Chapter 1

1. Chapter 1 Chemistry: The Study of Change

2. Chemistry • How do we define Chemistry? • The study of how matter interacts with itself and other matter • Matter is anything that has mass and volume (which is anything other than nothing)

3. The Scientific Method(Monty Python Style) • The following video is a scene from the 1975 cult film “Monty Python and the Holy Grail” where a woman is accused of being witch; a clever parody of the whole medieval approach to science. The middle ages was a time when… • 1 - matters of law were settled with jousts • 2 - witches and heretics were tested for truth by means of torture • 3 - alchemists spent their lives trying to turn lead into gold • 4 - explorers searched for the fountain of youth • 5 - people believed that dense items fell to earth faster than lighter items merely because Aristotle had said it a thousand years earlier.

4. The Scientific Method(Monty Python Style) What is the fault in the procedure?

5. The Scientific Method • How is the scientific method organized? • Define the problem, prediction (hypothesis), controls and variables • Make observations • Qualitative • Quantitative • Record data • Interpret the data and modify hypothesis • Test the new hypothesis

6. The Method • Why is it important to have variables, but not too many? • Why is it important to continue testing your hypothesis? • Hard to tell which, if any, variables affected the result • Limit variables • Have many controls • More successful tests means it’s more valid • Removes error and doubt

7. Airplane Challenge • I challenge your team to build a paper airplane that will FLY the farthest distance. • Each team will build three planes. • 3 pieces of paper, 6 paper clips, scissors • Your team will test ONE variable to see which of your three prototypes will work the best. • In your observations, you must list 4 controls and 1 variable.

8. Airplane Challenge Before you fly! • What are you testing? • What is my first hypothesis? • What are 4 controls and my 1 variable? After you fly! • What did I observe after the test flights? • Please answer these questions in your notebook.

9. Classification • Please draw the graphic organizer below and then place the following terms into it: • Mixtures • Elements • Pure Substances • Homogeneous • Matter • Heterogeneous • Compounds

10. Classification

11. Classification • What is the difference between pure substances and mixtures? • Pure substances - chemical combination (bonded) with constant composition • Mixtures - physical combination of two or more substances

12. Classification • What is the difference between elements and compounds? • Elements - single atom or a chemical combination of the same element • Li or C60 • Compounds - chemical combination of two or more elements • H2O or CH4

13. Classification • What is the difference between homo/heterogeneous? • Homogeneous - physical combination that is uniform (same throughout) • Salt water • Heterogeneous - physical combination that is not uniform (different throughout) • Sandy water

14. Physical and Chemical Properties • What is the difference between a chemical and physical property? • Physical property can be measured/observed without changing the substance • Ex. Color, odor, phase, volume, mass... • Chemical property cannot be measured/observed without changing the substance

15. Physical and Chemical Properties Physical properties can be divided into what two categories? • Extensive – depends on how much matter you have • Mass • Volume • Intensive – does not depend on how much matter you have • Density • Temperature

16. Physical and Chemical Properties

17. Physical and Chemical Properties • Physical or chemical Property? • Boiling Point • Density • Reacts with water • Freezes at 20 degrees • 50 g • Does not react with dilute sulfuric acid • Physical • Physical • Chemical • Physical • Physical • Chemical

18. Physical and Chemical Properties • What does it mean to undergo a physical change? • One or more physical properties change, we change the appearance • Color change • Mass change • Phase change • The composition does not change • Ex. Ice and water vapor are still H2O

19. Physical and Chemical Properties What does it mean to undergo a chemical change? • Two or more substances reacted and a new substance was made • Ex. Rust • Cannot get the substance back without using a chemical reaction • Indicators could be: • A gas is produced • Light is produced • A solid precipitate forms

20. Physical and Chemical Properties • Physical/Chemical Change? • Ice melting • Cutting the grass • Souring milk • Baking a cake • Dissolving salt • Physical • Physical • Chemical • Chemical • Physical

21. Physical and Chemical Properties • Please create this table in your notebook :

22. Physical and Chemical Properties • I have two substances A and B. A is a purple solid which weighs approximately 13.6 grams. It is a hard substance that will not melt until heated to approximately 110 °C. A does not float in water and it likes to react with a metal substance called M. B is a clear liquid that does not react with M, but it will evaporate if heated to a temperature of 59 °C. B will react, however, with sulfuric acid to create blue gas and green colored slime. When substances A and B are combined, a new substance C is formed, which is a black liquid that smells like cheese and reacts with M. C decomposes in sunlight into a red toxic gas which smells like delicious strawberries. • What are two physical and chemical properties of A, B and C?

23. Factor-Label Method (Dimensional Analysis) Why is the factor-label method very important in chemistry? It allows us to easily convert between units using a series of fractions based on equivalencies

24. Factor-Label Method (Dimensional Analysis) How many different types are there? • Three types: • Two step - converting to or from a base unit • Multiple step - converting from a non-base unit to a non-base unit • Formula conversion • Ex. Celsius to Fahrenheit

25. Factor-Label Method (Dimensional Analysis) • Two-Step • Convert: • 2.5 cm to m • 5.08 g to kg • 3.21 L to ML • 0.19 mol to mmol • 6.7 µm to m

26. Factor-Label Method (Dimensional Analysis) • Multi-Step • Convert: • 0.04 mJ to kJ • 36.0 μL to pL • 5 mmol to kmol • 60 ms to μs • 5 atm to kPa

27. Factor-Label Method (Dimensional Analysis) Challenge #1 • Given the following conversion factors convert 1 fizzle to frizzles • 3 swizzles = 7 twizzles • 1 fizzle = 2 drizzles • 3 twizzles = 14 sizzles • 1 swizzles = 22 frizzles • 8 drizzles = 5 sizzles

28. Factor-Label Method (Dimensional Analysis) Challenge #2 • Jules Vern wrote a book called Twenty Thousand Leagues Under the Sea. Using the conversion factors below, convert 20,000 leagues to inches. • 12 in = 1 ft • 3 ft = 1 yd • 1 fathom = 2 yds • 1 mile = 5280 ft • 1 nautical mile = 6080 ft • 1 league = 3 nautical miles

29. Significant Figures (Sig figs) • Why are significant figures important? • Indicates how precise the measurement is • You are only as precise as your least precise measurement!

30. Significant Figures (Sig figs) • How do you determine what figures are significant? • Always counts: • Any non-zero number • 2132has four sig figs • Any zero between two non-zero numbers • 2002 has four sig figs – two 0’s and two 2’s

31. Significant Figures (Sig figs) • How do you determine what figures are significant? • Never counts: • All zeros in front of the first non-zero number • 0.0012 has two sig figs –1 and 2

32. Significant Figures (Sig figs) • How do you determine what figures are significant? • Sometimes counts: • Zeros at the end of a number are significantwhenever there is a decimal present • 0.075900 has 5 sig figs; the first two zeros do not count • 14000.has 5 sig figs • 14000.0has 6 sig figs

33. Significant Figures (Sig figs) • How do you determine what figures are significant? • Sometimes counts: • Zeros at the end of a number are not usuallysignificant when there is not a decimal point • 14,000 has only 2 sig figs

34. Significant Figures (Sig figs) • How many sig figs do the following numbers have? • 0.0013 • 1.20 • 0.0101010 • 450 • 350.0 • 2 sig figs • 3 sig figs • 6 sig figs • 2 sig figs • 4 sig figs

35. Significant Figures (Sig figs) • How do you add/subtract with sig figs? • Look at decimal places. Your answer should end in the same decimal place as your least precise measurement • 200.27 + 45.8 + 31.456 = • 277.5

36. Significant Figures (Sig figs) • How do you multiply/divide with sig figs? • What about mixed operations? • Your answer should have the same number of significant figures as the measurement with the fewest significant figures • 25.03 x 0.02 = • 0.5 • Follow sig fig rules for each step of the calculation

37. Significant Figures (Sig figs) • 100.1 + 34 = • 7.892 – 2.9 • 3.44 – 11 + 0.009 = • 1.23 x 4.0 = • (100.1)(10.00) / 0.01000 = • (100.0 + 23 + 99.99) / 89.99 = • 134 • 5.0 • -8 • 4.9 • 100100 • 2.48

38. Uncertainties • What is an uncertainty? • A measured value that cannot be determined exactly • Actual number could be above or below the measured reading • Error in precision

39. Uncertainties • How do we represent uncertainties? • Need range • Use +/- • Make it reasonable! • Examples • 25.2 +/- 0.1 mL • 23.0 +/- 0.5 °C • Depends on how precise your measuring device is

40. Precision vs. Accuracy • What is the difference between precision and accuracy? • Accuracy refers to how close a measurement is to the true or accepted value • Precision indicates how close together a group of measurements are to each other

41. Precision vs. Accuracy

42. Practice Problem • The table lists the results of temperature measurements of a beaker of boiling water. The standard temperature of boiling water is 100 °C. • Explain whether each thermometer was accurate, precise, neither or both.

43. Percent Error • What is percent error? • Used to determine how close you are to the actual values