BRCC CHM 101 Class Notes Chapter 1 Page 1 of 7 Chemistry - the study of matter, its behavior and interactions. matter - anything that takes up space and has mass mass - the substance which makes up the physical world; mass is made of atoms and is constant weight - a measure of mass that depends on gravity; weight changes depending on where you are measuring. modern science - based on systematic gathering of facts and careful observations - science is widely used to guide the development of technology scientific method - 4 step process: 1. make observations and collect data 2. propose a hypothesis 3. test the hypothesis 4. accept or reject the hypothesis - * If strongly supported by data, a hypothesis may become a theory. exponential notation - a way to handle very large or very small numbers - it is based on powers of 10 1,000 = 10 x 10 x 10 or 10 3 * The exponent indicates the number of times we multiply 10 by itself and how many zeros follow the one. 10 6 means that there are six zeros after the 1 or 1,000,000 * There are also negative powers of 10 in which you divide by the number of 10 s indicated. 1 1 10-4 = ------ = ------------ =.0001 10 4 10,000 * Numbers are often expressed as a coefficient with an exponent. 6.4 x 10 3 = 6.4 x 1,000 = 6,400 2.7 x 10-5 = 2.7 x.00001 =.000027 rules for writing in scientific notation: 1. When writing numbers in scientific notation, coefficients have only one digit to the left of the decimal. 2.5431 2. If you need to move the decimal to the left, then your exponent is a positive number indicating the number of times you must move the decimal to put it in scientific notation. 58,652 = 5.8652 x 10 4 3. If you need to move the decimal to the right, your exponent will be negative..00346 = 3.46 x 10-3
BRCC CHM 101 Class Notes Chapter 1 Page 2 of 7 rules for calculating with exponents: 1. Adding and Subtracting - adding and subtracting exponents are allowed only if the numbers have the same exponent. Add or subtract the coefficient and leave the exponent alone. 2.5 x 10-3 + 3.0 x 10-3 -------------------- 5.5 x 10-3 2. Multiplication - multiplying is a 2 step process: (1) multiply the coefficients (2) add the exponents 7.40 x 10 5 x 3.12 x 10 9 ----------------------- 23.1 x 10 14 -------------------> 2.31 x 10 15 3. Division - dividing is a 2 step process: (1) divide the coefficients (2) subtract the exponents 6.4 x 10 8 6.4 10 8 ------------------ first -------- = 2.5 then ------- = 10-2 so that it is 2.5 x 10-2 2.57 x 10 10 2.57 10 10 measurement - there are always 2 parts to a measurement: a number and a unit *always give the units. 68 lbs is different from 68 oz. * science uses SI units (International System of Units) which are meter, kilogram, Kelvin * chemistry units of measurement: meter, liter, gram, second, Kelvin or Celsius degree prefixes are used to convert to smaller or larger units Prefix Symbol Value giga G 10 9 = 1,000,000,000 mega M 10 6 = 1,000,000 kilo K 10 3 = 1,000 hecto h 10 2 = 100 deca da 10 deci d 10-1 = 0.1 centi c 10-2 = 0.01 milli m 10-3 = 0.001 micro µ 10-6 = 0.000001 nano n 10-9 = 0.000000001 * memorize these prefixes
BRCC CHM 101 Class Notes Chapter 1 Page 3 of 7 length - basic unit is the meter, which is about 39 inches - a little longer than a yard 1 kilometer (km) = 1,000 meters (m) 1 centimeter (cm) = 0.01 meter volume - the space occupied by something - the basic unit is the liter (L) - a little bigger than a quart 1,000 milliliter (ml) = 1 liter (L) * the ml is common in chemistry 1 cubic centimeter (cc) = 1 ml * an important relationship to remember mass - the quantity of matter in an object - basic unit is the gram (g) - there are about 454 g in a lb 1 kilogram (kg) = 1,000 g 1,000 milligrams (mg) = 1 g * things to remember: (1) We measure mass with a balance. (2) Mass and weight are different - mass is independent of where you are and weight depends on gravity. (3) We can use them interchangeably on earth. time - the basic unit is the second (s) - 60 s = 1 min & 60 min = 1 hr temperature - the Celsius or centigrade scale is the common standard - Kelvin is the SI standard method to convert between Fahrenheit and Celsius Fahrenheit Celsius boiling point of H2O -- -- 212 F -- -- 100 C 180 degrees -------> <------ 100 degrees freezing pt of H 2 O -- -- 32 F -- -- 0 C -- -- 0 F * For Fahrenheit, between the freezing point and boiling point of water there are 180 degrees. * For Celsius, between the freezing point and boiling point of water there are 100 degrees. 100 5 180 9 ------ = ----- and ------ = ----- = 1.8 180 9 100 5 * Which degrees are bigger? Celsius degree is larger because there are more (smaller) Fahrenheit degrees.
BRCC CHM 101 Class Notes Chapter 1 Page 4 of 7 * To convert from F to C first subtract 32 degrees and then multiply by 5/9. 5 C = ( F - 32 F) x ---- 9 * To convert from C to F first multiply by 9/5 (or 1.8) and then add 32 degrees. 9 F = ( C x ---- ) + 32 or ( C x 1.8) + 32 5 Kelvin (K) scale is absolute - this means 0 K is absolute zero! Do not use the degree symbol with Kelvin degrees. K = C + 273.15 Temperature Comparisons Celsius Temperature ( C) Fahrenheit Temperature ( F) Description 0 32 Freezing Point of water 21 70 Room Temperature 25 77 Standard Temperature 37 98.6 Body Temperature 64 147 Too hot to hold > 4 sec.s 100 212 Boiling Point of water unit conversions dimensional analysis - (also called factor-label method) is a method of working through complex problems using units and conversions. * When multiplying numbers we also multiply units and when dividing numbers we also divide units * conversion factor - a ratio of 2 different units convert 381g to lbs you know there are 453.6 g in 1 lb 453.6 g 1 lb so there are 2 possible conversion factors : --------------- or -------------- 1 lb 453.6 g 381 g 1 lb x ------------- = 0.840 lb 453.6 g
BRCC CHM 101 Class Notes Chapter 1 Page 5 of 7 * When using a conversion factor, put the units you want to end up with on top and cancel out the units you want to get rid of. convert 132 lbs to kilograms 1 Kg = 1,000 g 132 lbs 453.6 g 1 kg x ----------- x ------------- = 59.9 Kg 1 lb 1,000 g Conversion Table Physical Quantity Conversion Factor Length inches cm 1 inch = 2.54 cm Volume liters quarts 1 L = 1.057 qts. Mass pounds grams 1 lb. = 453.6 g The States of Matter Matter has 3 states: solid, liquid, and gas Solid - solids have a definite shape and volume - they vary in their hardness and brittleness from substance to substance. Solids are not compressible. Liquid - liquids have a definite volume and are not compressible. Liquids do not have definite shapes; they will take the shape of the bottom of their containers and will spread out on a flat surface. Gas - gases do not have either a definite volume or a definite shape; they take both the volume and the shape of their container and are easily compressible. Three types of processes will concern us in chemistry: physical change - substances change their form or phase but not their essential nature. melting, boiling, dissolving, and grinding into a powder. chemical change - chemical reaction - one set of substances (reactants) is transformed into another set of substances (products). combustion. nuclear reaction - deals with radioactivity. nuclear decay. Density mass of a substance divided by its volume d = m / V units are g/ml or g/l (gases) density is a characteristic property of a substance - a physical property which is constant at constant temperature and can be used to help identify a substance. density of a solid or liquid changes with temperature ===> as Temp the density If 73.2 ml of a liquid has a mass of 61.5 g, what is the density? mass 61.5 g d = ---------- = -------------- = 0.840 g/ml volume 73.2 ml
BRCC CHM 101 Class Notes Chapter 1 Page 6 of 7 If the density of a piece of metal is 7.86 g/ml, then what is the volume of a piece of that metal weighing 524 g? 524 g 1 ml x --------- = 66.7 ml 7.86 g Specific gravity - is the density of a substance divided by the density of water (which is usually 1.00 g/ml) specific gravity has no units. The density of copper (Cu) at 20 C is 8.92 g/ml. The density of water at 20 C is 1.00 g/ml. What is the specific gravity of Cu? 8.92 g/ml --------------- = 8.92 which means that copper is 8.92 times as dense as water 1.00 g/ml extensive properties - properties of a substance which depend on the quantity of material. mass and volume - these are not useful in identifying a substance. intensive properties - properties of a substance which are independent of sample size. density, solubility, boiling point - these are useful in identifying a substance energy - the capacity to do work - 2 types: kinetic and potential kinetic energy - energy of motion - increases as an object moves faster potential energy - stored energy chemical energy - a form of potential energy released when chemicals react - piece of paper has chemical energy released when it is burned (chemical reaction) principle of nature - objects tend to seek their lowest possible potential energy - this is why water flows down hill Law of Conservation of Energy - energy can neither be created nor destroyed - it is converted from one form to another. heat - a type of energy - not the same as temperature - heat is measured in calories calorie, cal, - the amount of heat necessary to raise the temperature of 1 g of H 2 O by 1 C kilocalorie, kcal = 1,000 cal * nutritionists use the Calorie to mean the same thing as the kcal heat is also measured in Joules (J) 1 cal = 4.184 J
BRCC CHM 101 Class Notes Chapter 1 Page 7 of 7 Specific Heat - the amount of heat (calories) needed to raise the temperature of 1 g of any substance by 1 C - each substance has its own specific heat How is specific heat used? Heat absorbed = Specific Heat x mass x (T 2 - T 1 ) where T 1 = initial temperature & T 2 = final temperature How many calories are required to heat 352 g of water from 23 C to 95 C? heat = 1.00 cal/g deg x 352 g x (95 C - 23 C) = 2.5 x 10 4 cal hypothermia - hyperthermia - condition where body temperature drops - 1 or 2 C causes shivering - if it drops more than this, then unconsciousness and death will result. body temperature rises - caused by high outside temperature or fever - a sustained temperature of 41.7 C (107 F) or more is fatal