1. Properties & Changes of Matter
Unit 2

2. Matter
Anything with mass & volume
All matter is composed of atoms

3. Two Types of Matter
Pure substance – definite and uniform characteristics
Every sample is the same
Identified by density, atomic structure, etc.
Mixture – contains 2 or more pure substances
Can vary in composition & properties

4. Pure Substances 1. Elements – contain only one kind of atom
Monatomic – exists as single atom
Diatomic – two atoms joined together

5. Pure Substances 2. Compounds – Composed of more than one kind of atom
Can only be broken down by chemical means
Represented by formulas

6. Law of Definite Proportions
Compound is always composed of the same elements in the same proportion by mass
Sodium Chloride
39.3% Na & 60.7% Cl
Density, atomic structure ID

7. Mixtures Contain two or more pure substances
Can be separated by physical means
Homogeneous – uniform composition
Often called a solution
Crystal Light in water
Stainless steel
Fountain drinks

8. More on Solutions (Homogeneous)
A solution is made by dissolving SOLUTES in a SOLVENT
Water is the universal solvent
Colloids – appears to be a solution but really is a heterogeneous mixture
Milk, asphalt, paint

9. Mixtures Heterogeneous – non-uniform composition Oil and water
Trail mix
This class!

10. Separating a Mixture - Distillation

11. Separating a Mixture - Filtration

12. Separating a Mixture - Chromatography

13. Physical Properties of Matter
Conditions or qualities that can be observed or measured without changing the composition of a substance

14. Examples of Physical Properties
Density – ratio of mass to volume
Conductivity – ability to conduct electricity or heat
Malleability – ability to be deformed without cracking
State of Matter

15. States of matter Solid – fixed volume & shape
Liquid – Fixed volume, takes shape of its container
Gas – no fixed volume or shape
Vapor – currently a gas but normally a solid or liquid
Plasma – particles broken apart & charged

16. States of Matter Definite Volume? Definite Shape?
Intermolecular forces (IMFs)
Strong –
Little molecular movement
Solid
YES
YES
Less strong –
Slow molecular movement
Liquid NO
YES
Weak –
Fast molecular movement
Gas NO NO

17. Physical Changes Identity of substance doesn’t change
Key words - boil, freeze, melt, break, crush, tear, split, grind, cut, condense
Examples
Dissolving sugar in water
Crushing or breaking rock
Changes in state of matter

18. Condense
Freeze
Melt
Evaporate
Solid
Liquid
Gas

19. Deposition Sublimation Liquid Gas Solid
Freeze Drying = Sublimation; Skips liquid phase to allow stability & aesthetics by alter temp & pressure
Solid
Liquid
Gas

20. Physical Changes
State of matter changes can also be caused by pressure
Different states of matter have different energy contents

21. Phase Changes of Water

22. Chemical Properties of Matter
Reactivity – tendency of an element to enter into a chemical reaction

23. Chemical Changes of Matter
Results in the creation of a new substance
AKA a chemical reaction
Represented by a chemical equation
Reactants  products
H2O + CO2  C6H12O6 + O2

24. Evidence of Chemical Changes
Evolution/production of a gas
Bubbling or odor change
Forming a precipitate
Two clear solutions  cloudy/particles
Release or absorb energy
Change temperature or give off light
Color change in reaction system

25. Chemical Changes Not easily reversed End product has new properties!
Key words – burn, rot, rust, decompose, ferment, explode, corrode

26. Law of Conservation of Mass
Lavoisier
In a chemical reaction, the mass of the products is equal to the mass of the reactants
223.4 g Fe g O2  g Fe2O3
Mass is not created or destroyed in ordinary reactions