Introduction to Chemistry Unit 1 Introduction to Chemistry

What is Chemistry? Study of the ______________ of matter and the changes ______________ undergoes.

Scientific Method An important scientific discovery may involve some luck, but one must be prepared to recognize the lucky event. Alexander Fleming Most advances in science involves little or no luck, but a logical systematic approach to the solution of a difficult problem.

Scientific Method Logical approach to the solution of _______________________. Related to ordinary common sense.

Observation Using your ______________ to obtain information directly.

Hypothesis A possible ______________ or reason for what is observed.

Experiment Test the ______________. For the results of an experiment to be accepted, the experiment must produce the same result no matter how many times it is repeated, or by whom.

If the experimenting does not support the hypothesis, the hypothesis must be ______________. The process of testing the hypothesis must be carried out until the hypothesis fits all the observed experimental facts.

Theory Once a scientific hypothesis meets the test of repeated experimentation, it may become a ______________. A theory is a broad and extensively tested explanation of why experiments give certain results.

A theory can never be proved because it is always possible that a new experiment will disprove it. Theories give you the power to predict the behavior of natural systems.

Scientific Law Concise ______________ that summarizes the results of many observations and experiments. Describes a natural phenomenon without attempting to explain it. Can be expressed as a ______________ equation.

A law states what happens; a theory explains why.

Macro vs. Micro ______________ - things you see with the unaided eye or large scale experimenting. ______________ - things too small to see with the unaided eye - or small scale experimenting.

International System of Units The Metric System

Metric System The metric system was developed in France in the 1790s. The metric system missed being nationalized in this country by one vote in the late 1700s.

Metric System Based on the powers of 10.

Between each step, there is an increase by a power of 10. 10 mm = 1 cm 10 cm = 1 dm 10 dm = 1 m 10 m = 1 dam 10 Dm = 1 hm 10 Hm = 1 km

Yotta Y 1024 Zetta Z 1021 Exa E 1018 Peta P 1015 Tera T 1012 Giga G 109 Mega M 106 Kilo k 103 Basic Unit 1 Milli m 10-3 Micro  10-6 Nano n 10-9 Pico p 10-12 Femto f 10-15 Atto a 10-18 Zepto z 10-21 Yocto y 10-24

Units of Length SI unit = ______________ (m) 1 meter = 1000 mm 1 meter = 1.09 yards = 39.36 inches 1 km = 1000 meters 1 km = 0.62 miles 1 inch = 2.54 cm

Units of Volume Space occupied by any sample of matter. SI unit = m3 More common unit = ______________ (L) 1 L = 1000 mL 1 mL = 1 cm3

Units of Volume Unit of volume for a solid 1 mL = ______________ length x width x height = volume of a regular shaped object (cm3) 1 mL = ______________ One liter is a little more than a quart One cup is 250 mL

Units of Mass ______________ - measure of the quantity of matter in an object. ______________ - force that measures the pull of gravity on any given mass. SI unit = kilogram (kg) 1 kg = 1000 grams (g) 1 kg = 2.12 pounds One gram is about the mass of a paperclip

Units of Temperature Kelvin Scale – used when dealing with gases. 0 K = -273C Degree Celsius (°C) 0°C = 32°F (freezing point of water) 100°C = 212°F (boiling point of water)

Conversion between Temperatures F to C (C x 1.8) + 32 = F C to F (F – 32)  1.8 = C

Time SI Unit = ______________ (s)

Density Measure of ______________ per unit of ______________. Specific for every substance. Density = mass ÷ volume Unit of density = g/mL or g/cm3

Graphing

Graphing The relationship between two variables in an experiment is often determined by graphing the experimental data. The graph is a “______________” of the data.

Graphing Information ______________ Variable manipulated variable X-axis (horizontal) responding variable Y-axis (vertical)

Time (seconds) Distance (meters) 5 3.5 10 6.2 15 10.1 20 17.3 25 26.5 30 37.1

Scientific Measurement

Types of Measurements ______________ measurements - results are given in descriptive, non-numerical form. ______________ measurements - results are given in definite form, usually as numbers and units.

Scientific Notation A number written as the product of two numbers: a coefficient and 10 raised to a power. 3.6 x 105 The coefficient is always written as a number greater than one and smaller than ten - only one number to the left of the decimal.

Multiplication & Division In multiplication of scientific notation values, multiply the coefficients and add the exponents. In division of scientific notation values, divide the coefficients and subtract the exponents.

Addition & Subtraction Before adding or subtracting, the exponents must be the same. After the exponents are the same, add or subtract the coefficients with the 10 raised to the power of.

Significant Figures It is important to be honest when reporting a measurement, so that it does not appear to be more accurate than the equipment used to make the measurement allows. We can achieve this by controlling the number of digits, or _____________ _____________, used to report the measurement.

Rule 1: All nonzero digits are significant.

Rule 2: Zeros within a number are always significant. Both 4308 and 40.05 contain four significant figures.

Rule 3: Zeros that do nothing but set the decimal point are not significant. Thus, 470,000 has two significant figures.

Rule 4: Trailing zeros that aren't needed to hold the decimal point are significant. For example, 4.00 has three significant figures.

How many sig figs? (a) 0.0030 L (d) 0.00004715 m (b) 0.1044 g (e) 57,600 s (f) 0.0000007160 cm3 (c) 53,069 mL

Rules for Sig Figs in Answers When combining measurements with different degrees of accuracy and precision, the accuracy of the final answer can be no greater than the least accurate measurement. This principle can be translated into a simple rule for addition and subtraction: When measurements are added or subtracted, the answer can contain no more decimal places than the least accurate measurement.

Addition & Subtraction Example: adding two volumes 83.5 mL + 23.28 mL 106.78 mL = 106.8 mL Example: subtracting two volumes 865.9 mL - 2.8121 mL 863.0879 mL = 863.1 mL

Rules for Sig Figs in Answers The same principle governs the use of significant figures in multiplication and division: the final result can be no more accurate than the least accurate measurement. In this case, however, we count the significant figures in each measurement, not the number of decimal places: When measurements are multiplied or divided, the answer can contain no more significant figures than the least accurate measurement.

Multiplication & Division 9.2 cm x 6.8 cm x 0.3744 cm = 23.4225 cm3 = 23 cm3

Rounding When the answer to a calculation contains too many significant figures, it must be rounded off.

Rounding If the digit is smaller than 5, drop this digit and leave the remaining number unchanged. Thus, 1.684 becomes 1.68. If the digit is 5 or larger, drop this digit and add 1 to the preceding digit. Thus, 1.247 becomes 1.25.

Uncertainty in Measurements ______________ - measure of how close a measurement comes to the actual or true value of whatever is measured. ______________ - measure of how close a series of measurements are to one another. (depends on multiple measurements)

precise and accurate precise but not accurate