Introduction to Chemistry

Transcription

1 Introduction to Chemistry CHEMISTRY = the study of the composition of matter, its chemical and physical changes, and the changes that accompany these changes. Scientific law vs. theory: Scientific law- Scientific theory- THE WAY SCIENCE WORKS Science involves critical thinking, or applying logic and reason to observations and conclusions. Observation vs. Inference: Observation- Inference- Variables and Controls: A variable is anything that can in an experiment. Independent variable: The variable being or by the scientist. Dependent variable: The variable being or by the scientist. A tests only one variable at a time. The Scientific Method: A series of logical steps to follow in order to solve problems. FORMULATE A FORM A DESIGN AND CONDUCT AN MAKE AND DATA DRAW FORMULATE and Making Measurements: measurements are made in this class using SI units. : distance between 2 points : space occupied. : the amount of matter in an object. : the force with which gravity pulls on a quantity of matter. Accuracy vs. Precision: Accuracy- Precision- (ex: a scale may be precise to the nearest 100 th of a gram, or +/- 0.01g ) 1

2 precision vs. accuracy increasing precision Density = increasing accuracy Example: What is the mass of 10 ml of a liquid that has a density of 3.76 g/ml? Temperature Conversions Temperature is a measure of the average kinetic energy in a system. = Kelvin = degree Celsius = degree Fahrenheit =Rankin (we won t use this one in this class K = o F = o C = Percentage Error: Calculate this value in labs where the accepted value is given. % error = ORGANIZING DATA: Data is organized and presented in tables, charts, and graphs. Graph - visual representation of data 1) 2) and axis labeled 3) for both the x and y axis 4) is evenly and correctly spaced for data 5) when appropriate LINE GRAPH: best for displaying data that. Independent Variable: Dependent variable: BAR GRAPH: useful when you want to data for several individual items. PIE CHART: ideal for displaying data that are. 2

3 Matter = anything with mass and volume Classification of Matter: Matter Law of Conservation of Matter (Mass): matter cannot be created or destroyed Law of Conservation of Energy: energy cannot be created or destroyed; it may, however, be transformed Virtually everything that is, is made up of atoms. Currently, we have about kinds of atoms. In the natural world there exists different kinds of atoms. The others have been artificially produced in laboratories. We call each kind of atom an, and we give it a specific name and symbol. Atoms are made up of, &. Protons and neutrons are in the nucleus of atoms. Electrons travel around the nucleus. Different kinds of atoms are different because they have different numbers of. We list elements by their, the # of protons. Physical properties: characteristics that can be observed without changing the identity of the substance. Examples: Physical change: a change in the physical form or properties of a substance that occurs without a change in composition. Examples: Chemical property: describes a substance s ability to change into a different substance. Examples: Chemical change: occurs when a substance changes composition by forming one or more new substances. (bonds are broken and bonds are formed) Example: Indications of a chemical change 3

4 Phases of Matter Kinetic Theory: All matter is made of atoms and molecules that act like tiny particles. These tiny particles are always in motion. The higher the temp., the faster the particles move. At the same temp., more massive (heavier) particles move slower than less massive (lighter) particles Solids: Definite Shape? Definite Volume? Molecules in a solid are and constantly vibrating. Liquids: Definite Shape? Definite Volume? Some liquids flow more easily than others. The resistance of a liquid to flow is called. o Honey has a high viscosity compared to water Gases: Definite Shape? Definite Volume? The particles in a gas are spread, but can be compressed by pumping them into a restricted volume. Changes of State: Energy Transfers: ENERGY is the ability to or move matter. Energy is when substances melt or evaporate. o NOTE: our bodies cool down when our sweat evaporates. Energy is when substances freeze or condense. Melting: Change of state from to Energy (heat) is by the substance that is melting. Freezing: Change of state from to Energy (heat) is by the substance that is undergoing freezing. Evaporation: Change of state at the surface of a as it passes to a Results from random motion of molecules that occasionally escape from the liquid surface. Energy (heat) is by the liquid. (Cooling of the liquid results) Can happen at any time. Condensation: Change of state from to Energy (heat) is by the substance that is melting. (Warming of the liquid results) Boiling: Change of state from to Occurs the liquid. Boiling point/temperature is determined by Energy is by the liquid 4

5 Phase Change Graph *Boiling & freezing points depend on the pressure. Phase Diagrams A phase diagram shows the equilibria pressure-temperature relationship among the different phases of a given substance. H 2O CO 2 AB = AC = AD = triple point = Point The point at which all 3 phases of a substance (solid, liquid, gas) can coexist at equilibrium. critical point = Point The combination of critical temperature and critical pressure. o critical temp = The temperature above which a gas cannot be liquefied. (H 2O=374ºC) o critical pressure = The pressure required to liquefy a gas at its critical temperature. (H 2O=218 atm) 5

6 Significant Figures IS THE LANGUAGE OF! Scientific Notation: scientist use special notation to express VERY LARGE or very small numbers. Ex: 300,000,000 m/sec = Ex: 1,007,000,000 sec = Ex: m = Significant Figures Atlantic - Pacific Rule: Decimal Present: Count from the Pacific side Decimal Absent: Count from the Atlantic side Start counting at the first non-zero number and count until you reach the end of the number Ex. I: Ex. II: 300,700 Significant Figures in Calculations When multiplying and dividing, limit and round to the least number of significant figures in any of the factors. Example: 23.0 x 432 x 19 = When adding and subtracting, limit and round your answer to the least number of decimal places in any of the numbers involved in the calculation. Example: = Determine how many significant figures are in each of the following measurements: L m g 4. 47,900 mm 5. 7,000,000,001 miles Hz 6

7 Round each of the following measurements off so that they each contain 3 significant figures (you may use scientific notation if you prefer): L 8. 9,047,022 mg g J Perform the prescribed operations. Round your answers to the proper number of significant figures. Include the appropriate units in your answer m / 3.21 s = g g g = m x m = 14. (5.83 m / 2.67 s) / 2.1 s = V x 6 = 7

8 Dimensional Analysis Given information: Unit conversion map: Convert 14 gallons to kildurkins: Convert 14 barrels to hogsheads: Convert 3.00 bushels to farkins: 8