CHAPTER 1 AP CHEMISTRY

TYPES OF MATTER ► PURE SUBSTANCE  the same throughout ► ELEMENTS  Fixed properties, substance cannot be broken down chemically ► COMPOUNDS  Two or more elements chemically bonded, fixed properties, can be broken down chemically

PHYSICAL PROPERTIES/CHANGES ► Properties  Can be measured and will usually be the same  Color, density, boiling point, melting point, hardness ► Change  Properties remain the same throughout a physical change ► Phase change  Solid, liquid, gas ► Mass or volume change

CHEMICAL PROPERTIES/CHANGES ► Properties  The way a substance reacts with another substance  2Na(s) + Cl 2 (g) --> 2NaCl(s)  Sodium and water react violently and release energy ► Changes  Identity of the substance is altered  Sodium metal and chlorine gas are deadly to humans, but sodium chloride is needed for humans to survive

MIXTURES ► HOMOGENEOUS  Uniformly mixed, all in the same phase  Air, salt water ► HETEROGENEOUS  Not uniformly mixed, different phases  Sand, wood, blood ► CAN BE SEPERATED BY PHYSICAL MEANS  Filtration, chromatography, distillation (this occurs due to the volatility of the substances)

MEASUREMENTS PAGE 8 ► LENGTH ► BASIC UNIT - METER  1m = 10 2 cm = km  1nm = mm = m  Common unit prefixes - kilo, centi, milli, nano ► MASS ► BASIC UNIT KILOGRAM  COMMON PREFIXES  Kilo, milli, mega

TEMPERATURE ► UNIT  CELSIUS - o C  FAHRENHEIT - O F  KELVIN - K ► Temperature is the factor that determines the direction of heat flow ► Temperature is measured indirectly by measuring its effect upon the properties of a substance ► Temperature depends on a linear expansion

RELATIONSHIP BETWEEN CELSIUS AND FAHRENHEIT ► Celsius and Fahrenheit when compared to each other form a linear line  y = mx + b B = y when x is 0  m = y 2 - y 1 T f = T c (9 o F/5 o C) + 32 x 2 - x 1 x 2 - x 1 ► Boiling and melting points ► = 9/5 = ► O F = 1.8 O C + 32

CELSIUS AND KELVIN ► Kelvin is known as the absolute scale, used in chemistry  0K = o C  T K = T C ► During the lunar month, when the surface of the moon is facing the sun, the temperature will reach a high of 251 o F. Express this in o C and K. ► During the dark period of the moon, the temperature drops to -137 o C. Express this in o F and K. ► Express the body temperature, 98.6 o F in o C and K

ENERGY ► SI unit is Joule  1J = 1 N. m = 1 kg. m 2 /s 2 ► Relationship between calories and Joules  1cal = J ► PROPERTIES  INTENSIVE  The value is not dependent on the amount of material you have  Density or temperature ► EXTENSIVE  Depends on the amount  Heat content, mass, volume

UNCERTAINITY IN MEASUREMENTS ► Every measurement has a degree of uncertainty. Human error or balances that are calibrated differently. ► With each measurement the uncertainty should be noted (measure a book to nearest dm) ► ACCURATE  How close the measurements are to the “true” value ► PRECISION  How close an individual measurement is to other measurements  Look at drawings on overhead

DERIVED UNITS ► VOLUME  SI unit is m 3  1cm 3 = (10 -2 m) 3 = m 3  1L = 1000 mL =1000 cm 3 ► FORCE  SI unit is Newton  1N = 1kg. 1m/s 2 ► PRESSURE  SI unit is Pascal  1Pa = 1N/m 2  Standard atmosphere is x 10 5 Pa

SIGNIFICANT FIGURES ► State of degree of confidence in the measurement cited ► Nonzero integers:  Nonzero integers are always significant ► Zero’s. There are three classes or zero’s  Leading zero’s precede (before) all nonzero digits. ARE NOT SIGNIFICANT  Captive zero’s are between two nonzero digits. ARE SIGNIFICANT  Trailing zero’s are to the right of nonzero integers. ONLY SIGNIFICANT IF A DECIMAL POINT IS PRESENT and ► Three students weigh an object on different balances. How many significant figures. are there in each value  A g  B g  C kg

ROUNDING NUMBERS ► In a series of calculations carry all digits unit the final solution, THEN ROUND ► If a digit needs to be rounded  If it is less than 5, the preceding digit remains the same   ► If the digits are equals or is greater than 5, the preceding digit is increased by one.   506  ► A person’s height is measured to be inches. What is the height in centimeters? (Hint 1 inch = 2.54 cm)

UNCERTAINITY IN NUMBERS ► Multiplication and division  Significant figures are the same as the least precise (number with the smallest number of significant figures) measurements ► Addition and subtraction  The answer will have the same number of digits beyond the decimal point as the integer (that was added or subtracted) with the least accurate number (last significant number is in the highest place holder) ► Three students each weigh a object  Student g  Student  Student  How many significant figures should be reported for the total weight?

EXACT NUMBERS ► What is an exact number ► Infinite like pi, 1m = 100 cm ► 1 cal = J gives two conversion factors ► 1cal J ► J 1 cal ► A piece of iron with a volume of 2.50 gal. weighs lbs. Calculate the density of iron in scruple/drachm. Some conversion factors are: ► 1.00 L = gal mL = drachm ► kg = lb 1000 g = 1 kg ► scruple = g 1000 mL = 1 L ► A certain printed page has an average of 25 words per square inch of paper. The average length of the words is 5.3 letters. What is the average number of letters per square centimeter of paper? (Hint 1 inch = 2.54 cm)

DENSITY, MELTING AND BOILING POINTS ► DENSITY  Mass/volume, unit = g/cm 3  A student pipets cm 3 of isopropyl alcohol (rubbing alcohol) into an empty flask weighing g. She finds that the mass of the flask and isopropyl alcohol is g. Calculate the density of isopropyl alcohol to the correct number of significant figures. ► Melting point  Temperature at which solid goes to liquid phase, it is an intensive property, molecules have more energy ► Boiling point  Temperature at which liquid goes to gas ► Solubility  Different compounds have different solubility's at different temperatures ► Usually solubility of a solid goes down as the temperature goes down (except KOH)