Chapter 6 Classification of Matter
Pure substances can be classified into two types…
elements
• cannot be broken down into other pure substances
• are made up of only one type of atom
• only 115 known elements today
• properties of each element is different from those of every other
element
• atoms are like letters in the alphabet; they are the building
blocks upon which all matter is built.
compounds
• can be broken down into elements: they are combinations of
elements
• these are not mixtures – they have NEW properties totally
different from the elements from which they are made.
• when two atoms combine together, they form molecules
• compounds (molecules) are like words made up of elements
(atoms)
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Consider the following:
sodium and chlorine (see Periodic Table of the Elements)
2 sodium
atoms
1 chlorine
molecule
2 sodium chloride
molecules
• sodium is a dangerous, highly reactive metal that burns when it
touches water.
• chlorine is a green, highly poisonous gas.
• when they react and combine – they form a white crystal that
you put on your french fries!
How many differences can you see between the start materials and
the finish materials?
A chemical formula is a short-hand sentence that uses symbols and
numbers to describe what kind of elements and how many of each
element is present in each molecule of a compound.
Check out the table
2
Common name
of compound
Elements combined into compound
Chemical
formula
water
hydrogen oxygen
H2O
table salt
sodium
chlorine
NaCl
carbon dioxide
carbon
oxygen
CO2
glucose
carbon
hydrogen oxygen
C6H12O6
chalk
calcium
carbon
CaCO3
baking soda
sodium
hydrogen carbon
copper
sulphate
copper
sulfur
oxygen
oxygen NaHCO3
oxygen
CuSO4
How many of each atom are in___________________________________________ ?
Review 6.1 In class
Changes in Matter
…in chemistry there are two basic flavours:
chemical
• new substances with new properties are produced
• molecules are rearranged into new ones
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• appearance change
• change is not easily reversed
physical
• no new substances or properties are observed
• appearance change
• change is easily reversed
How can you tell the difference between the two?
In chemical usually one or more of the following occurs:
1. a new colour appears
2. heat or light is given off
3. bubbles of gas are produced
4. difficult to reverse (again, i know!)
Review 6.2
Properties of matter
Quanititative – when you use numbers to describe quantity. (weight,
volume, time, melting point, density etc.)
Qualitative – when you use your 5 senses to describe quality. (colour,
slipperiness, smell etc.)
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melting point – the point at which a pure substance changes from
solid state to liquid state. (e.g. water = ___________ ?)
freezing point - the point at which a pure substance changes from
liquid state to solid state. (e.g. water = ___________ ?)
boiling point - the point at which a pure substance changes from
liquid state to vapour state. (e.g. water = ___________ ?)
What state am I in?
substance
melting
point (oC)
boiling
point
(oC)
alcohol
-115
78
copper
1084
2336
oxygen
-218
-183
salt
801
1465
sulfur
113
445
water
0
100
state at 20oC
density – how much a unit (one!) volume of a material
weighs…usually measured in
__grams__
cm3
marshmallow
wood
water
iron
5
Which one of these four items of equal volume (1 cm3) weighs the
most? The least? Which one of these four items of equal volume (1
cm3) has the greatest density? The least?
How could you qualitatively test them?
How could you quantitatively test them?
Calculating density
• Find the mass of the object (scale)
• Find the volume
o By multiplying depth X height X width
o By displacement of water in a graduated cylinder
• Calculate density by
density(d) = ___mass(m)___
volume (v)
Method 1
h
w
d
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Method 2
Review 6.3
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6.4 Mixtures
All matter can be classified into one of the following categories in this
chart:
Matter
Mixtures
Pure substances
Mechanical
Suspensions
Solutions
Element
Compounds
clumping of
partial clumping
particles of different
one type of
two ore more
substances
of one of the
substances are
atom
types of atoms
substances
completely mixed
combined
together
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