Transcript Classifying Matter

Classifying Matter
Up to this point, we have only been modeling matter with simple particles
• The simplest units of substances have been represented by just a single particle
water
perfume
aluminum
air
For now, it’s still ok to represent substances this way due to the
fact that we currently have no reason not to think this is how
they actually are (set aside any prior knowledge of what you
think water actually consists of)
• It is time to start considering what occurs when particles of
different substances are mixed
 Majority of things in nature are not 100% pure, they are a mixture of
substances
Why is it even important to classify
matter?
Before we try to realize the importance of classifying matter, maybe we should ask
ourselves why we classify things in the first place? What are some things you
organize in your life by classification?
Though it’s possible to live a life (and even understand chemistry) without
classification, it only makes it more difficult
• We classify things to make life easier and understanding things with greater
ease
• By classifying things in science, it becomes much easier to identify patterns and
make generalizations that eventually change the way we think about a whole
topic
Silver, copper,
aluminum, and gold
conduct electricity
All of these are
metals
Metals conduct electricity
• By following this classification scheme, we are able to make the generalization that
“metals conduct electricity.” Therefore, when people make circuits to provide
electricity, the use metal (usually copper) wiring.
So how is matter classified?
Pure Substances
Mixtures
• Has a definite set of
characteristic properties that
depend only on the nature, not
the quantity of the substance
• Exhibits properties that are a
combination of the properties of
the substances that make it up
 Density, melting point, boiling point,
specific heat, etc.
 For example, water will have a boiling
point of 100 0C regardless if you boil 10
mL or 10 gallons of water
• Composed of more than one kind
of particle
• Composed of only one kind of
particle
 A bar of gold is composed of only gold
particles
 A glass of clean water is composed of only
water particles
 Will not have one set boiling point or melting
point
 A mixture of alcohol and water will contain
alcohol particles & water particles
Knowing the properties of a mixture
allows us to easily separate it
Filtration
 Doesn’t work when one
substance is dissolved in
another
Distillation
 Can be used to separate a mixture of pure substances
based on known boiling points
 Can also be used to purify (distillation of alcohol or
water)
Mixtures and Compounds
mixture of iron and sulfur
Why did the iron maintain its magnetism when simply mixed with sulfur?
 The properties of a mixture are dictated by the properties of the substances that make it up. Iron was
magnetic before the mixture and simply mixing iron and sulfur won’t take away its magnetic properties
Why did the iron not maintain its magnetism after it had reacted with sulfur?
 The reaction of iron and sulfur produced a pure substance known as iron sulfide. Iron sulfide is a
completely different substance than iron so it will not necessarily retain the same properties iron had on
its own
 We know this is a pure substance because it has all new properties and it is composed of only one type of
particle (iron sulfide)
Which are mixtures and which are pure substances?
Mixture:
• B&E
Pure Substance:
• A, C, D, F
A mixture of molecules:
• B
Atoms of a pure metal:
• C
Molecules of an element:
• F
A solid compound
• A
A mixture of elements
• E