Dear Readers,  Remember this is only the information needed to pass the AP exam, there is still a written portion. The written portion will feature problem solving, and that is an aspect of the exam that cannot be learned through my 23 day course.

Chemistry: An Overview

Two fundamental concepts of Chemistry: matter is composed of various types of atoms, and one substance changes to another by reorganizing the way the atoms are attached to each other. Scientific Method: 1) Making observations (collecting Data), 2) Making a prediction (formulating a hypothesis), 3) Doing experiments to test the prediction (testing the hypothesis)

The Scientific Method

There are actually many scientific methods, but the general framework for the process is 1) Making Observations. Observations may be qualitative (appearance, smell, etc.) or quantitative (temperature, calculations, etc.). Basically a qualitative observation doesn’t involve numbers, while a quantitative does. 2) Formulating a hypothesis. A hypothesis is a possible explanation for an observation. 3) Performing experiments. An experiment is used to test a hypothesis. Experiments will determine if the hypothesis is correct and bring forth new data.Theory: often called a model, is a set of tested hypotheses that gives an overall explanation for some natural phenomenon. (cant be proved)Robert Boyle: Did many experiments with cylinders and gas. He is most famously known for his experiments in pressure, and volume of gas. Wanted to destroy the idea of the elements as mystical substances (fire, earth, water, air) and wanted its new definition to be a substance that can’t be broken down any further. He was very important in modern chemistry.Natural Law: a statement that expresses generally observed behaviorLaw of conservation of mass: A natural law that is based on the common observation that the total mass of materials is not affected by a chemical change in those materialsDifference between law and theory is a law summarizes what happens; a theory (model) is an attempt to explain why is happens

Units of Measurement

A quantitative observation, or measurement, always consists of two parts: a number and a scale (called a unit)The two major systems of units are the English system used by the US, and a few other countries, and the Metric system used by the most of the rest of the industrialized worldSI system- a system of units which can be used internationally, mostly based on the metric system Prefixes: Are often used to be more convenient, ie. Centi, Milli, etc.Volume: a physical quantity, determines space.The fundamental SI Units: Mass- Kilograms (Kg), Length- Meter (m), Time- Second (s), Temperature- Kelvins (K), Electric current- Ampere (A), Amount of substance- mole (mol), Luminous intensity- candela (cd).Mass: A measure of the resistance of an object to a change in its state of motion. (measured by force necessary to move an object)Weight: amount of force gravity exerts on an object (note: Mass and weight are NOT the same)

Uncertainty in Measurement

When reading from a buret or other device to measure liquid, always read the meniscus, which is the bottom curve.The digits one is certain of in a measurement is the certain digits, and the digits that are about that number are uncertain digits. When reporting a number its all the certain digits with one uncertain digit.All measurements have some degree of uncertainty. It is important to report all answers in significant figures. (all certain digits and one uncertain)Accuracy: agreement of a particular value with its true value.Precision: degree of agreement among several measurements of the same quantity. Reflects the reproductability of a certain measurement. (different from accuracy)Random error (indeterminate error): equal probability of being low or high.Systematic error (determinate error): type of error occurs in the same direction each time. It is either always high or always low.

Significant Figures and Calculations

Rules for counting significant Figures: 1) Nonzero integers: Nonzero integers always count as significant figures. 2) Zeros. There are three classes of zeros: a) leading zero’s are zero’s that precede all the non zero digits. These do not count as significant figures. B)Captive zeros are zeros between non zero digits. These always count as significant figures. C) Trailing zeros are zeros as the right end of the number. These are significant only if the number contains a decimal point. 3) Exact Numbers: Have an infinite number of significant figures. Are numbers determined through counting.Rules of Significant figures in mathematical operations: 1) Multiplication/Division: The number of significant figures in the result is the same as the number in the least precise measurement used in the calculation. 2) Addition/Subtraction: the result has the same number of decimal places as the least precise measurement used in the calculation.Rules for Rounding. 1) In a series of calculations, carry the extra digits through to the final result, then round, 2)If the digit to be removed is less than 5 the preceding digit stays the same, and if it is greater than 5 the preceding digit is increased by 1. (Note: when rounding use only the first number to the right of the last significant figure)

Dimensional Analysis

Unit factor method (dimensional analysis): converting one system of units to another.Converting from One Unit to Another: 1) to convert from one unit to another, use the equivalence statement that relates the two units. 2) Derive the appropriate unit factor by looking at the direction of the required change (to cancel the unwanted units). 3) Multiply the quantity to be converted by the unit factor to give the quantity with the desired units.

Temperature

Three systems of measuring temperature used are the Celsius scale, the Kelvin Scale, and the Fahrenheit scale. The first two are used in physical sciences, the third in engineering.The Celsius and Kelvin scale have the same degrees scale, just add 273 to the Celsius degree to get Kelvin and vice-versa.

Density

Density is mass/volume.

Classification of Matter

Matter: anything occupying space and having mass.States: Matter exists in three states of solid, liquid, and gas. Solids are rigid fixed volumes and shapes (molecules tightly packed). Liquids have a definite volume but not a fixed shape(molecules still tightly packed but not as much as solid). Gas has no fixed volume or shape. They are compressible (loosely packed molecules).Mixtures: almost everyone around us is a mixture. A blend of pure substances.Homogeneous mixture: having visibly indistinguishable partsHeterogeneous mixture: having visibly distinguishable partsSolution: a homogeneous mixture.Pure substance: something with a constant composition.Physical changes: a change in the form of a substance (state), not in its chemical composition.Distillation: a process depending on differences in the volatility (how readily substances become gasses) of the components, is one of the most important methods for separating components of a mixture. (when you vaporize things out heat saltwater to separate salt and water)Filtration: a method of separation which is used when the mixture has a solid and a liquid.Chromatography: a method of separation involving two phases (states) of matter: a mobile phase and a stationary phase. The Stationary phase is a solid and a mobile phase is a liquid or gas.Paper chromatography: uses a strip of porous paper, such as filter paper, for the stationary phase.Compound: a substance with constant composition that can be broken down into elements by chemical processesChemical Change: a change in which a given substance becomes a new substance or substances with different properties and different composition.Elements: are substances that cannot be decomposed into simpler substances by chemical or physical means.The most fundamental elements in the world are made up of atoms which are made up of protons, neutrons, and electrons. Even those can be broken down into elementary particles called quarks.