AP Chemistry Chapter 1 – Chemical Foundations
1.1 Chemistry: An Overview ______
-Atoms cannot be seen with the naked eye but a special microscope called the scanning tunneling microscope (STM) can be used to “see” individual atoms.
Reference Figure 1.1 (pg 3)
-We live in a macropscopic world. Scientists delve into this macroscopic world to discover it’s parts. For example, sand on a beach from a distance looks uniform, but close up the irregular sand grains are visible, and each grain is composed of tiny atoms of silicon and oxygen bonded forming intricate shapes.
1.2 The Scientific Method______
-The process of scientific inquiry consists of the fundamental components:
1. Making observations (collecting data)
2. Suggesting a possible explanation (formulating a hypothesis)
3. Conducting experiments to test the possible explanation (testing a hypothesis)
-Once a set of hypotheses agrees with various observations as an overall explanation of some natural phenomenon a theory (also called a model) is formed. A theory is a human invention and is an interpretation.
-A natural law summarizes an observation of what happens, a theory is an attempt to explain why it happens.
-The law of conservation of matter is an example of a natural law. Matter is neither created not destroyed but transferred.
1.3 Measurements_& 1.4 Uncertainty in Measurement ______
-Chemistry is a quantitative science. Measurements and data are used to draw conclusions.
-Two major systems are used, the English system (used in the US) and the metric system used by most of the industrialized world.
-In 1960 an international agreement set up a system of units called the International System or SI units (le System International in French).
Reference Table 1.1 (pg 9)
-Instruments & Units
- Length – SI unit meters (m)
- Volume – SI unit liters (L)
- Mass – SI unit kilograms (kg)
- Temperature – SI unit Kelvin (K)
-Significant figures allow us to cite a degree of confidence in a measurement by understanding that there is an uncertainty of at least one unit in the last digit of that measurement.
-The certainty of a measurement must be determined based on the instrument being used to measure.
-Two terms are used to describe the reliability of a measurement, precision and accuracy.
-Accuracy refers to the agreement of a particular value with a true or accepted value.
-Precision refers to the degree of agreement among several measurements of the same quantity.
-A measurement that is precise but not accurate indicates small random errors (poor technique) but a large systemic error (for example a balance not zeroed correctly).
Reference Figure 1.8 (pg 13)
1.5 Significant Figure Calculations & 1.6 Dimensional Analysis______
-Rules for counting sig figs:
1. Nonzero integers always count as significant.
2. Leading zeros never count as significant.
3. Captive (middle) zeros always count as significant.
4. Trailing zeros only count as significant when there is a decimal point visible in the measurement.
5. Exact numbers are said to have infinite significant figures therefore are not counted. Numbers determined by counting fall under this category. For example, 10 people or 3 apples. Also, certain measurement conversion factors are considered to be exact such as 1 in = 2.54 cm and are not counted in sig figs.
Reference pg 14
-Calculations using sig figs:
- Multiplication/Division – least amount of sig figs
- Subtraction/Addition – least amount of decimal places
-If the same rule is applied throughout one problem then rounding the answer is done at the end. If different operations are required for one problem than order of operations must be applied and rounding of the answer must be done before applying a new sig fig rule.
-Converting from one unit to another in chemistry is done by using the unit factor label (also called conversion facto label) method, commonly referred to as dimensional analysis.
- It is important to use units as a guide to the answer. It is also crucial to know metric prefixes in order to convert (reference table 1.2 – page 8)
Reference Table 10.2 (pg10)
1.7 Temperature ______
-Three systems for measuring temperature are commonly used: Celsuis, Kelvin, and Fahrenheit.
-The size of the temperature unit (the degree) is the same for the Celsius and Kelvin scale, however their zero point are not the same. The adjustment for this is simple:
To convert degrees Celsius to Kelvin units: TK = ToC + 273.15
Or subtract 273.15 from the Kelvin temperature to get the Celsius temp.
-Converting between the Fahrenheit and Celsius scales is a little more complicated because not only are the zero points not the same but the degree amounts are also different. The following formulas maybe used to convert from one to the other as they adjust for the degree (9/5 or 5/9) and zero point difference (a difference of 32):
Fahrenheit to Celsius: ToF = ToC 9oF + 32
5oC
Celsius to Fahrenheit: ToC = (ToF – 32) 5oC
9oF
Reference Figure 1.9 (pg 21)
1.8Density ______
-Properties of a substance may be used to identify it. Properties used to identify a substance must be independent of the amount (intensive) unlike properties such as volume or mass which are extensive.
-Types of properties:
- Physical – observed without changing the chemical identity of a substance.
- Density – a ration of mass per unit volume
- Solubility – the extent to which a solute dissolves in a solvent. This unit is expressed in terms of grams of solute per 100 grams of solvent (generally water) and is specific to a temperature.
- Saturated
- Unsaturated
- Supersaturated
- Chemical – observed only when the identity of a substance is changed.
1.9 Classification of Matter ______
-Matter is anything that has mass and occupies space.
-There are 3 common state of matter: solid, liquid, & gas.
Solid = definite shape and definite volume
Liquid = indefinite shape and definite volume
Gas = indefinite shape and indefinite volume
-Any change between the state of matter is always a physical change.
-Three main classifications of matter (Keep in mind elements & compounds are both pure substances):
ElementsCompoundsMixtures
CovalentHeterogeneous
IonicHomogeneous
Common Lab Instruments & Techniques______
-Measuring volume:
Graduated cylinder
Volumetric pipet
Buret
Volumetric Flask
Reference Figure 1.6 (pg 11)
-Filtration – used to separate a heterogeneous mixture
Funnel and filter paper
-Decantation – used to separate precipitate from solution
Beaker and stirring rod
-Distillation – used to separate a homogeneous mixture using the volatility of a substance
Distillation apparatus
Reference Figure 1.12 (pg 27)
-Chromatography – also used to separate homogenous mixtures
Think Layer Chromatography (TLC)
Gas-Liquid Chromatography (GL)
Reference Figure 1.13 (p 28)
Color: Absorption Spectrum - colors of gases and liquids are due to the selective absorption of certain components of visible light. The wavelengths of visible light range from 400 – 700nm. For example potassium permanganate gives off a purple color because it absorbs at approximately 550nm.
Spectrophotometer
Colorimeter
Textbook Assignments