Chemistry Day 37. Monday, December 10 th Tuesday, December 11 th, 2018

Transcription

1 Chemistry Day 37 Monday, December 10 th Tuesday, December 11 th, 2018

2 Do-Now: Reaction Types CN 1. Write down today s FLT 2. What does the Law of Conservation of Mass tell us? Aluminum oxide yields solid aluminum and oxygen gas 3. Write the chemical equation for the above word equation. Be sure to write your formulas carefully. 4. Balance the chemical equation. Show all work. Take out your planner and ToC

3 Quiz Protocol Noise Level 0 Eyes on your own paper You may use your reference sheet Check your answers Flip over when finished

4 FLT I will be able to describe and identify the five general types of chemical reactions by completing Reaction Types CN Standard HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction

5 Chemical Reactions

6 Notes Protocol Add assignment # Copy down all bolded ideas Noise level 0 Raise hand to question/comment Be prepared to pair-share-respond

7 Types of Chemical Reactions

8 Recall

9 Chemical Equations Chemical Equations = Represent chemical rxns Must be balanced (Law of Conservation of Mass)

10 Overview

11 Overview We can categorize reactions into five general types: Combination/Synthesis Decomposition Combustion Single displacement/replacement Double displacement/replacement

12 Combination Rxns

13 Combination Reactions Combine = put together Combination/Synthesis Rxn = A + B à AB

14 Combination Reactions Ca + O 2 à CaO SO 3 + H 2 O à H 2 SO 4

15 Combination Reactions We can predict the products, especially if the reactants are two elements Ex/ Mg + N 2 à?

16 Complete and Balance: 1. Ca + Cl 2 à

17 Combination Reactions Additional Notes: Some nonmetal oxides react with water to produce an acid (acid rain): SO 2 + H 2 O à H 2 SO 3 Some metallic oxides react with water to produce a base: CaO + H 2 O à Ca(OH) 2

18 Decomposition Rxns

19 Decomposition Reactions Decompose = fall apart Decomposition Rxn = AB à A + B

20 Decomposition Reactions NaCl Na + Cl 2 CaCO 3 CaO + CO 2 Energy (heat, sunlight, electricity, etc) is usually required

21 Decomposition Reactions We can predict the products for binary compounds (only two elements) Ex/ H 2 O

22 1. HgO Complete and Balance:

23 Combustion Rxns

24 Combustion Reactions Combustion means add oxygen Combustion Rxn = Normally, hydrocarbon + O 2 à CO 2 + H 2 O They can sometimes be difficult to balance

25 Combustion Reactions Ex/ C 4 H 10 + O 2 à

26 Try This One 1. C 2 H 2 + O 2 à

27 Single Replacement Rxns

28 Single Replacement Rxns AKA single displacement rxns Single Replacement Rxn = One element replaces another Metals replace metals Halogens replace halogens

29 Single Replacement Rxns Ex/ Na + KCl à K + NaCl Ex/ F 2 + LiCl à

30 Single Replacement Rxns Activity Series: Metals can only replace weaker metals Halogens use periodic table

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32 Single Replacement Rxns Can Ca replace Al? Can Sn replace Fe? Can Cu replace H? Can Zn replace Au?

33 Single Replacement Rxns Write no rxn if a rxn cannot occur

34 Can these rxns occur? If so, write and Al + HCl à balance them! Pb + KCl à

35 Double Replacement Rxns

36 Double Replacement Rxns Double Replacement Rxn = Two things replace each other Reactants must be two ionic compounds Ex/ NaOH + FeCl 3 à Fe(OH) 3 + NaCl Warning: Write out ions to figure out formulas!

37 Double Replacement Rxns Ex/ CuCl 2 + NaOH à

38 Complete and Balance: CaCl 2 + K 2 S à

39 How to recognize which type? Look at the reactants: X + Y à XY = Combination XY à X + Y = Decomposition A + BC à B + AC = Single replacement AB + CD à AD + BC = Double replacement Hydrocarbon + O 2 à CO 2 + H 2 O = Combustion

40 Chemistry Day 38 Wednesday, December 12 th Thursday, December 13 th, 2018

41 Do-Now: Chemical Change Notes 1. Write down today s FLT Write what reaction type is being represented below: 2. AB à A + B 3. CH + O 2 à H 2 O + CO 2 4. A + BC à B + AC 5. A + B à AB 6. AB + CD à AD + BC 7. Use a pro-talk sentence frame to describe the difference between single and double displacement reactions 8. Turn in your ToC if you haven t already Take out your planner and ToC

42 FLT I will be able to predict the products of chemical reactions by completing Eq/ Rxn Review Standard HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction

43 Recall

44 How to recognize which type? Look at the reactants: X + Y à XY = Combination XY à X + Y = Decomposition A + BC à B + AC = Single replacement AB + CD à AD + BC = Double replacement Hydrocarbon + O 2 à CO 2 + H 2 O = Combustion

45 Chemical vs. Physical Change

46 Matter Matter = Anything with mass and volume Matter can undergo physical and chemical changes What s the difference?

47 Matter A physical change does not change the identity of a substance It can change its properties What are some examples?

48 Matter Examples of physical changes: An ice cube melts Rubbing alcohol evaporates Dry ice sublimes into vapor

49 Matter A chemical change results in a rearrangement of atoms, changing the identity of the substance In other words, a chemical reaction has occurred Will substances always react with each other? How can you tell if a reaction occurs in the lab?

50 Signs of a Chemical Change

51 Signs of a Chemical Change 1. Production of an odor When a reaction occurs, an odor may be produced due to a reaction When eggs rot, a sulfuric smell is produced

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53 Signs of a Chemical Change 2. Change in Temperature When a reaction occurs, it may release or absorb heat Consequently, the reaction vessel may feel warm when heat is released, or cool when heat is being absorbed

54 Signs of a Chemical Change 2. Change in Temperature If a reaction in a beaker is absorbing heat, will it feel warm or cold to you? If a reaction in a beaker is releasing heat, will it feel warm or cold to you?

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56 Signs of a Chemical Change 3. Change in Color Many chemicals have different colors A change in color is often an indication of a chemical change However, not all color changes are chemical

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58 Signs of a Chemical Change 4. Production of Gas Sometimes reactions release products that are gaseous You may observe this as bubbles, fizzing, or even foaming

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60 Signs of a Chemical Change 5. Formation of a Solid Sometimes when two solutions are combined, a solid can form A precipitate = an insoluble solid that emerges from liquid solution This can appear as a cloudiness

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62 Pair-Share-Respond 1. Remind me what is matter again? 2. Distinguish between a physical and chemical change 3. Provide an example of a physical and chemical change 4. Identify the signs of a chemical change.

63 Activity Series

64 Chemistry Day 39 Wednesday, December 12 th Thursday, December 13 th, 2018

65 Do-Now: Reactions Quiz Do-Now 1. Write down today s FLT 2. Copy: S 8 + O 2 à SO 2 3. Identify the type of reaction in #2. 4. Balance the equation in #2. Show all work. 5. What is rounded to the nearest a. Hundredths b. Tenths c. Ones d. Tens e. Hundreds Take out your planner and ToC

66 Quiz Protocol Noise Level 0 Eyes on your own paper You may use your reference sheet Check your answers Flip over when finished

67 FLT I will be able to determine the number of significant figures in a measurement by completing Sig Figs Notes Standard HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction

68 Scientific Measurement

69 Sig Figs Cornell Notes Add assignment # Copy down all bolded ideas Noise level 0 Raise hand to question/comment Be prepared to pair-share-respond

70 Measurements

71 Measurements We often take measurements in chemistry labs

72 Measurements Are our measurements accurate? This depends on: The reliability of the measuring instrument the care with which it is read this is determined by YOU!

73 Video Notes Measurements Write down four facts or examples from the video clip

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75 Accuracy vs. Precision

76 Accuracy, Precision, and Error It is necessary to make good, reliable measurements in the lab Accuracy how close a measurement is to the true value Precision how close the measurements are to each other (reproducibility)

77 Precision and Accuracy Neither accurate nor precise Precise, but not accurate Precise AND accurate

78 Why Is there Uncertainty? Measurements are performed with instruments, and no instrument can read to an infinite number of decimal places Which of the balances below has the greatest uncertainty in measurement?

79 A Brief Review of Scientific Notation

80 Sig Figs

81 Significant Figures in Measurements Significant figures = all known digits plus one estimated digit Measurements must be reported to the correct number of significant figures.

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84 Significant Figures in Measurements If you don t use the correct sig figs, your answer is incorrect L

85 Rules for Sig Figs

86 Rules for Counting Sig Figs -Nonzero digits are always significant Ex/ sig figs

87 Rules for Counting Sig Figs -Leading zeroes are NOT significant Ex/ sig figs

88 Rules for Counting Sig Figs -Zeroes in between significant digits are also significant Ex/ sig figs

89 Rules for Counting Sig Figs Trailing zeroes are significant only if a decimal point is present Ex/ sig figs Ex/ sig figs

90 Rules for Counting Significant Figures Counted items & defined quantities have unlimited sig figs Counted items 23 people, or 425 thumbtacks Exactly defined quantities 60 minutes = 1 hour

91 1 M < 10 M x 10 n n is an integer

92 Pair-Share-Respond How many significant figures in the following? m à 5 sig figs kg à 4 sig figs 100,890 L à 5 sig figs 3.29 x 10 3 s à 3 sig figs cm à 2 sig figs 3,200,000 ml à 2 sig figs 5 dogs à unlimited This is a counted value

93 Significant Figures in Calculations In general a calculated answer cannot be more precise than the least precise measurement from which it was calculated. Ever heard that a chain is only as strong as the weakest link? Sometimes, calculated values need to be rounded off.

94 Rounding Calculated Answers 1. Determine how many sig figs are needed 2. Round your answer to the correct number of sig figs

95 Rounding Calculated Answers + and - Round to the number with the fewest decimal places Ex/12.25 m m m m

96 Rounding Calculated Answers and Round answer to the smallest # of sig figs present Ex/ 6.38 x 2.0 = à 13 (2 sig figs) Ex/2.10 meters x 0.7 meters = 1 meter

97 Pair-Share-Respond Calculation Calculator says: Answer 3.24 m x 7.0 m m 2 23 m g 23.7 cm g/cm g/cm cm x cm cm cm m 3.0 s m/s 240 m/s lb x 3.23 ft lb ft 5870 lb ft g x 2.87 ml g/ml 2.96 g/ml

98 Scientific Notation Review

99 Overview How wide is our universe? 210,000,000,000,000,000,000,000 miles That s 22 zeroes When numbers are this large, it is easier to write them in scientific notation à 2.1 x miles

100 1 M < 10 M x 10 n n is an integer

101 Overview Rules: 1. Move decimal pt. after the first nonzero digit, and include all significant digits 2. Count how many places you moved the decimal à that is your exponent 3. Moved left à positive exponent. Moved right à negative exponent. 4. Write as M 10 n

102 Overview 210,000,000,000,000,000,000,000 miles Place the decimal point after the first digit Between the 2 and the ,000,000,000,000,000,000,000.

103 Overview 2.10,000,000,000,000,000,000,000. Count how many places your decimal moved 23 I moved my decimal left, so my exponent is Positive 23 The answer in scientific notation is 2.1 x 10 23

104 Examples

105 Examples 1) Where would the decimal go to make the number be between 1 and 10? 9.02 The decimal was moved how many places? 8 I moved right, so my exponent is negative 9.02 x 10-8

106 Try These: Write in sci notation 1) ) 4,580,000 3)

107 Try These: Write in decimal form 4) ) )

108 Try These: Write in sci notation 7) x ) x ) x 10 4