Transcript Grade 7 Science

Grade 7 Science
Unit 3:
Mixtures & Solutions:
The Particle Theory
What kind of coin is this?
How big is it?
What color is it?
What is its shape?
What is the texture like?
What is it made of??
We will learn:
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Identify different mixtures in your home
and world around you
Distinguish between heterogeneous and
homogenous mixtures
Distinguish between mixtures and pure
substances using the PTM
Getting Started (page 228)
http://www.youtube.com/watch?v=hIYdxQuzb60&safety_m
ode=true&persist_safety_mode=1&safe=active
Mixed or Pure?

Suppose you pick up a rock on the
beach. You see there are some parts of
it that are grey, white, blue. You
conclude that the different-coloured
parts of the rock must be different types
of matter. Is this a reasonable
conclusion?
Mixed or Pure?
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With a partner, select two of the
following pairs of items and list as many
differences as you can:
Vinegar and water
Aluminum foil and plastic wrap
Steel and glass
Molasses and cooking oil
Metal paper clips and saw dust
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.
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
Examples of Mixtures…
•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.
Limestone- A Pure Substance
(Calcium Carbonate)


Limestone is a sedimentary rock
composed of calcium carbonate
(CaCO3).
Has many uses: including as building
material, filler in products such as
toothpaste or paints.
Water- A Pure Substance

Water is a chemical substance with the
chemical formula H2O. A water
molecule contains one oxygen and two
hydrogen atoms connected by covalent
bonds.
Examples of Pure
Substances
•sugar (C12H22O11)
•gold (Au), copper (Cu)
•carbon dioxide (CO2)
•oxygen (O2)
A Quick Review of chapter so far:
USING THE PARTICLE THEORY OF MATTER WE
CAN DISTINGUISH BETWEEN A PURE
SUBSTANCE AND A MIXTURE
Pure Substance: has only ONE type of particle
Example: gold, iron
Mixture: has 2 or more types of substance in it. We can also
say it has 2 or more types of particles mixed together
Example: sweetened water
Pure Substances:
Pure Substances:
•Pure Substances ALWAYS appear as uniform (the
same) throughout
Mixtures:
Mixtures are the combination of two or more types of
substances.
Sugar –
pure substance
Waterpure substance
Mixture
The Particle Theory Can help
explain the difference between
pure substances and mixtures:
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.
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
Granola bar
called
mechanical
mixtures
 can be
solid, liquid
or gas
 the
Concrete
different
parts are visible
to the eye (may
need a
microscope)
 the particles do
not evenly mix
 Light
will
reflect
perpendicular
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 shown
on the left)
Both Hetero and
Homogenoeus Mixtures?
Complete Activity 7-1C
Page 238 & 239
Post Activity Discussion...
Enrichment
Colloids