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Que es la Química, Método Científico

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  • 1. 1
    Chapter 1 Chemistry in Our Lives
    1.1 Chemistry and Chemicals
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 2. 2
    Definition of Chemistry
    Science devoted to the study of matter. It is the study of substances in terms of
    • Composition What is it made of?
    • 3. Structure How is it put together?
    • 4. Properties What characteristics does it
    have?
    • Reactions How does it behave with
    other substances?
  • 5. 3
    Chemistry
    Chemistry happens when
    • A car is started
    • 6. Tarnish is removed from silver
    • 7. Fertilizer is added to help plants grow
    • 8. Food is digested
    • 9. Electricity is produced from burning natural gas
    • 10. Rust is formed on iron nails
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 11. Chemistry and sustainable development
    Degradable plastics
    Organic fertilizers
    Solar energy
    Solar cars
    Clean industry
    Insulators
    4
  • 12. 5
    Chemicals
    Chemicals are substances used or produced by a chemical process.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 18. 6
    Chemicals in Toothpaste
    Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings
  • 19. 7
    Learning Check
    Which of the following items contain chemicals?
    A. Fertilizers
    B. Vitamins
    C. Happiness
    D. Iron nails
    E. Paints
  • 20. 8
    Solution
    Which of the following items contain chemicals?
    A. Fertilizers contain chemicals
    B. Vitamins contain chemicals
    C. Happiness does not contain chemicals
    D. Iron nails contain chemicals
    E. Paints contain chemicals
  • 21. Substance
    Substance- chemical that consists of one type of matter and always has the same composition and properties
    9
  • 22. 10
    Chapter 1 Chemistry in Our Lives
    1.2
    Scientific Method: process used by scientists to explain observations in nature.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 23. 11
    The scientific methodinvolves:
    Observations
    • Facts obtained by observing and measuring events in nature.
    Hypothesis
    • A statement that explains the observations. (educated guess)
    Experiments
    • Procedures that test the hypothesis.
    Theory
    • A model that describes how the observations occur using experimental results.
  • 12
    Summary of the Scientific Method
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 24. 13
    Everyday Scientific Thinking
    Observation:The sound from a CD in a CD player skips.
    Hypothesis 1:The CD player is faulty.
    Experiment 1: When I replace the CD with another one, the sound from this second CD is OK.
    Hypothesis 2:The original CD has a defect.
    Experiment 2:When I play the CD in another player, the sound still skips.
    Theory: My experimental results indicate the
    original CD has a defect.
  • 25. Scientific method
    State the problem (like a question)
    Hypothesis (suggest an answer to a problem)
    (If _ind var___ then _dep var___)
    Plan experiment
    Gather data
    Interpret data (look for patterns or trends)
    Conclusion, plan future work
    Publish results
  • 26. Experiment
    Way of testing a hypothesis
    Has an independent and a dependent variable
    Independent variable- you define it, causes a change in another
    Dependent variable- changes in response to the ind. Var.
    Control group - reference to find out if there were any changes in the experimental groups.It has all the same elements except the Ind. Var
  • 27. Tránsito de San Pedro wants to establish if the installation of radars will affect the average velocity of cars driving through MoronesPrieto.
    establish the problem (Will radars affect the velocity of cars?)
    Present the hypothesis (If there are radars in specific locations then cars will decrease their speed)
    Design the experiment (install radars in locations and measure speed with and without radars)
    identify independent (radars in specific locations)
    dependent variable (speed of cars)
    state the control group. (locations without radars)
  • 28. Carol is a soccer player. She told Mark that Adidas training shoes have a greater performance than Nike training shoes, in the soccer field.
    establish the problem
    Present the hypothesis
    Design the experiment
    identify dependent and independent variable
    state the control group.
  • 29. 18
    Learning Check
    The step of scientific method indicated in each is
    1) observation 2) hypothesis
    3) experiment 4) theory
    A. A blender does not work when plugged in.
    B. The blender motor is broken.
    C. The plug has malfunctioned.
    D. The blender does not work when plugged into a different outlet.
    E. The blender needs repair.
  • 30. 19
    Solution
    The step of scientific method indicated in each is
    1) observation 2) hypothesis
    3) experiment 4) theory
    A. (1) A blender does not work when plugged in.
    B. (2) The blender motor is broken.
    C. (2) The plug has malfunctioned.
    D. (3) The blender does not work when plugged
    into a different outlet.
    E. (4) The blender needs repair.
    Cw-Do from page 9 problems: 1.12-1.14
  • 31. 20
    Chapter 2 Measurements
    2.1
    Units of Measurement
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 32. 21
    Measurement
    You make a measurement
    every time you
    • Measure your height.
    • 33. Read your watch.
    • 34. Take your temperature.
    • 35. Weigh a cantaloupe.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 36. 22
    Measurement
    In a measurement
    • A measuring tool is used to compare some dimension of an object to a standard.
    • 37. Of the thickness of the skin fold at the waist, calipers are used.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 38. 23
    Stating a Measurement
    In a measurement, a number is followed by a unit.
    Observe the following examples of measurements:
    Number Unit
    35 m
    0.25 L
    225 kg
    3.4 hr
  • 39. 24
    The Metric System (SI)
    The metric system or SI (international system) is
    • A decimal system based on 10.
    • 40. Used in most of the world.
    • 41. Used everywhere by scientists.
  • 25
    Units in the Metric System
    In the metric (SI) system, one unit is used for each
    type of measurement:
    Measurement Metric SI
    length meter (m) meter (m)
    volume liter (L) cubic meter (m3)
    mass gram (g) kilogram (kg)
    time second (s) second (s)
    temperature Celsius (C) Kelvin (K)
  • 42. 26
    Volume Measurement
    Volume
    • Is the space occupied by a substance.
    • 43. Has the unit liter (L) in metric system.
    • 44. Uses the unit m3(cubic meter)in the SI system.
    • 45. Is measured using a graduated cylinder.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 46. 27
    Mass Measurement
    The massof an object
    • Is the quantity of material it contains.
    • 47. Is measured on a balance.
    • 48. Has the unit gram(g)in the metric system.
    • 49. Has the unit kilogram(kg)in the SI system.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 50. 28
    Temperature Measurement
    Thetemperature of a substance
    • Indicates how hot or cold it is.
    • 51. Is measured on the Celsius (C) scale in the metric system.
    • 52. In the SI system uses the Kelvin(K) scale.
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 53. 29
    Time Measurement
    Time measurement
    • Has the unit second(s) in both the metric and SI systems.
    • 54. Is based on an atomic clock that uses a frequency emitted by cesium atoms.
    Copyright © 2005 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 55. 30
    For each of the following, indicate whether the unit describes 1) length, 2) mass, or 3) volume.
    ____ A. A bag of onions has a mass of 2.6 kg.
    ____ B. A person is 2.0 m tall.
    ____ C. A medication contains 0.50 g aspirin.
    ____ D. A bottle contains 1.5 L of water.
    Learning Check
  • 56. 31
    For each of the following, indicate whether the unit describes 1) length, 2) mass, or 3) volume.
    2 A. A bag of onions has a mass of 2.6 kg.
    1 B. A person is 2.0 m tall.
    2 C. A medication contains 0.50 g aspirin.
    3 D. A bottle contains 1.5 L of water.
    Solution
  • 57. 32
    Learning Check
    Identify the measurement with an SI unit.
    A. John’s height is
    1) 1.5 yd 2) 6 ft 3) 2.1 m
    B. The race was won in
    1) 19.6 s 2) 14.2 min 3) 3.5 hr
    C. The mass of a lemon is
    1) 12 oz 2) 0.145 kg 3) 0.6 lb
    D. The temperature is
    1) 85C 2) 255 K 3) 45F
  • 58. 33
    Solution
    Identify the measurement with an SI unit.
    A. John’s height is
    3) 2.1 m
    B. The race was won in
    1) 19.6 s
    C. The mass of a lemon is
    2) 0.145 kg
    D. The temperature is
    2) 255 K
  • 59. 34
    STEP 1 State the given and needed units.
    STEP 2 Write a plan to convert the given unit to the
    needed unit.
    STEP 3 Write equalities/conversion factors that connect the units.
    STEP 4 Set up problem with factors to cancel
    units and calculate the answer.
    Unit 1 x Unit 2 = Unit 2
    Unit 1
    Given Conversion Needed
    unit factor unit
    Guide to Problem Solving (GPS)
  • 60. 35
    Setting up a Problem
    How many minutes are 2.5 hours?
    given unit = 2.5 hr
    needed unit = ? min
    plan= hr min
    Set up problem to cancel units (hr).
    given conversion needed
    unit factor unit
    2.5 hr x 60 min = 150 min
    1 hr
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 61. 36
    A rattlesnake is 2.44 m long. How long is the snake
    in centimeters?
    1) 2440 cm
    2) 244 cm
    3) 24.4 cm
    Learning Check
  • 62. 37
    A rattlesnake is 2.44 m long. How long is the
    snake in centimeters?
    2) 244 cm
    given conversion needed
    unit factor unit
    2.44 m x 100 cm = 244 cm
    1 m
    Solution
  • 63. 38
    • Often, two or more conversion factors are required to obtain the unit needed for the answer.
    Unit 1 Unit 2 Unit 3
    • Additional conversion factors can be placed in the setup to cancel each preceding unit
    Given unit x factor 1 x factor 2 = needed unit
    Unit 1 x Unit 2 x Unit 3 = Unit 3
    Unit 1 Unit 2
    Using Two or More Factors
  • 64. 39
    How many minutes are in 1.4 days?
    Given unit: 1.4 days Needed unit: min
    Plan: days hr min
    Equalties: 1 day = 24 hr
    1 hr = 60 min
    Set up problem:
    1.4 days x 24 hr x 60 min = 2.0 x 103 min
    1 day 1 hr
    Example: Problem Solving
  • 65. 40
    • Be sure to check your unit cancellation in the setup.
    • 66. The units in the conversion factors must cancel to give the correct unit for the answer.
    What is wrong with the following setup?1.4 day x 1 day x 1 hr
    24 hr 60 min
    Units = day2/min is Not the needed unit
    Units don’t cancel properly.
    Check the Unit Cancellation
  • 67. More units
    Area m2 = m x m
    Volume m3 = m x m x m
    Density mass/volume
    g/mL or Kg/L
    41
  • 68. K = oC + 273
    Ex
    23 oC = _______ K
    135 K = ________ oC
    1L = 1 dm3
    1 m3 =1000L
    Ex 27 m3 = ________ L
    42
  • 69. 43
    Osmium is a very dense metal. What is its
    density in g/cm3 if 50.0 g of osmium has a
    volume of 2.22 cm3?
    1) 2.25 g/cm3
    2) 22.5 g/cm3
    3) 111 g/cm3
    Learning Check
  • 70. 44
    Given: mass = 50.0 g volume = 2.22 cm3
    Plan: Write the density expression.
    D = mass
    volume
    Express mass in grams and volume in cm3mass = 50.0 g volume = 2.22 cm3
    Set up problem using mass and volume.
    D = 50.0 g = 22.522522 g/cm3
    2.22 cm3
    = 22.5 g/cm3
    Solution
  • 71. 45
    Volume by Displacement
    • A solid completely submerged in water displaces its own volume of water.
    • 72. The volume of the solid is calculated from the volume difference.
    45.0 mL - 35.5 mL
    = 9.5 mL = 9.5 cm3
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 73. 46
    Density Using Volume Displacement
    The density of the object is
    calculated from its mass and
    volume.
    mass = 68.60 g = 7.2 g/cm3
    volume 9.5 cm3
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 74. 47
    Sink or Float
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
    • Ice floats in water because the density of ice is less than the density of water.
    • 75. Aluminum sinks because its density is greater than the density of water.
  • 48
    Which diagram correctly represents the liquid layers in the cylinder? Karo (K) syrup (1.4 g/mL), vegetable (V) oil (0.91 g/mL,) water (W) (1.0 g/mL)
    1 2 3
    K
    W
    V
    V
    W
    K
    W
    V
    K
    Learning Check
  • 76. 49
    1)
    vegetable oil 0.91 g/mL
    water 1.0 g/mL
    Karo syrup 1.4 g/mL
    V
    W
    K
    Solution
  • 77. 50
    Chapter 2 Measurements
    2.2
    Scientific Notation
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 78. 51
    Scientific Notation
    Scientific notation
    • Is used to write very large or very small numbers.
    • 79. For the width of a human hair of 0.000 008 m is written as
    8 x 10-6m
    • For a large number such as 2 500 000 s is written as
    2.5 x 106s
    Copyright © 2008 by Pearson Education, Inc.
    Publishing as Benjamin Cummings
  • 80. 52
    Scientific Notation
    • A number written in scientific notation contains a coefficient and a power of 10.
    coefficient power of ten coefficient power of ten
    1.5 x 102 7.35 x 10-4
    • To write a number in scientific notation, the decimal point is moved after the first digit.
    • 81. The spaces moved are shown as a power of ten.
    52 000. = 5.2 x 1040.00378 = 3.78 x 10-3
    4 spaces left 3 spaces right
  • 82. 53
    Some Powers of Ten
    Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings
  • 83. 54
    Comparing Numbers in Standard and Scientific Notation
    Number in
    Standard Format Scientific Notation
    Diameter of the Earth
    12 800 000 m 1.28 x 107 m
    Mass of a human
    68 kg 6.8 x 101 kg
    Mass of a hummingbird
    0.002 kg 2 x 10-3 kg
    Length of a pox virus
    0.000 000 3 cm 3 x 10-7 cm
  • 84. 55
    Learning Check
    Select the correct scientific notation for each.
    A. 0.000 008
    1) 8 x 106 2) 8 x 10-6 3) 0.8 x 10-5
    B. 72 000
    1) 7.2 x 104 2) 72 x 103 3) 7.2 x 10-4
  • 85. 56
    Solution
    Select the correct scientific notation for each.
    A. 0.000 008
    2) 8 x 10-6
    B. 72 000
    1) 7.2 x 104
  • 86. 57
    Learning Check
    Write each as a standard number.
    A. 2.0 x 10-2
    1) 200 2) 0.00203) 0.020
    B. 1.8 x 105
    1) 180 000 2) 0.000 0183) 18 000
  • 87. 58
    Solution
    Write each as a standard number.
    A. 2.0 x 10-2
    3) 0.020
    B. 1.8 x 105
    1) 180 000