1. Classifying Matter
Why are elements and compounds classified as pure substances?
How do mixtures differ from pure substances?
What is the main difference among solutions, suspensions, and colloids?

2. Pure Substances
every sample of a given substance has the same properties
substance has a fixed, uniform composition
Types of Pure Substances
elements
compounds
molecules

3. Elements
a substance that cannot be broken down into simpler substances
example: If I keep cutting a copper wire into smaller and smaller pieces, the tiniest piece is still copper

4. Elements
An element has a fixed composition because it contains only ONE type of atom
atom
smallest particle of an element
NO two elements contain the same type of atom
There are only about 100 elements
located on the periodic table

5. Compounds a substance that is made from two or more simpler substances
elements
other compounds

6. Compounds Compound Properties
DIFFER from those of the substances of which its made
example: water
made of hydrogen and oxygen (gases)
water is a liquid
hydrogen and oxygen fuel fires
water puts out fires

7. Compounds always contains two or more elements in FIXED proportion
Example: Water
scientific name: dihydrogen oxide
scientific formula: H2O
must have 2 hydrogen atoms and 1 oxygen atom
differs from hydrogen peroxide (H2O2), which must have 2 hydrogen atoms AND 2 oxygen atoms

8. Molecules vs. Compounds
formed when two or more atoms join together chemically
NOT all molecules are compounds
example: H2, O2, N2
Compounds
a molecule that contains at least two different elements
all compounds are molecules
example: H2O, CH4, CO2

9. Hunting the Elements PBS Nova video Periodic Table
elements listed with symbols
first letter = capitalized
second/third letters = lower case
allows scientists from all over the world to communicate effectively

10. Mixtures The blending of two or more dissimilar substances
NOT chemically combined
Classified by how well parts are distributed:
homogeneous- evenly distributed
heterogeneous-NOT evenly distrubuted
Types of Mixtures
suspension
colloid
solution

11. Mixtures-properties
tend to retain some of the properties of their individual substances.
But the properties of a mixture are less constant than the properties of a substance.
The properties of a mixture can vary because the composition of a mixture is not fixed.
Example: Salsa

12. Mixtures-classification
heterogenous mixture
parts of the mixture are noticeably different from one another
Examples: salsa, sand, Lucky Charms
homogeneous mixture
Substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another
Appears to contain only one substance
Example: a spoon (iron, chromium, nickel), salt water, sugar water, lemonade

13. NOT easy to distinguish between mixture types!
You may need to observe the properties of a mixture before you decide.
Particle size affects mixture properties
Classifying Mixtures
based on the size of its largest particles
solution
suspension
colloid

14. Solutions A dissolved substance forming a homogeneous mixture
EX: Saline Solution
Windshield Wiper Fluid
Particles in a Solution are TOO SMALL:
to settle out
to be trapped by a filter
to scatter light

15. Suspensions
A heterogenous mixture that separates into layers over time
EX: Italian Dressing
Muddy Water
Over time the suspended
particles SETTLE to the bottom
CAN separate particles with filters
Larger particles SCATTER light
cloudy

16. Colloids
Contains some particles that are intermediate in size between small particles in a solution and the larger particles in a suspension
EX: Homogenized Milk (fat + liquid)
Jello
Do NOT separate into layers
CANNOT separate with filter
DO scatter light