Chemistry 1411 Joanna Sabey Chapter 1: Chemistry: The Study of Change

Chemistry Chemistry: The study of matter and the changes it undergoes. Types of Chemistry: Inorganic Chemistry Organic Chemistry Biochemistry Analytical Chemistry Physical Chemistry

The Study of Chemistry Macroscopic World: the things we can see, touch, and measure directly. Microscopic World: the things we cannot experience without modern technology and our imaginations.

The Scientific Method Scientific method: a systematic approach to research. Step One: Observation, carefully define the problem. Step Two: Performing experiments, recording information, gathering data, two types: Qualitative data: general observations about the system. Quantitative data: comprising numbers obtained by various measurements of the system. Step Three: Formation of a hypothesis: a tentative explanation for a set of observations. Step Four: Formation of Law: a concise verbal or mathematical statement of a relationship between phenomena that is always the same under the same conditions. Step Five: Formation of Theory: a unifying principle that explains a body of facts and/or those laws that are based on them.

Classification of Matter Matter: Anything that occupies space and has mass. Substance: a form of matter that has a definite composition and distinct properties. liquid nitrogen gold ingots silicon crystals

Mixtures Mixture: A combination of two or more substances in which the substances retain their distinct identities. Homogeneous mixture: the composition of the mixture is the same throughout, salt dissolved in water. Heterogeneous mixture: the composition of the mixture is not uniform, sand mixed with iron fillings. Physical means can separate both mixture types.

Elements and Compounds Element: a substance that cannot be separated into simpler substances by chemical means. 114 elements have been identified 82 elements occur naturally on Earth gold, aluminum, lead, oxygen, carbon, sulfur 32 elements have been created by scientists

Elements and Compounds

Compound: A substance composed of atoms of two or more elements chemically united in fixed proportions, can be separated by chemical means into their pure substances. lithium fluoride dry ice – carbon dioxide

Classification of Matter

The Three States of Matter

Physical and Chemical Properties Physical Property: Property that can be measured or observed without changing the composition or identity of a substance. ex: melting point and boiling point. Physical Change: A change that does not alter the composition or identity of a substance. Ex: melting of ice, dissolving of sugar in water. Chemical Property: Property that changes the substance chemically. Ex: Hydrogen gas burning in air, oxygen gas, to form water. Chemical Change: A change that alters the composition or identity of the substance involved. Ex: burning and rusting.

Extensive and Intensive Properties Extensive Properties: Depend on how much matter of the substance is being considered. Mass: the quantity of matter in a given sample Length Volume Intensive Properties: Do not depend on how much matter of the substance is present. Density: the mass of an object divided by its volume. Temperature Color

Mass and Weight Mass: the measure of the amount of matter in an object, SI unit is kilograms, kg. Weight: the force that gravity exerts on an object.

Scientific Notation Scientific notation: utilizes the significant digits in a measurement followed by a power of 10. The significant digits are expressed as a number between 1 and 10. If n>0, the decimal moves to the left  X 10 2 If n<0, the decimal moves to the right  7.72 X 10 -6

Unit Conversions SI units can be converted using the prefix meanings: PrefixSymbolMultiple/FractionExample tera-T1,000,000,000,000 = 1 X Tm=1 X m giga-G1,000,000,000 = 1 X Gm=1 X 10 9 m mega-M1,000,000 = 1 X Mm = 1 X 10 6 m kilo-K1000 = 1 X Km = 1 X 10 3 m Basic unit--- deci-d0.1 = 1 X dm = 1 X m centi-c0.01 = 1 x cm = 1 x m milli-m0.001 = 1x mm = 1x m micro-µ = 1 x µm = 1 x m nano-n = 1x nm = 1x m pico-p = 1x pm = 1x m

Unit Conversions How many days are in 2.5 years? Step 1: What are you converting to? We want days. Step 2: What are you given? 2.5 years. Step 3: What is the conversion factor? 1 year = 365 days, set up the conversion so the units cancel that you no longer want.

Metric Unit Conversions The mass of the earth is 5.98 X kg. What is the mass expressed in Megagrams (Mg) ? Step 1: What are you converting to? We want Mg Step 2: What are you starting with? We are given 5.98 X kg Step 3: What are the conversion factors you are using? Conversion 1: 1kg = 1000g Conversion 2: 1 X 10 6 g = 1 Mg 5.98 X kg X (1000 g / 1kg) X (1 Mg / 1 X 10 6 g) = 5.98 X Mg

Metric-English Unit Conversions A can of soda contains 12.0 fl.oz. (1 quart = 32 fluid ounces). What is the volume of soda in mililiters? Step 1: we are looking for mL Step 2: 12.0 fl.oz. Step 3: 1qt. = 32 fl.oz. and 1 qt. = 946 mL 12.0 fl.oz. X (1 qt./ 32 fl.oz.) X (946 mL / 1 qt. ) = 355 mL Physical QuantityEnglish unitMetric Equivalent Length1 inch (in.)1 in. = 2.54 cm Mass1 pound (lb.)1 lb = 454 g Volume1 quart (qt)1 qt = 946 mL Time1 second (sec)1 sec = 1.00 s

Unit Conversions with Volume Volume: SI derived unit for volume is cubic meter(m 3 ). To convert cubic units, the conversion factor must be cubed. 1 mL = 1cm 3 1 cm 3 to m 3 1 cm 3 X (1 m / 100 cm) 3 = 1 X m 3 1 dm 3 to m 3 1 dm 3 X (1 m / 10 dm) 3 = 1 X m 3

Density SI units for density are 1g/mL = 1g/cm 3 = 1 kg/m 3 D= m/V A piece of gold ingot with a mass of 301 g has a volume of 15.6 cm 3. Calculate the density of gold. D= 301 g / 15.6 cm 3 = 19.3g/cm 3

Density The density of mercury, the only metal that is a liquid at room temperature, is 13.6 g/mL. Calculate the mass of 5.50 mL of the liquid. M = D X V M= 13.6 g/mL X 5.50 mL = 75 g

Temperature Scale 0 F = x 0 C C = ( 0 F – 32) X K = 0 C

Temperature Scale Solder is an alloy made of tin and lead that is used in electronic circuits. A certain solder has a melting point of 224°C. What is its melting point in degrees Fahrenheit? 0 F = ( 9/5) x C F = 435 Helium has the lowest boiling point of all the elements at -452°F. Convert this temperature to degrees Celsius. 0 C = (-452 – 32) X (5/9) 0 C = -269 Mercury, the only metal that exists as a liquid at room temperature, melts at 238.9°C. Convert its melting point to Kelvin. K= C K= 512

Scientific Notation Addition or Subtraction: Write each quantity with the same exponent n Combine N 1 and N 2 The exponent, n, remains the same 4.31 x x 10 3 = 4.31 x x 10 4 = 4.70 x 10 4 Multiplication: Multiply N 1 and N 2 Add exponents n 1 and n 2 (4.0 x ) x (7.0 x 10 3 ) = (4.0 x 7.0) x ( ) = 28 x = 2.8 x Division: Divide N 1 and N 2 Subtract exponents n 1 and n x 10 4 ÷ 5.0 x 10 9 = (8.5 ÷ 5.0) x = 1.7 x 10 -5

Significant Figures Any digit that is not zero is significant kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant g 3 significant figures

Significant Figures Determine the number of significant figures in the following measurements: 478 cm 3 sig. figs 6.01 g 3 sig. figs m 3 sig. figs kg 2 sig. figs × atoms 4 sig. figs.

Significant Figures Addition or Subtraction: The answer cannot have more digits to the right of the decimal point than any of the original numbers = , the answer must be rounded because the most accurate answer is that with one significant figure behind the decimal – = , the answer must be rounded because the most accurate answer is the one with two significant figures behind the decimal, 0.79

Significant Figures Multiplication and Division: The number of significant figures in the final answer is set by the original value that has the total smallest number of significant figures x = the final answer must be rounded because the most accurate answer is the one with 3 significant figures total, ÷ = the final answer must be rounded because the most accurate answer is the one with 2 significant figures total, 0.061

Accuracy and Precision Accuracy: how close a measurement is to the true value Precision: how close a set of measurements are to each other