1. Chapter 2: Properties of Matter
Section 2.1 Classifying Matter
Section 2.2 Physical Properties
Section 2.3 Chemical Properties

2. Section 2.1: Classifying Matter
Pure Substances
What is Matter? Anything that has mass and takes up space (volume)
Based on matter’s composition, it can be divided into Pure Substances and Mixtures.

3. Section 2.1: Classifying Matter
Pure Substances
Def.-matter that always has exactly the same composition (ex. Table salt, table sugar)
Key Concept: Every sample of a given substance has the same properties because a substance has a fixed, uniform composition.
2 Categories of substances: elements and compounds

4. Section 2.1: Classifying Matter
Elements
Def.-a substance that cannot be broken down into simpler substances
Key Concept: An element has a fixed composition because it contains only one type of atom.

5. Section 2.1: Classifying Matter
Elements: Examples of Elements
Carbon (C), Aluminum (Al)- solid at RT
Oxygen (O), Nitrogen (N)- gases at RT
Bromine (Br), Mercury (Hg)- liquid at RT

6. Section 2.1: Classifying Matter
Elements: Symbols for Elements
Developed in 1813 by Swedish chemist Jons Berzelius
Symbols contain 1 or 2 letters
Symbols based on Latin names of the elements

7. Section 2.1: Classifying Matter
Compounds
Def.-a substance that is made from two or more simpler substances and can be broken down into those simpler substances (elements or other compounds)
H2O→2H + O

8. Section 2.1: Classifying Matter
Compounds
Properties of a compound differ from the properties of the substances from which it is made.
Ex. H and O are gases at room temp.; H2O is liquid at room temp.

9. Section 2.1: Classifying Matter
Compounds
Key Concept: A compound always contains two or more elements joined in a fixed proportion.
Ex. SiO2- 2 (O) atoms for every 1 (Si) atom
Ex. H2O-2 (H) atoms for every 1 (O) atom

10. Elements vs. Compounds
If you see the chemical formula for an element what do you notice? Pb K Li H2 O2
What is different on these formula’s of compounds?
H2O
CO2
C6H12O6
LiCl
NaCl

11. Section 2.1: Classifying Matter
Mixtures
2 types: heterogeneous and homogeneous
Retain some of the properties of their individual substances
Properties of a mixture are less constant (vary) than the properties of a substance.

12. Section 2.1: Classifying Matter
Mixtures
Key Concept: The properties of a mixture can vary because the composition of a mixture is not fixed.
**Mixtures can be classified by how well the parts of the mixture are distributed throughout the mixture.

13. Section 2.1 Classifying Matter
Mixtures: Heterogeneous and Homogeneous Mixtures
Heterogeneous- the parts of the mixture are noticeably different from one another
Ex. Sand
Homogeneous-the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another
Ex. Water, steel

14. Mixtures Heterogeneous Homogeneous
A mixture made up of particles that are uniformly distributed (means that you cant see the separate parts)
Ex. Salt water
In the ocean you cant see the salt dissolved in the water
A mixture made up of particles that are not uniformly distributed (normally you can easily see the separate parts)
Ex. Raisin Bran
You can see the Raisins, flakes, and the milk.

15. Section 2.1 Classifying Matter
Solutions, Suspensions, and Colloids
The size of the particles in a mixture has an effect on the properties of the mixture.
Key Concept: Based on the size of its largest particles, a mixture can be classified as a solution, a suspension, or a colloid.

16. Section 2.1 Classifying Matter
Solutions
Def.-the mixture that forms when substances dissolve and form a homogeneous mixture
Ex. Sugar water, salt water, lemonade

17. Section 2.1 Classifying Matter
Solutions
*They do not separate into distinct layers over time.
*They cannot be filtered.
*Light passes through them.
The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light.

18. Section 2.1 Classifying Matter
Suspensions
Def.-a heterogeneous mixture that separates into layers over time
Ex. Amoxicillin, muddy water

19. Section 2.1 Classifying Matter
Suspensions
*Suspended particles settle out of a mixture or are trapped by a filter
They scatter light in all directions because the particles are large; suspensions are cloudy.

20. Section 2.1: Classifying Matter
Colloids
Def.-a mixture that contains some particles that are intermediate in size between the small particles in solution and larger particles in a suspension
Ex. Milk, fog

21. Section 2.1 Classifying Matter
Colloids
Do not separate into layers
Cannot be filtered
Since they also contain larger particles, they scatter light

22. Section 2.2 Physical Properties
Examples of Physical Properties
Def.-any characteristic of a material that can be observed or measured without changing the composition of the substances in the material
Key Concept: Viscosity, conductivity, malleability, hardness, melting point, boiling point, and density are examples of physical properties.

23. Section 2.2: Physical Properties
Viscosity
Def.-the tendency of a liquid to keep from flowing (its resistance to flowing)
>viscosity, the slower the liquid moves
Ex. Corn syrup, honey (high viscosity)
Ex. Water (low viscosity)
Viscosity usually decreases when a liquid is heated.

24. Section 2.2 Physical Properties
Conductivity
Def.-a material’s ability to allow heat flow
Conductor-materials that have high conductivity (ex. Metals)
Ex. Poor conductor (wood)

25. Section 2.2: Physical Properties
Malleability
Def.-the ability of a solid to be hammered without shattering
Ex. Most metals are malleable; glass shatters (brittle)

26. Section 2.2: Physical Properties
Hardness
Ie. Can the material be scratched easily? Can it be cut easily?
Diamond is one of the hardest known materials (can cut glass and steel); aggregated diamond nanorods (hardest; carbon-60 molecules)
Stainless steel can scratch copper

27. Section 2.2 Physical Properties
Melting and Boiling Points
Melting pt.-the temp at which a substance changes from solid to liquid
Boiling pt.-the temp at which a substance boils

29. Section 2.2 Physical Properties
Density
Def.-the ratio of the mass of a substance to its volume
*can be used to test the purity of a substance
Ex. Density of silver=10.5g/cm3 RT
*if density of a coin is 9.9 g/cm3 RT then: 1.) the coin is not silver or 2.) the coin contains substances in addition to silver

30. Section 2.2 Physical Properties
Using Physical Properties
Key Concept: Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture.

31. Section 2.2 Physical Properties
Using Physical Properties: Using Properties to Identify Materials
Steps are similar to those used to test for purity
Decide which properties to test
Do tests on a sample of the unknown
Compare the results with the data reported for known materials
ID of materials can be crucial to solving a crime.

32. Section 2.2 Physical Properties
Using Physical Properties: Using Properties to Choose Materials
Properties determine which materials are chosen for which uses
What material is more durable? Is a material more comfortable?

33. Section 2.2 Physical Properties
Using Properties to Separate Mixtures
Some properties can be used to separate mixtures
Key Concept: Filtration and distillation are two common separation methods.

34. Section 2.2 Physical Properties
Using Properties to Separate Mixtures: Filtration
Filtration- a process that separates materials based on the size of their particles
small pass through; large are trapped

35. Section 2.2 Physical Properties
Using Properties to Separate Mixtures: Distillation
Def.-a process that separates the substances in a solution based on their boiling points
Ex. (making freshwater)-Water heated until in gas form; then cooled back to a liquid and collected in a separate container
Water has a lower boiling point than compounds dissolved in seawater.

36. Section 2.2 Physical Properties
Recognizing Physical Changes
Physical change-what occurs when some of the properties of a material change, but the substances in the material remain the same
Water (liquid→gas); Bending metal
Actions: slice, cut, heat
**Some physical changes are reversible, some are not (Cutting hair)

37. Section 2.3 Chemical Properties
Observing Chemical Properties
Chemical property-any ability to produce a change in the composition of matter
Key Concept: Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.

38. Section 2.3 Chemical Properties
Observing Chemical Properties: Flammability
Def.-a material’s ability to burn in the presence of oxygen
Not always a desired property: fabrics
Ex. Paper, fuels (highly flammable)

39. Section 2.3 Chemical Properties
Observing Chemical Properties: Reactivity
Def.-the property that describes how readily a substance combines chemically with other substances
Oxygen-high reactivity; Nitrogen-low reactivity
Ex. Oxygen causes iron to rust; rust is brittle and weaker than iron

40. Section 2.3 Chemical Properties
Recognizing Chemical Changes
Chemical change- what occurs when a substance reacts and forms one or more new substances
Key Concept: Three common types of evidence for a chemical change are a change in color, the production of a gas, and the formation of a precipitate.
Precipitate-any solid that forms and separates from a liquid mixture

41. Section 2.3 Chemical Properties
Is a Change Chemical or Physical?
Can be difficult to distinguish one from the other
Ask the question: Are different substances present after the change takes place? No-physical; Yes-chemical
Key Concept: When matter undergoes a chemical change the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.