1. Introduction to Chemistry

2. What is chemistry?
Chemistry is the study of the composition of substances and the changes those substances undergo.
Chemistry covers other sciences also such as physics, biology, geology, etc.

3. Pure Science VS Applied Science
Pure science is the accumulation of knowledge for the sake of learning.
Applied science focuses on the use of acquired knowledge –results in technology such as the cell phone, TV, medicine.

4. The experimental process includes:
Observations: this is where you note and record facts with your senses (looking at the world around you!) Using one or more of the senses to make observations.
Hypothesis: an educated guess based on observations and prior knowledge–.…an “If, then statement”.
Create an experiment – a test of the hypothesis
Develop a procedure for a reliable experiment
Perform the experiment
Record DATA and observations
Data is information gathered during an experiment.
Data can be quantitative or qualitative.
Quantitative – quantities such as measurements (cm, g, liters)
Qualitative – data collected that gives a description such as color, gas collected, odor.

5. The experimental process includes:
Analyze the data
Does your data support your hypothesis?
If yes, then Communicate the results….write a conclusion that summarizes your experiment.
If no, modify or change your hypothesis and start again.

6. Experiment Terminology
Operational definition – a statement that details how a particular variable is to be measured or how a term is to be defined.
Variable –any factor in an experiment that can change.
Control group –group that is NOT tested
Experimental group –group that is being tested
Control or constant variable –factors that stay the same in both control group and the experimental group
Analysis –finding meaning data by looking at patterns or trends
Independent variable (manipulated variable)–variable being tested
Dependent variable (responding variable) –the effect of the independent variable

7. Theory & Law
Theory – a thoroughly tested model that explains why experiments give certain results. This means the results are the same over and over again…no matter when or where the experiment is conducted. The hypothesis has withstood testing.
Law – a concise statement (usually mathematically like a formula) that summarizes the results of a broad variety of observations and experiments. **It may take several different experiments to come up with a law. Examples of laws:
E = mc2
P = 1 / V

8. Matter
Matter is all the substances around us. It’s anything that takes up space and has mass.
Forms of matter:
Solid – state of matter that has definite shape and volume
Liquid – state of matter that has definite volume but no definite shape
Gas –state of matter that has neither definite shape nor volume
How can we measure matter? By using mass –which is the measure of the quantity of matter.
Mass is not affected by 1) temperature 2) location on earth 3) gravity
What is the difference between mass and weight? Weight is the measure of force of gravitation (gravitational attraction) between the earth and an object. Weight can change according to location on earth (or another planet!).

9. Matter MATTER: elements, compounds, mixtures
The first two kinds of matter-
1) elements Ex: Cu, I, Fe, O – a substance that cannot be broken down into other substances. Elements are respresented by one or two letters called symbols. The smallest particle of an element that has all the properties of that element is an atom.
2) compounds – chemical combinations of 2 or more elements –these can be broken down into their components EX: HCl and NaOH. Compounds can be represented by the combination of letters/symbols called a formula. The smallest particle of a compound that has the properties of that compound is called a molecule.
Samples of elements and compounds, wherever they may be found, are always the same (as long as there are no impurities).
Because of this consistency (of being the same everywhere) both elements and compounds are called substances

10. Elements
There are over 100 elements in existence. Some are found in nature and some are made in the laboratory –these are called synthetic or man made.

11. Compounds
Characteristics of compounds: 1) combined in a definite ratio 2) chemical and physical properties of a compound differ from those of the elements that make them up. 3) compounds can be formed from simpler substances and decomposed into simpler substances.
When compounds break down, what do they form?
Elements MgO ----- Mg + O2
Elements & compounds NaOH -- Na + H2O

12. Mixtures Mixtures are the third type of matter.
A mixture consists of two or more substances where each retains its individual properties EX: rock, salty water, air   
Mixtures form in 3 ways:
An element is mixed with one or more elements (nonreactive –no chemical activity)
A compound is mixed with one or more other compounds.
One or more elements are combined with one or more compounds.
Substances mix with other substances but a chemical combination does not occur—mixtures are only physical combinations.
Mixtures can be any state: solid, liquid, gas.

13. Mixtures, contd
An element or compound has one set of properties but a mixture retains the properties of its constituents.
 The composition of an element or compound is fixed; the composition of a mixture can vary widely.
 Mixtures can be homogeneous or heterogeneous. Homo =means the same throughout. (Solutions are homogeneous mixtures). Hetero = means different composition.

14. Properties
By use of properties, we recognize something – a set of characteristics that make it recognizable.
 Physical properties describe: 1) what can be observed by examining the substance and 2) the way it behaves when brought in contact with other substances or exposed to sources of energy
 Examples of physical properties: color, taste, odor, density, state: solid, liquid, gas; solubility, flammability, melting point, boiling point, reactivity, malleability, ductility, elasticity, hardness, conductivity, etc.

15. Know these property definitions
Odor is a property of matter that can be detected by sniffing.
Malleability is a property that allows some metals to be hammered into sheets.
Ductility is a property that allows some metals to be drawn into thin wires.
Density is mass per unit volume of a substance. (Volume is the amount of space a substance occupies.)

16. Elasticity is the ability of some materials to return to their original shape after being stretched.
Solubility is the ability of some forms of matter to be dissolved in other forms such as liquids.
Taste is the property of matter associated with eating food.
Hardness is a property of all matter that refers to a substance’s ability to resist scratching.

17. Conductivity is the ability of some types of matter, especially metals, to transmit heat or electricity.
Melting Point is the temperature at which a type of matter in the solid state becomes a liquid.

18. Physical Change vs Chemical Change
A physical change will alter the substance without changing it composition.
Chemical changes occur when a substance undergoes a change so that one or more new substances are formed.
Indicators of chemical change
Smell
Color Change
Gas formation

19. Law of Conservation of Mass/Energy
The Law of Conservation of Mass/Energy, as proposed by Antoine Lavoisier, governs all chemical changes. All reactions must obey this law. Formally stated: Mass/Energy cannot be created nor destroyed in a chemical reaction. So it is saying that the mass of the reactants must be the same as the mass of the products. In final words: what goes into a reaction must come out of the reaction (in terms of mass).