January – March 2009
- What is chemistry?
- Who studies chemistry?
- What is a mixture?
- What is a solution?
- What do you hope to learn
in this unit?
Task:
Find the differences between these pairs:
Glass & Steel
 Water & Milk
 Gasoline & Oil


Resemblances:
›
›
›
›

Solid
Construction materials
Can be melted
Cannot bend in original state
(without being melted)
Differences:
›
›
›
›
Color (glass is transparent, steel is grey)
Weight (steel is heavier, if the size is the same)
Steel (metal) can conduct electricity
Glass is fragile, steel is not easily broken

Resemblances:
› Liquid
 They can freeze and evaporate
› We can drink them
› Good for our health
› Nonflammable (cannot catch fire)

Differences:
›
›
›
›
›
Color (water is clear, milk has color)
Water is transparent, milk is not
Water is more widespread on earth (2/3)
Water is naturally on Earth, milk comes from cows
Milk is thicker than water

Resemblances:
›
›
›
›

Liquid
Transparent
Combustible (can catch on fire)
Mixture (not pure substances)
Differences:
›
›
›
›
›
Color (oil has color, gasoline is clear)
Smell
Oil is thicker than gasoline
Gasoline is what we put in our cars
Cooking oil can be used in a kitchen
Module 2 :
Pure Substances and Mixtures
4.1 - Matter in Your World

Matter: any material that occupies space and
has a mass (includes all solids, liquids, and
gases).

Properties: the characteristics that are used to
describe matter.
 Examples: size, shape, form, state, smell, color, taste,

*Every material has its own set of properties.
Example

Water at the beach (photo on page 98) has
the following properties:
Clear, liquid
colorless
odorless
Freezes at 0º C *
(under normal
conditions)
 Boils at 100º C





Some materials cannot be described by
a single set of properties.

Mixture: a material that has more than
one set of properties. It contains more
than one kind of matter combined in such
a way that it keeps its own set of
properties.
 Two
or more substances combined
together is a mixture.
 Heterogeneous:
means made up of
parts, or mixed. A heterogeneous
mixture is made up of parts that
can be seen and observed.
 Homogeneous
mixture : means
every part of the material is the
same. There is only one set of
properties.

Examples: water, air
Heterogeneous or Homogeneous?
What do you think?
1.
2.
3.
4.
5.
6.
7.
Water with salt in it
Apple juice
Peanut butter
Salt and pepper mixed together
Smoothie
Orange juice with pulp
Pure water
A Classified Photograph- Activity (p. 101)
Study the photograph on p. 98.
1.
Make a table (like the one on p. 101)
2.
Find 10 substances in the image.
3.
Classify whether each material is
heterogeneous or homogeneous. Record your
decision in the second column of your table.
4.
In the third column, identify what made you
decide (observations).
Quiz 4.1

The quiz on section 4.1 :
 5 definitions (matter, properties,
homogeneous, heterogeneous,
mixture)
 Examples
Study time!!

Study your 5 definitions (matter,
properties, mixture, homogeneous,
heterogeneous)
 Write them down!
 Study with a partner (no laptops)

Make a list of as many properties as you
can think of.
4.2 – What is a mixture?

Anything with at least two distinct sets
of properties (characteristics) is a
mixture of at least 2 materials.

Examples: sand, pop, sandwich
(All are heterogeneous.)

When a mixture’s different parts can be
identified this easily, the mixture is
usually called a mechanical mixture.

Even so-called “homogenized” milk
turned out to be a heterogeneous
mixture.

It looks homogeneous. With your eyes
only, you cannot detect bubbles or bits
with a different set of properties.

With a microscope, the milk contains
many tiny elements of a second liquid –
fat. No matter how smooth milk appears,
it is actually a heterogeneous mixture.
By now you may be wondering …

Is anything homogeneous?

Is everything heterogeneous?

Isn’t anything pure?

Is everything on Earth really a mixture?

Can a mixture be homogeneous?
Homogeneous Mixtures

A homogeneous mixture is called a
solution.

Solutions are everywhere. 2/3 of Earth is
covered with a liquid solution - the water
of the oceans.

Earth is surrounded by a gas solution that
we call air – a homogeneous mixture of
oxygen, nitrogen, and other gases.
Homogeneous Mixtures

There are even solid solutions, such
as a sterling silver.
 (Sterling silver is a solution of silver and
copper.)
What to do now…
1.
Sciencepower p. 107. Do the activity
2.
Answer questions 1 of “What to do”.
When you are done, complete # 2, 3,
4.
3.
In Sciencepower p. 111 complete # 1
and # 2 a). We will correct in a few
minutes.
in the yellow square “Homogeneous
Mixtures”.
Answers
#1. How may sets of properties do you
need to observe in order to classify a
material as a heterogeneous mixture?
-Anything with two or more distinct
sets of properties.
2. a) What is a solution?
-A homogeneous mixture is a solution.
4.3 – Mixtures and Pure Substances

We have seen that heterogeneous
mixtures have two sets of properties.

There are also homogeneous mixtures,
which have properties that are a blend.

The blend of properties depends on how
much of one material and how much of
the other material are in the mixture.

Are there any pure substances –
materials whose properties are not a
blend and are always the same?
√ Yes there are pure substances.
 Examples: gold, oxygen, copper,
aluminum, silver, sugar, salt, etc.
How can you find a pure substance?
1.
First you look to see if the material is
homogeneous. A pure substance must
be homogeneous.
2.
Investigate (observe) the properties
of the material to find out if they are
always the same.
3.
If they re all exactly the same in all
parts of the material, no matter what
part of the world the material comes
from, then you may conclude that
you have a pure substance.
4.
A thorough investigation is
necessary before anything can be
classified as a pure substance.
What we have seen so far about matter
All materials
Heterogeneous
materials
Homogeneous
materials
Homogeneous
mixtures
Pure substances
A Theory

How can pure substances always be the
same?

How can solutions have blended
properties but still be homogeneous?

To answer these questions, scientists
need a theory (explanation).

The theory that scientists use to explain
the properties of various mixtures and
substances is called the particle theory
of matter.
1.
All matter is made up of extremely tiny
particles.
2.
Each pure substance has its own kind
of particle, different from the particles
of other pure substance.

Based on the particle theory, a pure
substance is a material made up of only
one kind of extremely small particle.

According to the particle theory, all
water particles are exactly the same.

Pure water, no matter how or where it is
obtained, always contains identical
particles.

Similarly, all particles of table
sugar are exactly the same.

They are different from water
particles, different from the particles
of any other substance.

But all the particles of table sugar
are the same.
Lets see how well you understood…
1.
Turn to p. 115 in Sciencepower.
2.
Answer to questions #1. a, b, c and
#2. a, b, c, d.
3.
In Sciencepower p. 118 # 6
4.
We will correct the exercise
together in 10-15 minutes.
Answers « Pouring? Shaping? Filling? (p. 115)
1. Name the state(s) in which a material:
a) has a fixed shape?
A - solid
b) takes the shape of its container
B - liquid
c) always fills watever container it is in
C - gas
2. Name the state(s) in which the particles
are:
a) far apart from each other
C – gas
b) relatively close together
B - liquid
c) free to move around
C - gas & B - liquid
d) held in fixed positions
A- solid
Date
1.
Introduction – Chapter 5
2.
Section 5.1 definition - dissolution
3.
Comic strip