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Unformatted text preview: AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. The Scientific Method (Figure 1) Chemistry: study of matter and the I. Scientific Method: systematic approach to changes it undergoes. research. Called central science because basic A. Carefully define the problem (observation). knowledge of chemistry is essential for B. Perform experiments. studying other sciences (i.e. biology, physics, 1. Make careful observations. geology, and ecology) and subjects. 2. Record information/data about system, part of the universe that is under investigation. a. Qualitative: data consisting of general observations about the system. b. Quantitative: data comprising numbers obtained by various measurements of the system. c. Use standardized symbols and equations in recording measurements and observations to simplify process and to communicate w/others. C. Interpret or explain the observed phenomenon. 1. Hypothesis: tentative explanation for a set of observations. 2. Law: concise verbal or mathematical statement of a relationship between phenomena that is always the same under the same conditions. 3. Theory: unifying principle that explains a body of facts and/or those laws that are based on them. 4. Hypotheses, laws, and theories are constantly being discarded or modified so that they are consistent w/experimental observations. Figure 1 ~1~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. Classifications of Matter (Figure 2) I. Matter: anything that occupies space and has mass (including anything we see and touch, as well as things we cannot). A. Substance: form of matter that has a definite (uniform) composition and distinct properties (i.e. water, ammonia, table sugar, gold, and oxygen). B. Mixture: combination of two or more substances in which the substances retain their distinct identities (i.e. air, soft drinks, milk, and cement); do not have constant composition. 1. Homogeneous Mixture: composition of the mixture is same throughout (i.e. sugar dissolved in water). 2. Heterogeneous Mixture: composition of mixture is not uniform (i.e. sand mixed w/iron filings). 3. Any mixture can be created and then separated by physical means into pure components w/o changing the identities of the components (i.e. evaporate water to separate sugar and water; use magnet to separate iron filings from sand). C. Element: substance that cannot be separated into simpler substances by chemical means (i.e. hydrogen ± H, helium ± He, boron ± B, etc.). 1. Name them by using one or two letters. 2. 1st letter always capitalized; following letters are in lowercase. 3. Some elements¶ symbols are derived from their Latin names (i.e. aurum ± gold (Au); ferrum ± iron (Fe); natrium ± sodium (Na)). D. Compound: substance composed of atoms of two or more elements chemically united in fixed proportions; components are separated by chemical means (i.e. H2O). Separated by physical means. Separated by chemical means. Figure 2 ~2~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. The Three States of Matter (Figures 3,4) I. Solids: molecules are held close together in an orderly fashion w/little freedom of motion. II. Liquids: molecules are close together but are not held rigidly in position and can move past one another. III. Gases: molecules are separated by distances that are large compared w/size of the molecules. IV. The three states of matter can be interconverted w/o changing the composition of the substance (i.e. melting ± solid to liquid; boiling ± liquid to gas; freezing ± liquid to solid or gas to liquid). Figure 3 Figure 4 Physical and Chemical Properties of Matter I. Physical Property: property of substances that can be measured and observed without changing the composition or identity of a substance (i.e. melting point, boiling point, and color). II. Chemical Property: property of substances that is observed only after carrying out a chemical change (i.e. heating/burning). III. Extensive Property: depends on how much matter is being considered. A. Mass: quantity of matter in a given sample of a substance. B. Volume: length cubed; amount of space an object occupies. IV. Intensive Property: does not depend on how much matter is being considered. A. Density: mass of an object divided by its volume. B. Temperature ~3~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. Measurement I. Different instruments enable us to measure a substance¶s properties. A. Macroscopic Properties: properties that can be measured directly. 1. Meterstick measures length or scale. 2. Buret, pipet, graduated cylinder, and volumetric flask measure volume. 3. Balance measures mass. 4. Thermometer measures temperature. B. Microscopic Properties: properties that cannot be directly measured without the aid of a microscope or other special instrument (atomic or molecular scale). II. International System of Units (SI Units): modern metric system of measurement used by scientists internationally. A. SI Base Units B. Prefixes Used with SI Units III. Mass and Weight A. Mass: measure of the amount of matter in an object. 1. SI unit = kilogram (kg). 1 kg = 1000 g = 1 x 103 g 2. Gram (g) is more convenient to use. B. Weight: the force of gravity exerted on an object. C. The mass of an object remains constant but the weight may change depending on location (i.e. object on moon weighs only 1/6 what it does on Earth). ~4~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. IV. Volume (Figure 5) A. SI Unit = cubic meter (m3). B. Cubic centimeter (cm3) or cubic decimeter (dm3) is more convenient to use. C. Liter (L) and milliliter (mL) are common units of volume. 1 cm3 = 1 x 10±6 m3 1 dm3 = 1 x 10±3 m3 1L = 1000 mL = 100 cm3 = 1 dm3 1 mL = 1 cm3 Figure 5 V. Density: the amount of mass in a unit volume of a substance (expressed in kg/m3 or g/mL = g/cm3 or g/L). 1 g/cm3 = 1 g/mL = 1000 kg/m3     1 g/L = 0.001 g/mL Ex. A piece of gold ingot with a mass of 301 g has a volume of 15.6 cm3. Calculate the density of gold.  Ex.       The density of mercury, the only metal that is liquid at room temperature, is 13.6 g/mL. Calculate the mass of 5.50 mL of the liquid.         VI. Temperature (Figure 6) A. Fahrenheit (oF) Scale: most commonly used in U.S. outside the laboratory; 32oF = freezing point of H2O and 212oF = boiling point of H2 O. B. Celsius (oC) Scale: 0oC = freezing point of H2O and 100oC = boiling point of H2O. C. Kelvin: SI base unit of temperature; ³absolute´ temperature scale because 0 K is the lowest temperature that can be attained theoretically. ?oC = (oF ± 32oF) x ?oF = x (oC) + 32oF ~5~ ? K = (oC + 273.15oC)  AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. Figure 6 Ex. A certain solder has a melting point of 224oC. What is its melting point in degrees Fahrenheit? ?oF = Ex. x (224oC) + 32oF = 435oF Helium has the lowest boiling point of all the elements at ±452oF. Convert this temperature to degrees Celsius. ?oC = (±452oF ± 32oF) x Ex. = ±269oC Mercury, the only metal that exists as a liquid at room temperature, melts at ±38.9oC. Convert its melting point to kelvins. ? K = (±38.9oC + 273.15oC)  = 234.3 K ~6~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. Handling Numbers I. Scientific Notation A. Regardless of their magnitude, all numbers can be expresses in the form: where N is a number btw 1 and 10 and n, the exponent, is a positive or negative integer (whole number). 1. Express 568.762 in scientific notation: 5.68762 x 102 2. Express 0.00000772 in scientific notation: 7.72 x 10±6 B. Addition and Subtraction 1. Write each quantity, N1 and N2, with the same exponent n. 2. Combine N1 and N2; the exponent remains the same. Ex. (7.4 x 103) + (2.1 x 103) = 9.5 x 103 (2.22 x 10±2) ± (4.10 x 10±3) = (2.22 x 10±2) ± (0.41 x 10±2) = 1.81 x 10±2 C. Multiplication and Division 1. Multiply N1 and N2 in the usual way, but add the exponents together. 2. Divide N1 and N2 as usual and subtract the exponents. Ex. (8.0 x 104) x (5.0 x 102) = 40 x 106 = 4.0 x 107 = II. Significant Figures: meaningful digits in a measured or calculated quantity (when significant figures are used, it is understood that the last digit is uncertain; used to ensure precise data). A. Any digit that is not zero is significant (i.e. 1.234 4). B. Zeros between nonzero digits are significant (i.e. 40,501 5). C. Zeros to the left of the first nonzero digit are not significant (i.e. 0.0000349 3). D. If a number is greater than 1, then all the zeros written to the right of the decimal point count as significant figures (i.e. 3.040 4). E. If a number is less than 1, then only the zeros that are at the end of the number and the zeros that are between nonzero digits are significant (i.e. 0.003050 4). F. For numbers that do not contain decimal points, the trailing zeros may or may not be significant (hint ± change quantity to scientific notation) (i.e. 400 4.00 x 102 3 or 4.0 x 102 2 or 4 x 102 1). III. Significant Figures in Calculations A. Addition and Subtraction ± answer cannot have more digits to the right of the decimal point than either of the original numbers. Ex. 89.332 + 1.1 = 90.432 90.4 2.097 ± 0.12 = 1.977 1.98 B. Multiplication and Division ± number of significant figures in the final product or quotient is determined by the original number that has the smallest number of significant figures. Ex. 2.8 x 4.5039 = 12.61092 13 0.0611 ~7~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. C. Keep in mind that exact numbers obtained from definitions or by counting numbers of objects can be considered to have an infinite amount of significant figures. Ex. If an object has a mass of 0.2786 g, then the mass of eight such objects is 0.2786 g x 8 = 2.229 g. Ex. To take the average of two measured lengths 6.64 cm and 6.68 cm, we write   . D. In chain calculations, we will show the correct number of significant figures in each step of the calculation. IV. Accuracy and Precision (Figure 7) A. Accuracy: refers to how close a measurement is to the true value of the quantity that was measured. B. Precision: refers to how closely two or more measurements of the same quantity agree with one another. C. Highly accurate measurements are usually precise, but highly precise measurements do not necessarily guarantee accurate results. Figure 7 ~8~ AP Chemistry Chapter 1: Chemistry: The Study of Change Do not submit this as your own. Dimensional Analysis in Solving Problems I. Dimensional Analysis (Factor-Label Method): procedure that is used to convert between units in solving chemistry problems. Ex. We know that 1 dollar = 100 pennies. Therefore, two conversion factors can be created.    or  ? pennies = 2.46 dollars 2.46 dollars x   In general, to apply dimensional analysis we use the relationship: given quantity x conversion factor = desired quantity = 246 pennies In general, to cancel units: given unit x ~9~   = desired unit ...
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