1. Chapter 2: Properties of Matter
Chemistry

2. 2.1 Classifying matter:
Composition: the combining of parts into a whole
Pure substances: always have exactly the same composition
Examples: table salt, sugar
Uniform composition= samples have the same properties
Can be classified into: elements and compounds

3. Elements Substance that can’t be broken into simpler substances
~100 exist
Atom: smallest particle of an element
Fixed composition: contains one type of atom
Each element has a specific type of atom

4. Elements Examples: Symbols: Solids- aluminum, carbon
Gases- oxygen, nitrogen
Liquids- only 2 are liquid at room temperature [mercury and bromine]
Symbols:
1813, Berzelius (Swedish chemist)
One or two letters
1st capitalized and 2nd lower case
Based on Latin names of elements
i.e.: gold = Au or aurum
Easy communication

5. Compounds Contains 2 or more elements joined in a fixed proportion
2 hydrogen to 1 oxygen = water
Properties are different from the individual substances that they are made of
ie: oxygen and hydrogen versus water

6. Mixtures
2 or more substances that are not chemically combined and can be separated
Properties can vary: composition is NOT fixed
Can retain properties of the substances being combined
Classified by how well distributed the substances are in the mixture

7. Heterogeneous & Homogeneous Mixtures
Heterogeneous: parts of a mixture are noticeably different from one another
ie: sand, salad
“hetero” = different; “genus” = kind
Homogeneous: substances are distributed evenly & it’s hard to tell one from another
Appears to be made of one substance
ie: water in a swimming pool, stainless steel

8. Solutions, Suspensions, and Colloids
Def: based on size of the largest particles
Solution: when substances dissolve and form a homogeneous mixture
ie: tap water, windshield wiper fluid
1. Do not separate into layers over time
2. Cannot filter to separate
3. Allows light to pass through

9. Suspensions
Def: a heterogeneous mixture that separates into layers over time
“Shake well before using”
ie: sand in water
1. Can be filtered to separate
2. Appear “cloudy”
3. Scatter light in all directions

10. Colloids 1. Do not separate into layers
2. Cannot use a filter to separate
3. Scatters light
ie: fog, homogenized milk

11. 2.2 Physical Properties
Def: any characteristic observed or measured without changing the composition of the substance(s)
Examples: viscosity, conductivity, malleability, hardness, melting point, boiling point, and density

12. Viscosity Def: a liquid’s resistance to flowing
Greater viscosity = slower the liquid flows
Lower viscosity = faster the liquid flows
Honey is more viscous than water
Usually decreases when heated (thins out)
ie: Motor oil has to have the correct viscosity in different temperatures

13. Conductivity Def: a material’s ability to allow heat to flow
Conductors: have high conductivity
Metals
Usually a good conductor of electricity
Insulators: have low conductivity
Woods
Usually a bad conductor of electricity

14. Malleability Def: ability of a solid to be hammered without shattering
Most metals (gold) are very malleable
Ice and glass are not very malleable
Brittle: solids that shatter when struck

15. Hardness Def: how hard a solid is
Compare by scratching one material on another
Kitchen knife against copper sheet
Diamond is the hardest known material

16. Melting, Boiling, and Density
Melting and boiling points:
Melting point- temp at which substance changes from solid to liquid
Boiling point- the temp at which substance changes from liquid to vapor
Specific to each compound or element
Density: ratio of mass to volume (g/cm3)
Used to test purity of a substance

17. Separating Mixtures
Filtration: separates materials based on size of particles
ie: coffee filters, wire screen
Distillation: separates substances in a solution by boiling point
i.e.: fresh water for submarines

18. 2.3 Chemical Properties
Def: ability to produce a change in the composition of matter
observed when substances change into different substances
Examples: flammability and reactivity

19. Flammability and Reactivity
Flammability: material’s ability to burn in the presence of oxygen
ie: gasolines, fabrics, drywall
Reactivity: how readily a substance combines chemically with other substances
oxygen with iron and water = rust
nitrogen gas can be used to slow rust production

20. Chemical & Physical Changes
Physical Change: properties change, but substances stay the same
ie: phase changes, slicing foods, crumpling paper
Most can be reversed, but not all
Chemical change: substance reacts and forms one or more new substances
ie: baking/cooking, food digesting
1. Unexpected change in color
2. Production of a gas
3. Formation of a precipitate

21. Chemical versus Physical Change
Are different substances present after?
Yes- chemical change
No- physical change
Examples?

22. Chapter 3: States of Matter

23. 3.1 Solids, Liquids, and Gases
States of Matter: classified based on whether shapes and volumes are definite or variable
Solids: definite shape & definite volume
ie: pencil, desk, chalkboard
Orderly arrangement of particles at atomic level
Liquids: take shape of container & definite volume
ie: water at room temp, pop, juice
Slightly random arrangement of particles at atomic level

24. Gases and Other States Gases: no definite shape and no definite volume
ie: helium, “air,” natural gas
Takes the shape and volume of its container
Random arrangement of particles at the atomic level
volume: can be compressed or expanded
Plasma:
99% of all observable matter
Extremely high temperatures
Bose-Einstein
BEC: predicted by Einstein in the 1920s, accepted in1995
-273oC, extremely low temperatures
Groups of atoms behave as a single particle

25. Kinetic Theory: Gases
Def: all particles of matter are in constant motion
Kinetic energy: energy an object has due to motion
Gases: constant motion allows gases to fill containers of any size/shape
Constant, random motion
Motion of particles unaffected by other particles (unless in collision)
Forces of attraction among particles can be ignored most of the time

26. Kinetic Theory: Liquids & Solids
Liquids: particles have motion slower than gases & faster than solids
Particles flow to new locations & take shape of container
Volume constant because forces of attraction keep particles close together
ie: students moving through crowded hallways, airports
Solids: particles have “slowest” motion, vibration
Definite shape and volume
Particles vibrate around fixed locations
ie: people in a movie theater, in a car on a road trip

27. 3.3 Phase Changes
Phase change: reversible, occurs when a substance changes from one state to another
Common phase changes: melting, freezing, vaporization, condensation, sublimation, and deposition
Temperature: the temp of a substance does not change during a phase change
Phase change graphs
Melting point = freezing point
Boiling point = condensation point

28. Energy and Phase Changes
Energy is absorbed or released during a phase change
Endothermic: system absorbs energy
ie: ice melting
Exothermic: system releases energy
i.e.: water freezing into ice

29. Melting and Freezing Melting: endothermic; going from solid to liquid
Molecules gain energy to overcome attractions between particles
Complete: all particles have enough energy to “flow”
Freezing: exothermic; going from liquid to solid
Molecules release energy and attractions between particles have effect
Complete: particles vibrate in place
Solids at room temperature freeze at very high temps

30. Vaporization Def: substance changes from liquid to gas, endothermic
Evaporation: liquid gas at temps below the boiling point
Takes place at the surface of a liquid
Vapor- gas phase of a substance that is usually solid or liquid at room temp
Vapor pressure- caused by collisions of vapor and walls of a container
Boiling: vapor pressure becomes = to atmospheric pressure
Molecules below surface have kinetic energy to overcome particle attractions
Bubbles quickly rise to the surface & burst

31. Condensation Def: substance changes from gas or vapor to liquid
Exothermic
i.e.: Fog on mirror, dew on grass

32. Sublimation and Deposition
Sublimation: substance changes from solid to gas or vapor without changing to a liquid 1st
Endothermic
ie: dry ice
Deposition: gas or vapor changes directly into solid without 1st changing to a liquid
Exothermic
ie: frost on windows