Ch 3.3 Solutions and Suspensions

8/12/2019 Ch 3.3 Solutions and Suspensions

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Chapter 3.3 Solutions and Suspensions

Name: ______________________( ) Class: ______ Date: ____________

CHAPTER MAP & OVERVIEW

Learning Outcomes:

Pupils are expected to

(a) distinguish among solute, solventand solution

(b) deduce the nature of solutions and suspensions by simple laboratory tests

(c) investigate the factors that affect the solubility and rate of dissolving of substances

(d) recognise the importance of these factors in homes and industries

(e) interpret solubility graphs and draw suitable conclusions from it

CHAPTER 3.1

SOLUTIONS AND SUSPENSIONS

Formed

when

Homogeneous

Clear

Light can pass through

Solution can pass through

filter paper

Substance does

not dissolve in

solvent

Non-Homogeneous

Cloudy

Light cannot pass through

Residue collected when

passed through filter paper

SuspensionsSolutions

Nature

Solubility

Large amount of

solute present

(>solubility limit)

Large amount of

solute present

(


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Solutions

All solutionsare mixtures that consist of 2 parts:

Solvent: The substance that the solute or solutes dissolve in and it forms the bulk of the

solution

Solute:The substance that dissolves

For example, we can dissolve salt (_solute__) in water (_solvent__) to form a salt solution. Youcan no longer see the salt particles in the water.

Most common types of solutions: solid, liquid or a gas dissolves in a liquid solvent. However,there are also many solutions which are formed by dissolving a solid in another solid, a gas inanother gas or by other combinations of the 3 physical states

For our syllabus, we shall focus mainly on liquid solutions with wateras the solvent, which isknown as an _aqueous__ solution.

There are many other liquid solvents like oil, ethanol, acetone, hexane and so on.

Lets think!Why are solutions considered mixtures?

No chemical changes take place, No fixed composition (i.e. can be in different concentration)

Nature of Solutions

A solution is homogeneous when the colour, density, appearance and other physical and

chemical properties are the same in every part of the solution

The solute particles which are spread evenly in the solvent are too small to reflect or block any light

passing through the solution, the light will pass throughthe solution.

Lets think!

What will happen if a solution is filtered? Will there be any residue left?

No residue as solute particle is too small

Solubility

The solubility of a substance in a solvent is the maximum quantityof that substance which candissolve in 100 g of the solventat a given temperature(Units: g/100g)

E.g. Copper(II) sulfate has a solubility of 32 g / 100 g of water at 20 C.

This means that a maximum of ____32______g of copper(II) sulfate can dissolve in 100 g of water

at 20 C.

Describing solutions

A dilutesolution contains a small amount of solute in a large volume of solvent.

A concentratedsolution contains a large amount of solute dissolved in its solvent.


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A saturatedsolution is one which contains a large amount of solute dissolved in its solvent

such that no further solute can dissolve.

Copper(II) sulfate / g 2 30 32 40

Water / g 100 100 100 100

Description dilute concentrated saturated

Suspension (not

covered yet)

Table of Solubilities

Substance Solvent Temperature / C Solubility / (g / 100 g)

Copper(II) sulfate Water 20 32

Copper(II) sulfate Water 80 84

Iodine Water 20


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ActivityThink about dissolving sugar in water to make sugar syrup.What do you think are the factors affecting the rate of dissolvingof the sugar?

1. Temperature

2. Rate of stirring3. Surface area of solute

Suspensions

When we add sand to water, the sand does not dissolve in the water, and we obtain a suspensionof sand in water. We can see the sand particles in the water.

Solution Suspension

A suspension is formed when the substance does not dissolve in the solvent or when the

amount of substance present is over its solubility limit

Nature of Suspensions

A suspension is usually non-homogeneous.

The insoluble particles in a suspension are big enough to prevent light from passing throughthesuspension.

When a suspension is left to stand for some time, the particles will settle to the bottom.

ActivityCompare between the properties of a solution and a suspension.

Solution Suspension

What happens when it is passed

through filter paper?

Solution passes through Insoluble particles collected

as residue

What happens when it is left tosettle?

No visible change Particles settle at bottom

Is it homogenous (same

throughout)?

Yes No

Can light pass through? Yes No

Documents

Ch 3.3 Solutions and Suspensions