Transcript Lesson 3: Pure Substances and Mixtures

How Do We Make New
STUFF
From Old
Stuff?
Chalk
Calcium Carbonate CaCO3
Comparing Chalk
Characteristics
Same
Different
Size
Hardness
Malleability
Weight
Mass
Color
Texture
Shape
Use the chart to compare A, B and C.
Matter can be divided into to broad categories:
Pure Substances and Mixtures
Pure Substance
A pure substance is composed of one type of atom or
molecule.
– Elements are substances that are made up of a single type
of atom.
– Molecules are substances that are formed when two or
more atoms join together chemically.
– Compounds are molecules that contain at least two
different elements.
NOTE:
All compounds are molecules
but not all molecules are compounds.
Elements
Elements are pure substances because they are each
made up of one type of atom.
An element is uniform all the way through.
Over 100 elements are organized
on the periodic table of elements.
Elements cannot be broken into simpler parts
EXCEPT during nuclear reactions.
Molecules
Molecules are substances that are formed when
two or
more like or unlike atoms join together chemically.
Compounds
Compounds are molecules
that contain at least two different elements
which are combined chemically in some way.
Compounds cannot be separated by physical means.
Separating a compound requires a chemical
reaction.
Which one represents a PURE SUBSTANCE?
Mixture
A mixture is composed of different types of atoms or
molecules that are not chemically combined. The
substances in a mixture do not chemically react with
one another. Mixtures can be separated by both
physical and chemical means.
There are two types of mixtures:
Homogeneous mixtures
Heterogeneous mixtures
Homogeneous Mixtures
A homogeneous mixture is a type of mixture in
which the composition is uniform and every part
of the solution has the same properties.
Homogeneous mixtures are also called
solutions.
CuCl2 + H20
Heterogeneous Mixtures
A heterogeneous mixture is a mixture of two or more
chemical substances that remain physically separate.
Different regions of a heterogeneous mixture have
different properties.
Chalk
Calcium Carbonate CaCO3
Comparing Chalk
Characteristics
Same
Different
x
Size
Hardness
x
Malleability
x
Weight
x
Mass
x
Color
x
Texture
x
Shape
x
Properties
• Properties are characteristics of substances that
scientists use to describe substances, to help
identify substances, and to distinguish substances
from each other.
• The properties of a substance stay the same
regardless of the substance’s shape or size.
– Examples of properties include color, hardness,
density, and melting point.
– Non-examples of properties include mass, volume,
weight, shape
Molecule
Choose a food item.
State whether the item is a
pure substance or a mixture.
Support your claim with
evidence and reasoning.