Matter
“Food Matters”
Is it a Pure Substance or a Mixture?
• Matter can be divided into two main
categories:
– Pure substances are homogeneous throughout.
They have the same chemical properties no
matter where the sample is obtained or how
large the sample is.
– Mixtures are combinations of two or more
substances, with each substance retaining its
chemical identity.
“Food Matters”
Is it a Pure Substance or a Mixture?
•
•
•
•
•
•
•
Distilled Water – PS
Bottled Water – M
Tap Water – M
OJ – M
Milk – M
Sugar – PS
Salt - PS
Corn Flakes - M
White Vinegar - M
Corn Starch - PS
Plain Choc - M
Crunch Bar - M
Chemistry is the study of …
• ….Matter
• Matter is
anything that
takes up space
and has mass.
• Light and
sound are NOT
matter!!
MATTER IS MADE UP OF…
• …Atoms
• The smallest
particle of an
element
• Indivisible
….that guy is Democritus
– Greek philosopher
– “atomos”
What Does an Atom Look Like?
• Atoms are too small
to see with the eye,
but if we could see
them, they would
look like this….
• But we can see
GROUPS of atoms.
Groups of Atoms are Called…
• …Elements
• …made of IDENTICAL
atoms.
• Examples: Anything on
the Periodic Table
Elements can combine to form…
• …Compounds
• …contain 2 OR MORE DIFFERENT
ELEMENTS (atoms) and are
BONDED (attached) or joined in a
fixed proportion
• Compounds are NOT on the
Periodic Table;
• Compounds are NOT MIXTURES
(we’ll get to those later…)
Identify these as Element(s) or
Compound(s).
A
B
C
D
1 Element
1 Compound
2 Elements
2 Elements
Classifying Matter
• All matter is made out of atoms…
• And all matter can be classified into different
categories!
– Pure Substances
– Mixtures
Mixture
• MIXTURES CAN BE SEPARATED!
• Made up of 2 or more elements or compounds
– Yellow – an ELEMENT
– Red/Blue – a COMPOUND
(Atoms are not really colored. The different colors represent different
elements.)
Pure Substances
(or simply, a substance)
• CANNOT BE SEPARATED
• Can be made up of all one element OR all one
compound
• Examples:
– table salt
– table sugar
• Element
• Compound
Identify these as Pure Substances or
Mixtures.
A
B
C
D
Pure
1 element
Pure
Mixture
Mixture
1 compound
2 elements
2 elements
Pure Substances v. Mixtures
Video
Mixtures
• A combination of more than one
type of substance
• The properties of a mixture can
vary because the make up of a mixture is not
fixed (unlike compounds which have a fixed proportion)
• 2 Types of Mixtures:
– Heterogeneous – the parts of the mixture are
noticeably different from one another
– Homogeneous – the parts of the mixture are so
evenly distributed that it appears to be all the same
substance (but a mixture is more than one
substance!)
Solutions and Suspensions and
Colloids…Oh My!
• A mixture can be further classified into 3
categories based on the size its largest
particles
– Solutions
– Suspensions
– Colloids
Solutions and Suspensions and
Colloids…Oh My!
• Solutions – homogeneous mixtures
– Examples: Sugar dissolved in water, tap water
– Properties of solutions:
• DO NOT separate into layers over time
• If liquid solutions are poured through a filter
none of the substance gets trapped in the filter.
• You can see through liquid solutions
– All of these relate to the size of the particles
- in a solution, they are tiny!
Homogeneous Mixture
• Substances are evenly
distributed
• Appears to contain
only one substance
• Solutions –
homogeneous
mixtures in which one
substance dissolves in
another
Solutions and Suspensions and
Colloids…Oh My!
• Suspensions – heterogeneous mixtures
– Example: sandy water
– Properties of solutions:
• DO separate into layers over time
• If you pour a suspension through a filter some of
the substance in the mixture gets trapped in the
filter.
• Suspensions are cloudy because light gets
scattered in all directions as it hits larger particles.
– All of these relate to the size of the particles in a suspension, they are bigger!
Heterogeneous Mixture
• The parts of the
mixture are
noticeably
different from one
another
• Suspensions
– Separate into
layers
Heterogeneous Mixture
• Suspensions can
be mixed (“Shake
before serving) but
eventually
separate out.
Solutions and Suspensions and
Colloids…Oh My!
• Colloids– somewhere in between
homogeneous and heterogeneous
mixtures
– Examples: milk and fog
– Properties of colloids:
• DO NOT separate into layers over time.
• Cannot use a filter to separate the parts of a colloid
• Light gets scattered when it passes into a colloid
– Contain intermediate sized particles
How Do You Separate A Mixture?
• REMEMBER THE LAB?
• Here are a few other ways to separate
mixtures….
Separation of Mixtures
• Compounds and mixtures differ in another
way.
• It is difficult to separate a compound into each
element.
• Mixtures can be easy to separate into its
components because each component keeps
its own properties.
Separation of Mixtures
1. Magnetic attraction: The magnetic
components of a mixture can be
separated by using a magnet.
Separation of Mixtures
2. Filtration: separates parts of a
heterogeneous mixture by pouring it
though a filter, the larger particles
(residue) will be held in the filter while
the smaller ones (filtrate) will pass
through.
Separation of Mixtures
3.
Distillation: used to
separate components of a
homogeneous mixture
based on their different
boiling points. Solution is
heated and substance with
lower boiling points
evaporates and passes
through a tube where it
cools and turns back into
water in another container.
Separation of Mixtures
4. Evaporation: When a mixture contains
a solvent such as water and a solute
such as salt, the solvent can be allowed
to evaporate, leaving behind the solute.
Separation of Mixtures
5.
Sedimentation: occurs naturally when
solid substances that are heavier than
their solvent deposit at the bottom of
the mixture.
Separation of Mixtures
6. Decantation:
a heterogeneous mixture
that has distinct layers can be separated
by slowly pouring one of the layers into
another container.