CHAPTER 1 CE CHEMISTRY

SCIENTIFIC METHODS The steps in a scientific method are repeated until a hypothesis is supported or discarded.

MATTER Matter is anything that has mass and takes up space Weight Mass The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction, it is conserved. Movie clip The mass of the reactants equals the mass of the products. massreactants = massproducts

States of Matter The physical forms of matter, either solid, liquid, or gas, are called the states of matter. http://lab.concord.org/embeddable.html#interactives/sam/phase-change/4-solids.json Solids are a form of matter that have their own definite shape and volume. Liquids are a form of matter that have a definite volume but take the shape of the container. http://lab.concord.org/embeddable.html#interactives/sam/phase-change/3-liquids.json

Properties of Matter Gas have no definite shape or volume. They expand to fill their container. Vapor refers to the gaseous state of a substance that is a solid or liquid at room temperature.

PROPERTIES OF MATTER THE PROPERTIES OF MATTER CANNOT BE BROKEN DOWN WITHOUT A CHEMICAL CHANGE It is a characteristic that can be observed or measured without changing the sample’s composition. Extensive properties, such as mass, length, and volume, are dependent on the amount of substance present. Intensive properties, such as density, are dependent on the what the substance is not how much there is.

PHYSICAL PROPERTIES is a characteristic that can be observed or measured without changing the sample’s composition.

PHYSICAL CHANGE A change that alters a substance without changing its composition Mercury ice transition of matter from one state to another. Boiling, freezing, melting, and condensing all describe phase changes in chemistry

CHEMICAL PROPERTIES The ability of a substance to combine with or change into one or more other substances Iron forming rust Copper turning green in the air 2Na(s) + Cl2(g)  2NaCl(s) Sodium is a very reactive metal that reacts with water Chlorine gas is a very reactive nonmetal that will form hydrochloric acid if breathed in

CHEMICAL CHANGE A change that involves one or more substances turning into new substances Decomposing, rusting, exploding, burning, or oxidizing are all terms that describe chemical changes When sodium metal reacts with chlorine gas you produce sodium chloride salt The physical and chemical properties change Sodium chloride is needed for a human to survive. Burning a piece of paper Magnesium burn

SUBSTANCES PURE SUBSTANCE ELEMENT COMPOUND pure substance that cannot be separated into simpler substances by physical or chemical means. 92 elements occur naturally on Earth COMPOUND made up of two or more elements combined chemically Most of the matter in the universe exists as compounds Unlike elements, compounds can be broken into smaller components by chemical means

MIXTURES MIXTURE a combination of two or more pure substances in which each pure substance retains its individual chemical properties HOMOGENEOUS – a mixture where the composition is constant throughout Also known as a solution Salt water or air HETEROGENEOUS – a mixture where the individual substances remain distinct Sand or wood

Separating Mixtures Filtration is a technique that uses a porous barrier to separate a solid from a liquid in a heterogeneous mixture. Distillation is a separation technique for homogeneous mixtures that is based on the differences in boiling points of substances. Crystallization is a separation technique for homogenous mixtures that results in the formation of pure solid particles from a solution containing the dissolved substance. Sublimation is the process of a solid changing directly to a gas, which can be used to separate mixtures of solids when one sublimates and the other does not Chromatography is a technique that separates the components of a mixture on the basis of tendency of each to travel across the surface of another material

ATOMS AND MOLECULES MOLECULES Diatomic molecule has two same atoms (know these), Hydrogen gas(H2), Nitrogen gas(N2), Oxygen gas(O2), Fluorine gas(F2), Chlorine gas(Cl2), Bromine liquid(Br2), Iodine solid(I2) Polyatomic molecules ATOMS All elements are single atoms Carbon (C), Aluminum (Al), except for the diatomic molecules

MATTER heterogeneous mixtures homogeneous mixtures(solutions) physical methods physical methods pure substances elements compounds chemical methods atoms nucleus protons neutrons electrons

METRIC PREFIXES Giga G 109 There are 109 units (puppies) in Mega M 106 1 gigapuppy Kilo k 103 Hecto h 102 Deca da 101 Unit (anything can be a unit) Common chemistry units gram, liter, meter, second, watt Deci d 10-1 There are 101decigrams in 1 gram Centi c 10-2 Milli m 10-3 Micro u 10-6 Nano n 10-9

SI UNITS moles Length is measured in meters Mass is measured in kilograms Time is measured in seconds Temperature is measured in Kelvin Amount of substance is measured in moles

CONVERSIONS THINGS TO REMEMBER In the metric system, the smaller prefix unit will always have a larger number than the prefix unit it is equal to. 1000 m = 1km (overhead) METER IS A SMALLER PREFIX UNIT Kelvin is absolute zero or -273.15 oC. You can not have a temperature lower than this so KELVIN CAN NEVER BE A NEGATIVE NUMBER oC + 273 = K K - 273 = oC

Units and Measurements SECTION2.1 Units and Measurements Zero kelvin is the point where there is virtually no particle motion or kinetic energy, also known as absolute zero. Two other temperature scales are Celsius and Fahrenheit. F = 1.8 C + 32

TEMPERATURE Celsius (oC) Freezing of water 0 oC Boiling of water 100 oC Convert the following temperatures 323 K to oC -20 oC to K 129 K to oF

Representing Data Graphing On line graphs, independent variables are plotted on the x-axis and dependent variables are plotted on the y-axis.

Significant Figures Often, precision is limited by the tools available Significant figures include all known digits plus one estimated digit

SIGNIFICANT FIGURES State of degree of confidence in the measurement cited Pacific and Atlantic rule If there is a decimal point present, start from the left, go to the first nonzero number. Start counting the numbers 0.0025 1.109 57000. If there is no decimal point, start from the right, go to the first nonzero number. Start counting the number 57000 100600 Three students weigh an object on different balances. How many significant figures are there in each value? A. 30.0 g B. 29.980 g C. 0.03 kg

ROUNDING NUMBERS OFF 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 4.499 5.234 If the digits are equals or is greater than 5, the preceding digit is increased by one. 4.8501 506 5.236 A person’s height is measured to be 57.50 inches. What is the height in centimeters? (Hint 1 inch = 2.54 cm)

UNCERTAINTIES IN MULTIPLICATION, DIVISION, ADDITION, AND SUBTRACTION Multiplication and division Least number of significant figures Addition and subtraction Least accurate number Three students each weigh a object Student 1 129.0 g Student 2 53.21 g Student 3 1.4365 g How many sig. figs. Should be reported for the total weight?

EXACT NUMBERS What is an exact number? 1 cal = 4.184 J gives two conversion factors 1cal 4.184 J 4.184 J 1 cal A piece of iron with a volume of 2.50 gal weighs 168.04 lbs. Calculate the density of iron in scruple/drachm. Some conversion factors are: 1.00 L = 0.264 gal 1.000 mL = 0.2816 drachm 1.000 kg = 2.205 lb 1000 g = 1 kg 1.000 scruple = 1.296 g 1000 mL = 1 L

SCIENTIFIC NOTATION All chemistry uses scientific notation Uses the base 10 1000 = 10 x 10x 10 =103 0.001=1/1000=1/10 x 1/10 x 1/10=10-3 23000 = 2.3 x 104 1010. = 1.010 x 103 0.00120 = 1.20 x 10-3

PERCENTAGES Calculating percentages Percent =number of specific items x 100 Total items in the group A count of 62300 white blood cells was found in a patient, if the normal white blood count is 78000. What percent of white blood cells does this patient have?

DENSITY Density is a derived unit, g/cm3, the amount of mass per unit volume. The density equation is density = mass/volume A merchant sold you a chain that was suppose to be pure gold. You took it home, when you weighed it was 23.5 g. You then filled up a graduated cylinder to 15.56 mL, when you put the chain in the water it went up to 16.83 mL. Is this pure gold? (Hint gold’s density is 19.2 g/mL)