution.

The solid that dissolves (e.g. coffee granules) is called the solute. The liquid that does the dissolving (e.g. hot water) is called the solvent.

How many other solutions can you think of? © cgrahamphysics.com

SOLVENTS AND SOLUTES

tea

flavours and sugar

salt

flavours/sugar/carbon dioxide

flavours and alcohol

water

water

water

water

water

black tea

orange squash

seawater

wine

fizzy drinks

substance solvent solute

What is the solvent and what is the solute?


SPECIAL SOLUTIONS

Solutions do not have to be made from a solid and a liquid. Solutions can also be made by dissolving a gas into a solvent.

Liquids can also be dissolved in other liquids, like alcohol in wine, and solids can even dissolve in other solids.

For example, it is the dissolved oxygen in water that allows fish to breathe.


TEST YOUR LEARNING

•  If a solid dissolves in a liquid then the solid is called the

•  _ _ _ _ _ _

•  SOLUTE •  If a solid dissolves in a

liquid then the liquid is called the

•  _ _ _ _ _ _ _

•  SOLVENT


DO YOU REMEMBER?

•  If a solid dissolves in a liquid then the mixture is called a •  _ _ _ _ _ _ _ _

•  SOLUTION


CAN YOU COMPLETE THE LABELS? Discuss

solvent

solute

solution

Saturated solution © cgrahamphysics.com

DOES A SOLID KEEP DISSOLVING?


DOES TEMPERATURE EFFECT SOLUBILITY?

Method •  A Use a spatula to add 1 spoon of sugar to 10cm3

of ice water in a boiling tube. •  B Stir gently all the time, until all the sugar has

dissolved. •  C Keep adding sugar, one spoon at the time, until

no more sugar dissolves. •  D Write down how many spoons of sugar could be

dissolved in cold water •  E Repeat the experiment for water at room

temperature (20 degree) and boiling water •  F How much sugar will dissolve in oil?


WHY IS SUGAR SOLUBLE IN WATER BUT NOT IN OIL?

•  Oil is not strongly attracted to sugar •  Despite the oil surrounding the

sugar molecules, they do not have sufficient attractive forces to pull an individual sugar particle from the larger sugar cube •  The cube doesn’t dissolve


HOW DOES TEMPERATURE AFFECT SOLUBILITY?

Does sugar dissolve in cold tea?

It does, but not as much as in a cup of hot tea. The sugar is more soluble at higher temperatures.

The amount of a solute that can dissolve at a given temperature is called its solubility.

How does temperature affect the solubility of a substance?

The solubility of a substance usually increases as the temperature increases. © cgrahamphysics.com

SATURATED

Model saturation: •  We are going to Imagine that you are a sugar

cube and you are trying to be dissolved by a solution.

•  For each sugar particle you will need 2 water molecules to keep the sugar dissolved.

sugar water

Saturated solutions animation.swf © cgrahamphysics.com

A SATURATED SOLUTION…


PLENARY

Filtering will separate a dissolved solid from a liquid. False

If you add more solid to a saturated solution it will dissolve. False

If you pour some water into a wide, shallow dish, more solid will dissolve. False

If you stir a saturated solution, more of the solid will dissolve. False

If you add more liquid to a saturated solution, more of the solid will dissolve True

If you heat a saturated solution, less of the solid will dissolve. False


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