Welcome to Chemistry

Transcription

1 Welcome to Chemistry

2 Introduction to Chemistry

3 Exit Question What kind of skills and strategies did you need to be successful in this class activity?

4 Day 2 9/10/13 QOD: What are my goals in this course? Do Now: Get a course syllabus and a student contract sheet.

5 My Goals for the Year:

6 We want S.M.A.R.T. goals Specific Measurable Attainable Realistic Timely

7 Exit Question Brainstorm some strategies to ensure success in this class.

8 Day 3 9/11/13 QOD: How do we measure in science? Do Now: What is chemistry? Write at least one idea down in your notes.

9 Chemistry is the science that studies matter and energy For a few thousand years people have asked how the world around them works and what the material things they see are made of Democritus (about BC) Philosopher who espouses the idea of atomism In modern times, the study of matter and energy has been pursued using more scientific approaches

10 Why is it often helpful to express numbers in Scientific Notation? Large numbers move the decimal point to the left until only one digit remains to the left. Next indicate the number of moves as the exponent of the 10 part of the number Example: 3,540,000 is written as 3.54 x 10 6

11 Why is it often helpful to express numbers in Scientific Notation? Small numbers move the decimal point to the right until only 1 digit is to the left of the decimal. Next, indicate the number of moves as the negative exponent of the 10 Example becomes 5.67 x 10-7

12 Thought for Food How do we express numbers in scientific notation? Why do we use scientific notation?

13 Exit ticket Write the following numbers in scientific notation: = =

14 Day 4 9/12/13 QOD: How do we measure in science? Do Now: Compare the measurements by using < > or =. 35 cm 1 m 1 dl 104 ml 250 g 25 dag Explain your answers.

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16 Measurement-The International System of Units Length-meter, m; distance that light travels in 1/299,792,458 of a second or about 3.3 feet Mass (amount of material in an object)-kilogram, kg; about 2.2 lbs on Earth

17 Weight vs. Mass Weight force of gravity pulling on an object; we rarely use this in chemistry Note: mass is always constant, but weight changes depending on where an object is Trivia: What is the easiest way to loose some weight within matters of hours (without any exercise)?

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19 Area and Volume Area since you get area by multiplying length (in meters, m) by width (also in meters, m), area has units of meters 2 Volume since you get volume by multiplying length x width x thickness, volume has units of meters 3 (in chemistry most volumes are given in liters, L; a liter is 1/1000 of a m 3

20 Celsius or Kelvin? Temperature measured in Celsius, C, or Kelvins, K; to convert C to K, simply add 273; 0 C is the freezing point of water; therefore in Kelvin the freezing point is 273 K 100 C is the boiling point of water. Question: at what Kelvin temperature does it boil?

21 Do Now: Day 5 9/13/13 (FRIDAY ) QOD: How do we do conversions between different metric units? Use KHDuDCM to solve the following problems: 1. 78g = kg km = cm L = ml

22 Metric Prefixes Milli- 1/ mm in 1 m Centi- 1/ cm in 1 m Deci- 1/10-10 dm in 1 m Deka m in 1 dam Hecto m in 1 hm Kilo m in 1 km Metric.html

23 Metric Measuring Bonanza Work with your partner to complete the task. Part A: 1. 2pts 2.1 pt 3. 2 pts Part B: 1. 3pts 5. 5pts Total points: pts 3. 1 pt 4. 2 pts

24 Measuring Metric Activity Work with a partner. 1. Measure the dimensions (length, width, and depth) of your binder. 2pts 2. Mass your binder. 2pts 3. Calculate the Area of the front of your binder. 4pts 4. Calculate the Volume of your binder. 6pts 5. Calculate the density of your binder. 6Pts SHOW ALL WORK!

25 Connection Others these are used a lot in cell and molecular biology and in biochemistry; they are extremely small amounts Pico 1 x Nano 1 x 10-9 Micro 1 x 10-6 Trivia: How big is a radius of an average cell in your body?

26 King Hector Drinks m Delicious Chocolate Milk L g

27 Exit Question Do the following conversions: 4 kg = g 7.8dL = L 23.9 km = cm

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29 Day 6 9/16/13 Monday QOD: What is the difference between precision and accuracy? CCLS RST , 9 Do Now: Give the SI units for length, mass, area, volume, and temperature. A room is 2.56 m long. How many is it in hm km cm mm Challenge: How many calories are in 45kcal?

30 Why is reliability important in measurements? Suppose, you want to get new carpeting in your room. You are very busy, and you ask two of your friends to do the measuring for you. They come back with two different answers: 24.6 meter squared 20 meter squared The difference means you need to pay more or less money and the carpet might not be large enough. Which friend will you trust did the measuring right?

31 Precision of measurements Precision if you measure something several times it should come out to the same value again and again It also describes the place value to which a measurement is made. For instance, a measurement of m is more precisely measured than a measurement of 1.0 m.

32 Accuracy of measurements Accuracy how close a measurement is to being true You must calibrate a measuring device before using it to make sure it is correct; for example, to calibrate a scale, you measure an object with a known mass and adjust the scale if necessary

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34 Significant Figures: certain vs. estimated digits Suppose you are measuring the length of an object with a ruler that has millimeters on it. You find that the length is cm +/- 0.01cm (or mm +/- 0.1mm) Now, you are only certain of the first 3 digits-123; the last digit, 4 is an estimate or an uncertain digit because the ruler does not measure 0.4 mm

35 Example: In the diagram below, the thermometer reads somewhere between 25 C and 30 C. We could estimate it at 27 C, but the 2 nd digit is uncertain. 1

36 Garbage in = Garbage out Principle When you add, subtract, multiply or divide measurements, you can only be as precise as the least precise measurement

37 Significant Figures or Digits The concept of Significant Figures is a way to communicate how precisely you measured your data If you made poor measurements, any calculations using these measurements will be of limited precision

38 Rules for Significant Digits Non-zero digits are always significant. Exp: 43.2 has 3 significant digits All final zeros after a decimal point are significant. Exp: has 3 significant digits

39 More Rules for Significant Digits Zeros between two other significant digits are always significant. Exp: 3005 has 4 significant digits Zeros used to space the decimal point are not significant. Exp: has 1 significant digit 3000 has 1 significant digit

40 Some More Rules for Significant Digits... Zeros at the end of a number that has no decimal point may or may not be significant. Exp: 240 has either 2 or 3 significant digits 2400 has either 2, 3 or 4 significant digits Scientists usually eliminate this ambiguity by writing these types of numbers in Scientific Notation

41 Note for Significant Digits Occasionally you will see numbers written like 10. or 20. with no zero after the decimal point. This implies that there are 2 significant digits in this measurement. Exp: 10.0 and have 3 and 4 significant digits respectively. What???!!! Arrrrgh...

42 Atlantic/ Pacific shortcut If a decimal point is absent, start counting from the Atlantic (right) side Start with the first nonzero digit Don t count zeros at the end EXP: 3,201,000 has at least 4 significant digits (it may turn out that the 3 zeroes at the end are also significant, but we can not really tell) 56905

43 Atlantic/ Pacific shortcut If a decimal point is present, count from the Pacific (Left) side; start counting with the first non-zero digit EXP:

44 Exit ticket Determine the number f significant figures in each number: HW: do the odd problems on page 1 of the Significant figures and operations sheet

45 Day 7 9/17/13 QOD: How do we do calculations with significant digits? CCLS: RST ,9 Do Now: Quiz: do the following conversions: cm = m Per L = ml kg = g Compare the measurements by using < > or = ml 5 dl g 400dag

46 Day 7 9/17/13 QOD: How do we do calculations with significant digits? CCLS: RST , 9 Do Now: Quiz: do the following conversions: m = mm Per ml = L kg = g Compare the measurements by using < > or = dl 3500mL g 40dag

47 Day 7 9/17/13 QOD: How do we do mathematical operations with significant digits? CCLS: RST ,9 Do Now: Quiz: do the following conversions: mm = m Per ml = L g = kg Compare the measurements by using < > or = L 3500cL 5. 40g 3.4dag

48 Significant Digits and Addition and Subtraction Rule: In addition and subtraction the result can have no more decimal places than the measurement with the fewest number of decimal places

49 Significant Digits and Addition and Subtraction Example: = However, 12.5 is the least precise number, measuring only to the tenths place. Therefore the answer should only be recorded to the tenths place; The same method is used for subtraction

50 Significant Digits and Multiplication and Division In multiplication and division the result must have the same number of significant digits as the measurement with the fewest significant digits Example: 4.33 x 6.2 = has only 2 significant digits; therefore, the product should have only 2 significant digits; it should be 27

51 Calculations with Multiple Steps When a calculation has multiple steps, make sure you retain 1 extra digit past the significant digits when you write down the answers to the intermediate steps. This minimizes the error due to rounding these intermediate answers.

52 Example A block has a length of 10.05cm, a width of 3.40 cm and a height of 1.2cm. Its mass is 420g. What is the density of the block? Step 1: Find the volume 10.05cm x 3.40cm x 1.2cm = cm 3 There should only be 2 significant figures in the answer + 1 additional digit since this is an intermediate step so the answer should be recorded as: Volume = 41.0cm 3

53 Step 2: Find the Density Density = mass/volume Density = 420g/ 41.0cm 3 = g/cm 3 = 10. g/cm 3 Another way to deal with this is to leave the numbers from the intermediate steps in your calculator and never round anything but the final answer.

54 Precision if you measure something several times it should come out to the same value again and again Accuracy how close a measurement is to being true

55 Activity: Sig. fig. competition Determine the number of significant digits in the following numbers: Bonus: 1.78 x 10 3

56 Exit ticket Share results and correct answers.

57 Day 8 9/18/13 QOD: How do we calculate percent error? CCLS RST ,9 Do Now: Solve the following, and express the results in the correct number of significant digits = x 9.32 = =

58 Activity Green Book How does percent error relate to accuracy? Read pages: Do Set 1 questions to practice percent error. However, the real value for the volume is 50 liters. What is the percent error?

59 Exit Slip AA student made a mistake when measuring the volume of a big container. He found the volume to be 65 liters. However, the real value for the volume is 50 liters. What is the percent error? However, the real value for the volume is 50 liters. What is the percent error?

60 Day 9 9/19/13 QOD: How do we describe different phases of matter? Do Now: What do I need to know for the assessment tomorrow? Take out your Unit 1 Topic Goal sheet. Check HW

61 Try yourself Metric Measurements 1. Do the following conversions. 5.3 m = cm 44 C = Kelvin 200 mm = km 67 dg = g 17 L = ml 2. Determine the number of significant figures: a) b) c) d) 7.9 x 10 9

62 Phases of Matter The term phase refers to the gas (g), liquid (l) or solid (s) forms of matter When a substance goes from one phase to another there is either an absorption or a release of heat energy The phase that a substance is in also depends upon the pressure that is acting on the substance

63 Solid Phase Atoms or molecules that make up the substance are in a fixed position While these atoms or molecules can t move around freely, they are free to vibrate This vibration increases as the temperature increases

64 Solids Density = mass/volume A) Crystals-particles in a crystal vibrate but they keep their regular pattern B) Melting Point-temperature at which a solid will change to a liquid at 1 atm of pressure

65 Phases of matter 1. Definite shape and volume Solids 2. Particles very close together, do not move 3,Crystalline structure

66 Liquid Phase The atoms or molecules are vibrating, translating, and rotating, but there is still a stronger attraction between these particles than there is in a gas They also take the shape of the container they are in The liquid in a container stays in the container even if its top is open because of this stronger attraction

67 Liquids 1. Definite volume and take the shape of the container 2. Particles are still close together and move while touching each other 3. No regular pattern or arrangement of molecules

68 Sublimation Occurs when certain substances change from solids directly into gases, without passing into a liquid state Substances that undergo sublimation have high vapor pressures and low intermolecular attractions Examples are dry ice, iodine crystals and naphthalene

69 Gaseous Phase The molecules are undergoing Translation ( that is, the attractions between the molecules are broken and the molecules are able to move about one another very freely) The molecules also undergo Rotation and Vibration

70 1.No definite shape and no definite volume 2.Particles are very far apart and move all over 3.Total disorder(entropy)- particles move in all directions

71 Day 10 9/20/13 QOD: What do I need to know about the metric system, and significant figures? Do Now:Get ready for the assessment

72 Heating Curve

73 Day 12 9/25/12 QOD: How do we distinguish between chemical and physical change? Do Now: Take out a writing utensil, and put everything else away from your desk. Bags/backpacks go under the seat.

74 How do we distinguish between chemical and Properties of substance physical properties? Are characteristics that can be used to identify it Physical Properties Chemical properties- Can be recognized without changing the substance to anything else Ex. Color, phase, hardness, solubility odor, density, boiling point, melting point, conductivity Describe how a substance reacts to form new substance. Ex. Does it -burn?, - react with water?, -react with acid?

75 How do we distinguish between chemical and physical properties? Physical Change Chemical properties- No chemical bonds are broken; no new substance is created. Chemical bonds are broken, and rearranged; new substance is created.

76 Exit Slip Write an example for chemical and physical change.