INTRODUCTION

CHEMISTRY Is the study of the composition of materials and the changes that these materials undergo Wood burns Plants grow Iron rusts Bread bakes Human digestion

Branches of Chemistry Analytical chemistry Physical chemistry Answers questions about composition (what is the level of lead in that drinking water?) Physical chemistry Deals with energy transfers in chemical processes (how much energy is stored in a battery?) Biochemistry Deals with the analysis of chemical processes in living things (cellular process such as photosynthesis and respiration) Organic chemistry Study of carbon containing molecules (overlap with biochem) Inorganic chemistry Study of the chemistry of nonliving things (geological chemistry, the analysis of the rate of corrosion of metals)

The Scientific Method State the problem Make observations Form a hypothesis Perform an experiment Variable you change – called the “independent” or “manipulated” variable Variable you observe – called the “dependent” or “responding” variable Develop a theory (a well-tested explanation for observations) Continue to experiment Modify theory as needed Develop a scientific law (a summary of many observations and experiments)

Chapter 2: Matter & Change Matter – anything that has mass and volume _____________________ – require measurements Mass – amount of matter, measured in grams (g) Volume – amount of space an object occupies, measured in: liters (L) milliliters (ml) cubic centimeters (cm3) _________________ – descriptions, not measured Color, texture, odor, opaque, clear, dense, sound, taste (don’t taste anything in the lab!)

Classification of matter

Matter: Substances and Mixtures Substances – pure composition Two types: __________ – only one kind of atom, such as iron (the symbol is on the periodic chart) __________ – a combination of atoms, such as iron oxide (which can be separated) Mixtures – contains 2 or more substances ______________ – the same throughout; dissolved (saltwater) ______________ – the sample may different depending where you take it in the container (orange juice with pulp)

States of Matter Solid- rigid shape, incompressible, fixed volume, usually particles tightly packed and organized) Liquid- indefinite shape but fixed volume, incompressible, flows, usually less tightly packed than solid (by a few %), less organized Gas- indefinite shape and volume, flows, particles far away from each other, disorganized, compressible

CHEMICAL REACTIONS Chemical Reaction Reactant Product A change in which ________________________________________________________________________ Reactant A ___________________________________ Product

Physical Properties and Changes Physical Property – characteristics that describe a substance Can be observed without changing the substances composition. Physical Change – a change that does not affect the composition of the substance The change may be reversible (melting) or irreversible (tearing)

Recognizing Chemical Changes You know a chemical change has occurred if: you see a change in color there is a change in temperature (hot or cold) a gas is produced a solid precipitate is formed an odor is produced

Separation of a Mixture Difference in physical properties can be used to separate mixtures. Filtration- separates solid from a liquid (passes through a filter (pores)) Distillation-liquid is boiled to produce a vapor that is then condensed into a liquid

Law of Conservation of Mass During any physical or chemical change, the mass of the products is always equal to the mass of the reactants. MASS is NEITHER CREATED or DESTROYED Example: making pizza Physical Change: the mass of the dough + sauce + cheese separately = the mass of all three together Chemical Change: the mass of the ingredients before it’s cooked = the mass after it’s cooked (as long as it didn’t burn!)

DENSITY Mass Volume Density Amount of matter in an object Volume Amount of space an object occupies Density Mass per unit volume Percent Error = /theoretical-experimental/ x 100% theoretical

Density Practice A copper penny has mass of 3.1g and volume of 0.35cm3. What is the density of copper?

Measurements Three types of measurement Length: meter (m) Mass: gram (g) Volume: Liter (L)

Measurements expressed in SCIENTIFIC NOTATION The expression of numbers in terms of M x 10n M ≥ 1.00 and M < 10 n is an integer Convert to whole numbers 1 x 103 = _______ 1 x 102 = _______ 1 x 101 = _______ 1 x 100 = _______ 1 x 10-1 = _______ 1 x 10-2 = _______ 1 x 10-3 = _______

TRY THESE 25,000 ______________ 0.00468 0.0100

Metric Conversions Kilo . Hecto . Deka . (unit) . Deci . Centi . Milli … Micro … Nano m g L Write the following in regular notation and scientific notation How many mm in a m? _____________ How many cm in a m? _____________ How many m in a km? _____________

Measurements

ACCURACY/PRECISION Accuracy Precision How close a measurement is to the actual value Precision How close a set of measurements are to each other

Temperature Official” unit = Kelvin (K) Most widely used for measurement = degrees Celsius (ºC) Temp in Kelvin = ºC + 273 (º C = K -273) Examples: ice water = 0 ºC = 273 K Boiling water = 100 ºC = 373 K Body temp = 37 ºC = 310 K (about 99 ºF)

SIGNIFICANT DIGITS or Figures This is a process used to determine the number of digits to round to when measuring an object. Use this process when Measuring mass (on the scale) – g, kg, etc. Measuring volume (in a graduated cylinder) – ml L, etc. Measuring length (with a ruler) – cm, m Is used to communicate to other scientists how accurate your measurement is: Does your scale measure to the hundredths place, tenths place or whole number? Referred to as “Sig Figs”

How to determine the number of Sig Figs in a measured value Atlantic-Pacific Method A = decimal Absent, begin counting from right P = decimal Present, begin counting from left Try these: 1,000 1 sig fig 0.001 0.0010 2 sig fig 1000.0 5 sig fig

Rules for Using Sig Figs Multiplication/Division Do all calculations, then round to the same number of digits as the number with the smallest number of sig figs 4.56 x 1.4 = 6.384 Round to 2 sig figs: 6.4 8.315/298 = 0.0279027 Round to 3 sig figs: 0.0279 Addition/Subtraction Do the calculations, then round to the place of the number with the smallest number of decimal places 12.11 + 18.0 + 1.013 = 31.123 Round to 31.1 88.88 – 2.2 = 86.68 Round to 86.7 (note: if the number after 6 is > 5, round up)

Rules for Using Sig Figs Multiple step calculations Use an overbar to keep track of the significant figures from step to step. Round only when reporting the final answer Example: 88.88 – 86.66 2.22 .024977 (calculator 88.88 88.88 answer) Based on 2.22, round to 3 sig figs .024977 If the number after the place you want to round to is > 5, round up (in this case 7). Ignor the other 7. Answer = .0250 The zero after the 5 is significant. You must show it! = =