Chemistry - the study of matter and the changes it undergoes Matter - anything that has mass and occupies space

Atoms vs. Molecules Matter is composed of tiny particles called atoms. Atom: smallest part of an element that is still that element. Molecule: Two or more atoms joined and acting as a unit.

A Chemical Reaction One substance changes to another by reorganizing the way the atoms are attached to each other.

Science Science is a framework for gaining and organizing knowledge. Science is a plan of action — a procedure for processing and understanding certain types of information. Scientists are always challenging our current beliefs about science, asking questions, and experimenting to gain new knowledge. Scientific method is needed.

Fundamental Steps of the Scientific Method

Nature of Measurement Measurement Quantitative observation consisting of two parts. number scale (unit) Examples 20 grams 6.63 × 10-34 joule·second

The Fundamental SI Units Physical Quantity Name of Unit Abbreviation Mass kilogram kg Length meter m Time second s Temperature kelvin K Electric current ampere A Amount of substance mole mol Luminous intensity candela cd

Derived Units Quantity symbol unit name unit derivation Area A square meters m2 A = l X w Volume V cubic meters m3 V = l X w X h Density d grams per mL g/mL d = m/V Molar mass MM grams per mole g/mol MM = m/n Concentration c moles per liter M M = mol/V Molar volume Vm liters per mole L/mol Vm = V/mol

Prefix Symbol Meaning Scientific Notation tera- T 1,000,000,000,000 1012 giga- G 1,000,000,000 109 mega- M 1,000,000 106 kilo- k 1,000 103 base none 1 100 centi- c 0.01 10-2 milli- m 0.001 10-3 micro- μ 0.000 001 10-6 nano- n 0.000 000 001 10-9 pico- p 0.000 000 000 001 10-12 femto- f 0.000 000 000 000 001 10-15

Different measuring devices have different uses and different degrees of accuracy.

Measurement of Volume Using a Buret The volume is read at the bottom of the liquid curve (meniscus). Meniscus of the liquid occurs at about 20.15 mL. Certain digits: 20.15 Uncertain digit: 20.15

What is the volume? 17 mL 17.5 mL 17.49 mL 17.50 mL 17.500 mL

Precision and Accuracy Accuracy - Agreement of a particular value with the true value. Precision - Degree of agreement among several measurements of the same quantity.

Rules for Counting Significant Figures There are 5 guidelines to follow when determining the number of significant figures in a measured quantity (underline shows sig fig) 1. All nonzero digits are significant. 457 2.5 2. Zeroes between two significant figures are themselves significant. 1.03 3. Zeroes at the beginning of a number are never significant. 0.02 4. Zeroes at the end of a number are significant if a decimal point is written in the number. 0.0200 5. Exact numbers have an infinite amount of significant digits. 10 moleucles

The Atlantic /Pacific Rule For Determining Significant Digits Pacific – "P" is for decimal point is present. If a decimal point is present, count significant digits starting with the first non-zero digit on the left and continue to the right) Examples: (a) 0.004703 has 4 significant digits. (b) 18.00 also has 4 significant digits. Atlantic – "A" is for decimal point is absent. If there is no decimal point, start counting significant digits with the first non-zero digit on the right and continue to the left. (a) 140,000 has 2 significant digits. (b) 20060 has 4 significant digits.

Exponential Notation Example 300. written as 3.00 × 102 Contains three significant figures. Two Advantages Number of significant figures can be easily indicated. Fewer zeros are needed to write a very large or very small number.

Significant Figures in Mathematical Operations 1. For multiplication or division, the number of significant figures in the result is the same as the number in the least precise measurement used in the calculation. 1.342 × 5.5 = 7.381  7.4

Significant Figures in Mathematical Operations 2. For addition or subtraction, the result has the same number of decimal places as the least precise measurement used in the calculation.

CONCEPT CHECK! You have water in each graduated cylinder shown. You then add both samples to a beaker (assume that all of the liquid is transferred). How would you write the number describing the total volume? 3.1 mL What limits the precision of the total volume? The total volume is 3.1 mL. The first graduated cylinder limits the precision of the total volume with a volume of 2.8 mL. The second graduated cylinder has a volume of 0.28 mL. Therefore, the final volume must be 3.1 mL since the first volume is limited to the tenths place.

Use when converting a given result from one system of units to another. To convert from one unit to another, use the equivalence statement that relates the two units. Derive the appropriate unit factor by looking at the direction of the required change (to cancel the unwanted units). Multiply the quantity to be converted by the unit factor to give the quantity with the desired units.

Example #1 A golfer putted a golf ball 6.8 ft across a green. How many inches does this represent? To convert from one unit to another, use the equivalence statement that relates the two units. 1 ft = 12 in The two unit factors are:

Example #1 A golfer putted a golf ball 6.8 ft across a green. How many inches does this represent? Derive the appropriate unit factor by looking at the direction of the required change (to cancel the unwanted units).

Example #1 A golfer putted a golf ball 6.8 ft across a green. How many inches does this represent? Multiply the quantity to be converted by the unit factor to give the quantity with the desired units.

Example #2 An iron sample has a mass of 4.50 lb. What is the mass of this sample in grams? (1 kg = 2.2046 lbs; 1 kg = 1000 g)

CONCEPT CHECK! What data would you need to estimate the money you would spend on gasoline to drive your car from New York to Los Angeles? Provide estimates of values and a sample calculation. This problem requires that the students think about how they will solve the problem before they can plug numbers into an equation. A sample answer is: Distance between New York and Los Angeles: 3200 miles Average gas mileage: 25 miles per gallon Average cost of gasoline: $2.75 per gallon (3200 mi) × (1 gal/25 mi) × ($2.75/1 gal) = $352 Total cost = $350

Dimensional Analysis practice The distance between the earth and the moon is 240,000 mi. What is this in meters? If the Concorde (which travels at 2400 km/hr) could fly to the moon, how many seconds would it take? How many seconds will we enjoy in AP chemistry class this year?

Always ask yourself whether your answer makes sense

The Three Major Temperature Scales

Converting Between Scales

At what temperature does °C = °F? EXERCISE! At what temperature does °C = °F? The answer is -40. Since °C equals °F, they both should be the same value (designated as variable x). Use one of the conversion equations such as °C = (°F-32)(5/9), and substitute in the value of x for both °C and °F. Solve for x.

EXERCISE! Since °C equals °F, they both should be the same value (designated as variable x). Use one of the conversion equations such as: Substitute in the value of x for both TC and TF. Solve for x.

EXERCISE!

Mass of substance per unit volume of the substance. Common units are g/cm3 or g/mL.

A certain mineral has a mass of 17. 8 g and a volume of 2. 35 cm3 A certain mineral has a mass of 17.8 g and a volume of 2.35 cm3. What is the density of this mineral? What is the mass of a 49.6-mL sample of a liquid, which has a density of 0.85 g/mL? A spherical ball of lead has a diameter of 5.0 cm. What is the mass of the sphere if lead has a density of 11.34 g/cm3?

Density is an intensive physical property of a substance. Determines if an object sinks or floats Helium balloons can float in air because helium is less dense than air, not because it is “lighter” than air. A cube of ruthenium metal 1.5 cm on each side has a mass of 42.0 g. Will this sample float on water? © 2009, Prentice-Hall, Inc.

Pure Substance A sample of matter with a fixed composition and distinct properties. It can be an element or a compound (only one component) Compounds can be decomposed by chemical processes Mixtures Combination of 2 or more substances in which each retains their own chemical identity (and therefore properties) Can be homogeneous or heterogeneous Can be decomposed by physical processes

The Organization of Matter

Physical Change Change in the form of a substance, not in its chemical composition. Example: boiling or freezing water Can be used to separate a mixture into pure compounds, but it will not break compounds into elements. Filtration Distillation Chromatography

Filtration  the process of passing a liquid or gas, such as air, through a filter in order to remove solid particles. Works for heterogeneous mixtures © 2009, Prentice-Hall, Inc.

Distillation The evaporation and subsequent collection of a liquid by condensation as a means of purification Distillation is used to separate chemical species by taking advantage of the differential strength of intermolecular interactions between and among the components. Simply put, if a solution of two or more liquids is being distilled, then it is the differences in their boiling points that makes the separation possible. Used to separate homogeneous mixtures

Chromatography Several types: paper, column, gas All types work by moving the mixture along a stationary material. The differential strength of intermolecular interactions between the component of the mixture and the stationary phase among the components cause the different components to move through at a different speed. http://chemsite.lsrhs.net/FlashMedia/html/paperChrom.html © 2009, Prentice-Hall, Inc.

Column Chromatography http://chemsite.lsrhs.net/FlashMedia/html/columnChrom.html

Here is a chromatogram that took 30 minutes to produce in a gas chromatograph. It shows peaks for each of the different chemicals. The peaks were measured by a simple detector that can't tell the difference between molecules, but it can give you an approximate measure of the quantity of molecules in the gas as it exits the GC. It doesn't directly tell you which molecule accounts for each peak, but under the same conditions, a particular chemical will always show a peak at the same time.

Chemical Change A given substance becomes a new substance or substances with different properties and different composition. Example: Bunsen burner (methane reacts with oxygen to form carbon dioxide and water)

Which of the following are examples of a chemical change? CONCEPT CHECK! Which of the following are examples of a chemical change? Pulverizing (crushing) rock salt Burning of wood Dissolving of sugar in water Melting a popsicle on a warm summer day 1 (burning of wood)