1. Classifying Materials
Unit #2

2. Matter
Def: anything that takes up space and has mass

3. States of Matter Liquid Solid Flows (takes the shape of its container)
Has definite shape and volume
Particles are tightly packed and locked in place (incompressible)
Not defined by rigidity or hardness
Liquid
Flows (takes the shape of its container)
Indefinite shape
Constant/Definite volume
Expands when heated
Virtually incompressible
Takes the shape of the container
Particles are less closely packed; can move past each other

4. States of Matter cont. Gas Flows
Takes the shape AND volume of the container (Indefinite shape and volume)
Particles are spaced far apart and easily compressed
Vapor
Substance in the gaseous state that is a solid or a liquid at room temperature
Example: steam

5. States of Matter with Named Changes

6. Substances
Def: Matter that has a uniform and unchanging composition (pure substance)
Examples
Table Salt: always sodium and chloride
Water: always hydrogen and oxygen
NOT sea water…why not?

7. Pure Substances
Def: matter that has a uniform and unchanging composition
Two types:
Elements
Cannot be separated into simpler substances
Contain all the same atoms
Ex: C, Al, Cu, Hg, Au

8. Elements 92 naturally occurring on Earth Unique name and symbol
Dmitri Mendeleev organized 1st periodic table
Periods = horizontal rows
Groups or families = vertical rows

9. Pure Substances cont. Compounds Combination of 2 or more elements
Can be broken down into elements by a chemical reaction
Ex: H2O, NaCl, CO2, etc.
Properties of elements are different than when they form compounds
Molecules – smallest particle of a compound or element

11. Mixtures
Def: a combination of two or more pure substances in which each pure substance retains its individual chemical properties
Two Types of Mixtures:
Heterogenous
Homogenous

12. Heterogeneous Mixture
Mixture that is not completely uniform
Individual substances remain distinct

13. Homogeneous Mixture Mixture that is uniform throughout
Particles are evenly mingled
aka Solutions –
Def: homogeneous mixture of 2 or more substances
Contain very small particles
Solvent – dissolving agent (usually a liquid)
Solute – substance being dissolved (usually a solid)
Aqueous solution – any solution whose solvent is water
Examples:
Salt and water
Air – mixture of gases
Alloys

14. Homogeneous Mixture - Alloy
Def: A homogenous mixture of metals, or a mixture of one metal and one nonmetal, in which the metal substance is the major component
Used by manufactures to achieve greater strength and durability
Used in spacecrafts and automobiles

15. Techniques Used for Separation
Filtration
Separates a liquid from a solid (heterogeneous mixtures)
Distillation
Physically separates most homogeneous mixtures based on boiling point differences of the substances
Crystallization
Produces pure solid particles of a substance from a solution that contains the dissolved substance
Chromatography
Separates components of a mixture on its ability to travel or be drawn across the surface of another material

17. Joseph Proust (France 1799)
Law of Definite Proportions:
A given compound always contains elements in a certain proportion by mass. (Constant composition).

18. Law of Definite Proportions
Atoms combine in whole number ratios, so their proportion by mass will always be the same.
Example: H2O is always made up of 2 atoms of H and one atom of O.
The ratio of O to H in water is always ( : ) which is 16:2 or 8:1.

19. Example Law of Definite Proportions :
KCl always contains one atom of K for every one atom of Cl
In KCl, potassium and chlorine always have a ratio of ( to ) or ~1:1 by mass.

20. Law of Definite Proportions
Formula:
Percent by mass (%) = mass of element x 100
mass of compound

21. Example
A compound of sucrose is made up of the elements carbon, hydrogen, and oxygen. Carbon makes up 8.44 grams, hydrogen makes up 1.30 grams, and oxygen makes up grams. Find the percent by mass of each of the elements in the compound.

22. Law of Definite Proportions
Percent by mass (%) = mass of element x 100
mass of compound
Law of Definite Proportions
Column 1
Column 2
Element
Analysis by mass (g)
Percent by mass (%)
Carbon
8.44 g carbon
8.44 g Carbon x 100
20.00 g Sucrose = 42.20% Carbon
Hydrogen
1.30 g hydrogen
1.30 g Hydrogen x 100
20.00 g Sucrose = 6.50% Hydrogen
Oxygen
10.26 g oxygen
10.26 g Oxygen x 100
20.00 g Sucrose = 51.30% Oxygen
Total
20.00 g sucrose
= 100%

23. Law of Multiple Proportions (John Dalton)
When the same two elements combine to form more than one compound:
the ratios of the mass of one element in the first compound to its mass in the second compound, (as it combines with the same mass of the other element), can always be expressed as ratios of small whole numbers( ex: 1:3 or 2:5).
Example
Water (H2O) = 2:1 Hydrogen to Oxygen
Peroxide (H2O2) = 2:2 Hydrogen to Oxygen

24. Example of Law of Multiple Proportions
Carbon combines with oxygen to form CO and CO2 .
Mass of Carbon(g)
Mass of Oxygen(g)
Ratio of O in CO2 to O in CO CO
12.01
16.00
CO2
32.00
2:1

25. Example
In the carbon compounds ethane (C2H6) and ethene (C2H4), what is the lowest whole number ratio of H atoms that react with the same number of C atoms?
Answer: 3:2

26. Physical Changes
Def: Change that alters at least one of the physical properties of the substance
Does not change the chemical composition
Examples:
Changing the physical state – i.e. freezing, melting, etc.
Dissolving
Altering the shape or size

27. Physical properties
Def: Observed or measured without changing the chemical composition or identity of the substance
Intensive
Doesn’t depend on the amount of the substance
Always remain the same for a given substance
Ex: melting point, boiling point, density
Extensive
Depends on how much matter is being considered
Ex: mass, volume, size
Also, properties that can change for a substance
Ex: color, state, shape

28. Chemical changes
Def: a change in the chemical composition of a substance (cannot go back to original form)
Occurs as a chemical reaction
Examples:
Iron rusting to form iron (III) oxide
Fermentation of grape juice

29. Chemical properties
Def: the ability of a substance to undergo chemical reactions and to form new substances
Examples:
Rusting is a chemical property of iron
Ability to rot, rust, decompose, ferment, corrode, grow, and decay
Physical changes indicate a chemical change has occurred
Ex: heat, light, flame, gas bubbles, changes in color, formation of a solid, etc.

30. Law of Conservation of Mass
Def: States that mass is neither created nor destroyed during a chemical reaction; it is CONSERVED
Mass reactants = Mass products
H O2 H2O
reactants products
Total mass started is the same at the end