1. Classification of Matter
Chapter 15
Classification of Matter

2. Pure Substances
Materials are made of a pure substance or a mixture of substances
A pure substance, or substance, is a type of matter with a fixed composition
A substance can either be an element or a compound
ex. Helium, Water, Salt

3. Elements All substances are built from atoms
If all atoms in a substance have the same identity, the substance is an element
Ex. Copper, gold, silver
All of the elements are found on the Periodic Table

4. Compounds Two or more elements can combine to form a compound
A compound is a substance in which the atoms of two or more elements are combined in a fixed proportion
Ex. Table Salt
- Compounds have properties different from the elements that compose them
- Definite Ratio
- Can only be decomposed into elements by chemical rxns. (can’t physically separate them)

5. Mixtures
A mixture is a material made up of two or more substances that can be easily separated by physical means
Components retain their own identifying properties
No definite composition
Can be separated by dissolving, filtering, evaporating, magnetics, screening, etc.
Mixtures can either be heterogeneous or homogeneous

6. Heterogeneous mixtures
A heterogeneous mixture is a mixture where different materials can be distinguished easily
Some are easily seen while others are not
Ex. Pizza

7. Homogeneous Mixtures
A homogeneous mixture contains two or more gaseous, liquid, or solid substances blended evenly throughout
Components can’t be seen with the naked eye
Ex. Soft Drink in a bottle – contains water, sugar, flavoring, coloring, CO2 gas

8. Solutions
Solution - A homogeneous mixture in which the components are close to the size of individual particles of the substance and are too tiny to be seen with a microscope and will never settle to the bottom of a container
Solutions remain constantly and uniformly mixed

10. Mixtures can occur between and among all phases of matter
Gas/gas (air)
Gas/liquid (oxygen in water)
Liquid/liquid (alcohol in water)
Liquid/solid – (sugar in water)
Solid/solid – (alloy such as steel)
Ex. The addition of 10-30% chromium creates stainless steel

11. Physical Properties
A physical property of a substance is any characteristic of a material that you can observe without changing the identity of the substances that make up the material
Physical properties can be observed directly of measured with a tool
Examples of physical properties include boiling point, color, shape, size

12. Boiling/Freezing/Melting Points
Boiling/Melting/Freezing points refer not to the phase change itself, but to a measurement: the temperature at which these changes occur
Physical properties because the composition of a substance doesn’t change during phase change or when one measures temperature to determine these points

13. Density Density is the mass of a substance per unit volume
The density of a particular substance (under constant conditions) is always the same, regardless of sample size
The composition of a substance doesn’t change when one measures mass and volume to find density -> physical property
Density = mass
volume

14. Solubility
Solubility – the maximum amount of a solute (substance being dissolved) that can dissolve in a given volume of solvent (the dissolving medium) at a particular temperature and pressure
The components of solutions do not chemically combine to form a new substance, therefore solutions are composed of two substances which each retain their own properties -> physical property

15. Viscosity Viscosity is a measure of a material’s resistance to flow
High viscosity fluids take longer to pour than low-viscosity fluids
The composition of a fluid doesn’t change when it is poured -> physical property

16. Electrical Conductivity
A solid is either an electrical conductor or insulator based on its ability to complete an electric circuit

17. Physical Changes Review
Any observations/measurement made WITHOUT changing the composition of the matter
Color
Texture
Density
Odor
Solubility
Melting/boiling point (Any Phase Change)

18. Physical Change A change in size, shape, state
Identity of the element/compound does not change
Change in Shape/Size
Aluminum Foil cut in half
Chewing your food
Change in State
Rubbing alcohol evaporates in your hand
Juice box freezes in freezer

19. Signs of a Physical Change
Any phase change Change in energy of the particles What you started off with is what you end up with chemically

20. Chemical Properties
A chemical property is a characteristic of a substance that indicates whether it can undergo a change that will alter the composition of the substance
A change of one substance to another
Ex. The capacity to oxidize
The capacity to corrode
Combustibility

21. Chemical Changes
Substance(s) present at the beginning of the reaction are changed into something new.
You BREAK or MAKE bonds!!
The change can’t be undone

22. Examples Gasoline is ignited/burns Car rusts Milk goes sour
Bread -> toast
Food digesting in your stomach and small intestine

23. Signs of Chemical Change
Bubbles appear
Something is burning
A precipitate forms (solid appears)
Color Change
Temperature changes
Smell

24. The Capacity to Oxidize
A substance combines with oxygen to form a new substance with new properties
The new substance formed is a combination of the atoms of the original substance and oxygen
Properties of a substance change during the process of oxidation

25. Combustibility Combustion is a special type of oxidation
When combustion occurs, a substance combines with oxygen to form a new substance with new properties in a process that releases heat and light

26. The Capacity to Corrode
Corrosion – the process by which metals naturally combine with oxygen, sulfur, or other nonmetals
When corrosion occurs, the new substance that is formed is a combination of a metal and a nonmetal
The properties of a substance change during this process

27. Conservation of Mass
The mass of all substances present before a chemical change equals the mass of all the substances that remain after the change (this will be more important later)
Ex. A burning log, even though ashes are left and weigh less, if you could collect all the gases lost during the burning and measure their masses too, mass would be conserved