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Chemistry….

Chemistry….

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Chemistry….

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  1. Chemistry…. The study of matter and the changes it undergoes

  2. 5 Major Areas of Chemistry • Analytical Chemistry- composition of substances. • Inorganic Chemistry- substances without carbon • Organic Chemistry- most substances containing carbon • Biochemistry- Chemistry of living things • Physical Chemistry- describes the behavior of chemicals (ex. stretching)

  3. 1.1 Chemistry’s impact on society: • Health & Medicine • Biotechnology • Energy & Environment • Materials & Technology • Agriculture- world’s food supply • The Environment- both risks and benefits involved in discoveries • Astronomy and Space Exploration

  4. 1.3 The Scientific Method • A logical approach to solving problems or answering questions. • Starts with observation- noting and recording facts • hypothesis- an educated guess as to the cause of the problem, or a proposed explanation

  5. Scientific Method • “controlled” experiment- designed to test the hypothesis • only two possible answers • hypothesis is right • hypothesis is wrong • Generates data & observations from experiments. • Modify hypothesis - repeat the cycle

  6. Observations • Cycle repeats many times. • The hypothesis gets more and more certain. • Becomes a theory • A thoroughly tested model that explains why things behave a certain way. Hypothesis Experiment

  7. Data Collection: • Qualitative vs. Quantitative • Examples??

  8. 1.4 What is Matter? • Matter is anything that takes up space and has mass. Everything, but energy! • Mass- amount of material or “stuff” in an object • Weight is due to gravity, and changes from location to location; mass is always constant.

  9. Types of Matter • Substance- a particular kind of matter - pure; is uniform (all the same) and has a definite composition (examples are elements & compounds) • water; gold • Mixture- more than one kind of matter; has a variable composition

  10. Substances • Elements- simplest kind of matter • cannot be broken down any simpler • all one kind of atom. • Compounds are substances that can be broken down only by chemical methods • When broken down, the pieces have completely different properties than the original compound. • Made of two or more atoms, chemically combined (not physical blend!)

  11. 10 Most Common Elements

  12. Mixtures • Physical blend of at least two substances; variable composition • Heterogeneous- mixture is not uniform in composition • Chocolate chip cookie, gravel, soil. • Homogeneous- same composition throughout; called “solutions” • Kool-aid, air, salt water • Every part keeps its own properties.

  13. Made of one kind of material Made of more than one kind of material Made by a chemical change Made by a physical change Definite composition Variable composition Compound or Mixture Compound Mixture

  14. Classification of Matter

  15. Element Compound Mixture Which is it?

  16. 1.5 States of Matter • Solid- matter that can not flow (definite shape) and has definite volume. • Liquid- definite volume but takes the shape of its container (flows). • Gas- a substance without definite volume or shape and can flow. • Vapor- a substance that is currently a gas, but normally is a liquid or solid at room temperature. (water vapor?)

  17. States of Matter Definite Volume? Definite Shape? Temp. increase Com-pressible? Small variation Solid YES YES NO Small variation. Liquid NO NO YES Large Variation Gas NO NO YES

  18. Condense Freeze Evaporate Melt Gas Liquid Solid

  19. 1.6 Properties • Words that describe matter (adjectives) • Physical Properties- a property that can be observed and measured without changing the composition. • Examples- color, hardness, m.p., b.p. • Chemical Properties- a property that can only be observed by changing the composition of the material. • Examples-volatile, flammable

  20. Types of Properties: • Extensive Properties: Dependent on quantity of matter ex: mass, volume • Intensive Properties: Independent of quantity ex: density, boiling point

  21. Physical Changes • A change that changes appearances, without changing the composition. • Ex. Boil, melt, cut, bend, split, crack • Boiled water is still water. • Chemical changes - a change where a new form of matter is formed. • Ex. Rust, burn, decompose, ferment

  22. Filtration: Physical Separation

  23. Distillation: Physical Separation

  24. 1.7 Measurement:International System of Units • The number is only part of the answer; it also need UNITS • The standards of measurement used in science are those of the Metric System

  25. International System of Units • Metric system is now revised as the International System of Units (SI), as of 1960 • Simplicity and based multiples of 10 • 10 base units (Know them…p.17 Table 1.3)

  26. International System of Units • Sometimes, non-SI units are used • Liter, Celsius, calorie • Some are derived units • Made by joining other units • Speed (miles/hour) • Density (grams/mL)

  27. Most Commonly Used Prefixes

  28. Volume • The space occupied by any sample of matter • Calculated for a solid by multiplying the length x width x height • SI unit = cubic meter (m3) • Everyday unit = Liter (L), which is non-SI

  29. Solid Volume Calculations 1 cm3 = 1 mL 1 dm3 = 1000 mL = 1 L 1 m3 = 1,000,000 mL = 1,000 L

  30. Volume Measuring Instruments • Graduated cylinders • Graduated Pipet • Buret • Volumetric Flask • Syringe

  31. Volume from Water Displacement

  32. Units of Mass • Mass is a measure of the quantity of matter • Weight is a force that measures the pull by gravity- it changes with location • Mass is constant, regardless of location

  33. Working with Mass • The SI unit of mass is the kilogram (kg), even though a more convenient unit is the gram • Measuring instrument is the balance or scale

  34. Density • The formula for density is: mass volume • Common units are g/mL, or possibly g/cm3, (or g/L for gas) • Density is an intensive, physical property Density =

  35. Density and Temperature • What happens to density as the temperature increases? • Mass remains the same • Most substances increase in volume as temperature increases • Thus, density generally decreases as the temperature increases

  36. Density and water • Water is an important exception • Over certain temperatures, the volume of water increases as the temperature decreases • Does ice float in liquid water? • Why?

  37. Temperature • Heat moves from warmer object to the cooler object • Remember that most substances expand with a temp. increase • Basis for thermometers

  38. Temperature scales • Celsius scale- named after a Swedish astronomer • Uses the freezing point(0 oC) and boiling point (100 oC) of water as references • Divided into 100 equal intervals, or degrees Celsius

  39. Temperature scales • Kelvin scale (or absolute scale) • Named after Lord Kelvin • K = oC + 273 • A change of one degree Kelvin is the same as a change of one degree Celsius • No degree sign is used

  40. 3 most common temp. scales • 0 K is called absolute zero, and equals –273 0C

  41. Conversion Formulas • K = 0C + 273 • 0F = 9/5(0C) + 32 • 0C = 5/9 (0F – 32)

  42. 1.8 Handling Numbers How do you know what number to round your calculation answers to? Significant figures: Determining which numbers are meaningful in a measurement or calculated quantity.

  43. Working with Scientific Notation • Regardless of magnitude: all numbers can be expressed in formula N x 10n N = number between 1 and 9.9 N = positive or negative whole # Ex: Express 0.000000456 in scientific notation Answer: 4.56 X 10-7

  44. Working with Scientific Notation • Do you know how to use your calculator when you have numbers in scientific notation????

  45. Significant Figures • Significant figures in a measurement include all of the digits that are known, plus a last digit that is estimated or uncertain. **This is what you did when you read the volume from the glassware in lab.

  46. Significant Figures • Rules: (page 24: Know 1-5) 1.) Any non-zero digit is significant Ex: 1.2345 = 5 sig. figs 2.) Zeros between non-zero digits are significant Ex: 1.2340567 = 8 sig. figs 3.) Zeros to the left of the first non-zero digit are not significant Ex: 0.00123456 = 6 sig. figs

  47. Significant Figures 4.) All zeros to the right of the decimal point are significant if they follow a non-zero number Ex: 4.560000 = 7 sig. figs 0.00100 = 3 sig. figs 5.) #’s without decimals present ambiguous info. Always use scientific notation to clear up problems. Ex: 56,700 = ? sig. figs 5.670 x 104 = 4 sig. figs

  48. Significant Figures Try These: How many sig. figs? A.) 1,245 B.) 1,245,000.15 C.) 0.00001 D.) 0.0004560 E.) 5.090 x 10-5

  49. Sig. fig. calculations • Addition and Subtraction • The answer should be rounded to the same number of decimalplaces as the least number in the problem

  50. Addition & Subtraction Examples: 1.) 4.56 cm + 3.1 cm= Answer: 7.7 cm 2.) 0.4567 L – 0.00654 L = Answer: 0.4502 L 3.) 450 g + 1.04 g= Answer: 451 g