Grade 7 Science

Unit 3:

Mixtures & Solutions:

The Particle Theory

Particle Theory of Matter

All matter is made up of

tiny particles.

These particles are always

moving… they have

energy.

There are spaces among

particles.

There are attractive forces

between the particles.

The particles of one

substance differ from the

particles of other

substances.

Student Activity...

With a partner decide:

1. How would you tell the

difference between a pure

substance and a mixture?

2. How would use the

Particle Theory of Matter

to support your answer to

question #1?

Mixtures vs. Pure

Substances

Mixtures...

MAY have distinct visible

components.

MAY appear uniform

throughout.

They are the physical

combination of two or

more pure substances.

+

Sugar Water

= ?

Examples of Mixtures…

•salt water, kool-aid

•chocolate chip cookie

•muddy water

•salad dressing

•air

Pure Substances... ALWAYS appear as

uniform throughout

They contain either a

single atom or two or more

atoms chemically

combined to form a

different substance.

Examples of Pure Substances

•sugar (C12H22O11)

•gold (Au), copper (Cu)

•distilled water (H2O)

•carbon dioxide (CO2)

•oxygen (O2)

Student Activity...

Read pages 232, 236 and 237

Make a list of 15-20 solutions

and mixtures that you

encounter in a day. * those

that may pose a safety risk.

Grade 7 Science

Homogeneous &

Heterogeneous

Mixtures

Homogeneous Mixture

also called

solutions

can be

solid, liquid

or gas

Stainless steel

the particles

are evenly

mixed so

that none of

the original

substances

are visible Kool-aid

they appear

to be ONE

substance

light passes

through

unaffected

Heterogeneous Mixtures

also called

mechanical

mixtures

can be

solid, liquid

or gas Granola bar

the different

parts are visible

to the eye (may

need a

microscope)

the particles do

not evenly mix

Concrete

Light will

reflect

perpendicula

r to the

direction of

the beam

Student Activity...

Create a chart and list the

various homogeneous and

heterogeneous mixtures in

your home.

Share with your shoulder

partner and add to your

list.

The Tyndall Effect

A phenomenon that can be

used to distinguish between

solutions and what appears

to be a solution

cannot be used to distinguish

between a solution and a

pure liquid

In a Solution...

Light passes

unaffected (if a

student looks at the

beaker perpendicular

to the direction of the

beam they will NOT

see it

In a Mechanical Mixture...

The light will

scatter as it

passes through

the mixture

because all

particles are not

dissolved (as

Both Hetero and

Homogenoeus Mixtures?

Complete Activity 7-1C

Page 238 & 239

Post Activity Discussion...

Enrichment

Colloids

Dispersions

Emulsions