Water,%20Water%20Everywhere

1
Water, Water Everywhere
2
Water as Liquid - Rainwater
3
Water as Solid - Iceberg
4
Snow and Snow Flakes
5
Water Vapor (Steam)
6
Water Cycle
7
Water Cycle
8
Water Molecule
9
Hydrogen Bonding in Water
10
What Makes Soils Rocks Have Different Colors
11
Where does Chemistry fit in?

• Chemistry is about the study of matters and the
  changes they undergo.
• Chemistry probes the fundamental units of matter
  in order to understand how and why they are what
  they are.
• Chemists always ask questions and try to find the
  answers.

12
The Central Science

• Chemistry is regarded as the central science.
• Chemistry is essential in understanding the
  various aspects of living and non-living things
• It is essential in understanding natural and
  unnatural processes of nature.

13
What is Matter?

• The materials of the universe
• ? anything that has mass and occupies space

14
What Type of Change?

• Physical or Chemical processes
• Physical Change
• A process that alters the state of a substance,
  but not its fundamental composition.
• Chemical Change
• A process that alters the fundamental
  composition of the substance and, therefore, its
  identity.

15
The Scientific Approach

1. Making Observations/collecting Data
2. Formulating Hypotheses
3. Testing the Hypotheses
4. Revising the Hypothesis
5. Summarizing Hypotheses into a Theory
6. Summarizing observations or natural behavior into
   a Scientific Law

16
Steps in the scientific Method?

• Identify the Problems and ask Questions
• Develop a Hypothesis based on observations
• Test The Hypothesis
• (Design Perform Experiments)
• Collect more Data
• Analyze Results
• Make a Conclusion
• Suggest further studies on the subject.

17
Definitions of Terms in Scientific Methods

• Hypothesis-
• a plausible or logical statement that attempts
  to explain the observation or data.
• Theory -
• a set of (tested) hypotheses that explain a
  certain behavior of nature.
• Scientific Law -
• a concise statement about a natural phenomenon
  or behavior.

18
Measurements

• The Number System
• Decimal Numbers
• 384,400
• 0.08206
• Scientific Notations
• 3.844 x 105
• 8.206 x 10-2

19
Units of Measurements

• Units give meaning to numbers.
• Without Unit With Units
• 384,400 ? 384,400 km (very far)
• 384,400 cm (not very far)
• 0.08206 ? 0.08206 L.atm/(K.mol)
• 144 ? 144 eggs

20
English Units

• Mass ounce (oz.), pound (lb.), ton
• Length inches, feet, yards, miles
• Volume pints, quarts, gallons, in3, ft3, etc.
• Area acre, hectare, in2, ft2, yd2, mi2.

21
Metric Units

1. Mass milligram (mg), gram (g), kilogram (kg),
2. Length cm, m, km, mm, mm, nm,
3. Area cm2, m2, km2
4. Volume mL(cm3), dL, L,, m3.

22
SI Units

1. Mass kilogram (kg)
2. Length meter (m)
3. Area square meter (m2)
4. Volume cubic meter (m3)
5. Temperature Kelvin (K)
6. Energy Joule (J)
7. Charge Coulomb (C)
8. Time second (s)

23
Prefixes in the Metric System

• Prefix Symbol 10n Decimal Forms
• Giga G 109 1,000,000,000
• Mega M 106 1,000,000
• kilo k 103 1,000
• deci d 10-1 0.1
• centi c 10-2 0.01
• milli m 10-3 0.001
• micro m 10-6 0.000,001
• nano n 10-9 0.000,000,001

24
Accuracy and Precisionin Measurements

• Accuracy
• The agreement of an experimental value with the
  true or accepted value
• Precision
• The reproducibility of measurements of the same
  type

25
Accuracy and Precision
26
Errors in Measurements

• Random errors
• values have equal chances of being high or low
• may be minimize by taking the average of several
  measurements of the same kind
• Systematic errors
• Errors due to faulty instruments
• Reading is either higher or lower than the
  correct value by a fixed amount
• Weighing by differences can eliminate systematic
  errors of the faulty instruments.

27
Significant Figures

• All non-zero digits
• Example 453.6 has 4 significant figures.
• Captive zeros
• Example 1.079 has 4 significant figures.
• Trailing zeros if the decimal point is shown
• Example 1080 has 3 significant figures, but
  1080. or 1.080 x 103 has 4 significant figures.
• Leading zeros are not significant figures
• Example 0.02050 has 4 significant figures

28
How many significant figures?

1. 0.00239
2. 0.01950
3. 1.00 x 10-3
4. 100.40
5. 168,000
6. 0.082060
7. 144 eggs in a carton
8. Express one thousand as a value with two
   significant figures.

29
Rounding off Calculated values

• In Multiplications and Divisions
• Round off the final answer so that it has the
  same number of significant figures as the one
  with the least significant figures.
• Examples
• (a) 9.546 x 3.12 29.8 (round off from
  29.78352)
• (b) 9.546/2.5 3.8 (round off from 3.8184)
• (c) (9.546 x 3.12)/2.5 12 (round off from
  11.913408)

30
Rounding off Calculated values

• In Additions and Subtractions
• Round off the final answer so that it has the
  same number of digits after the decimal point as
  the data value with the least number of such
  digits.
• Examples
• (a) 53.6 7.265 60.9 (round off from 60.865)
• (b) 53.6 7.265 46.3 (round off from 46.335)
• (c) 41 7.265 5.5 43 (round off from 42.765)

31
Mean, Median Standard Deviation

• Mean average
• Example
• Consider the following temperature values
• 20.4oC, 20.6oC, 20.3oC, 20.5oC, 20.4oC, and
  20.2oC
• (Is there any outlying value that we can throw
  away?)
• No outlying value, the mean temperature is
• (20.4 20.6 20.3 20.5 20.4 20.2) 6
  20.4oC

32
Mean, Median Standard Deviation

• Median
• the middle value (for odd number samples) or
• average of two middle values (for even number)
• when values are arranged in ascending or
  descending order.
• For the following temperatures
• 20.4oC, 20.6oC, 20.3oC, 20.5oC, 20.4oC, and
  20.2oC,
• the median 20.4oC

33
Mean, Median Standard Deviation

• Standard Deviation, S
• (for n lt 10, Xi sample value mean
  value)
• Note calculated value for std. deviation should
  have one significant figure only.
• For above temperatures, S 0.1 Mean 20.4
  0.1 oC

34
Calculating Mean Value

• Consider the following masses of pennies (in
  grams)
• 2.48, 2.50, 2.52, 2.49, 2.50, 3.02, 2.49, and
  2.51
• Is there outlying value?
• Yes 3.02 does not belong in the group can be
  discarded
• Outlying values should not be included when
  calculating the mean, median, or standard
  deviation.
• Average (mean) mass of pennies is,
• (2.48 2.50 2.52 2.49 2.50 2.49 2.51)
  7 2.50 g

35
Calculating Standard Deviation

• _________________________
• -0.02 0.0004
• -0.00 0.0000
• 0.02 0.0004
• -0.01 0.0001
• 0.00 0.0000
• -0.01 0.0001
• 0.01 0.0001___
• Sum 0.0011
• ------------------------------------------

36
Mean and Standard Deviation

• The correct mean value that is consistent with
  the precision is expressed as follows
• 2.50 0.01

37
Using Q-test to retain or reject questionable
values

• Calculate Qcalc. as follows
• Qcalc.
• Compare Qcalc with Qtab from Table-2 at the
  chosen confidence level for the matching sample
  size
• If Qcalc lt Qtab, the questionable value is
  retained
• If Qcalc gt Qtab, the questionable value is can
  rejected.

38
Rejection Quotient

• Rejection quotient, Qtab, at 90 confidence level
• Sample size Qtab ___
• 4 0.76
• 5 0.64
• 6 0.56
• 7 0.51
• 8 0.47
• 9 0.44
• 10 0.41

39
Performing Q-test on Sample Data

• Consider the following set of data values
• 0.5230, 0.5325, 0.5560, 0.5250, 0.5180, and
  0.5270
• Two questionable values are 0.5180 0.5560 (the
  lowest and highest values in the group)
• Perform Q-test at 90 confidence level on 0.5180
• Qcalc. 0.13 lt 0.56
• (limit at 90 confidence level for sample size of
  6)
• We keep 0.5180.

40
Performing Q-test on questionable value

• Calculate rejection quotient for 0.5560
• Qcalc. 0.618 gt 0.56
• (limit at 90 confidence level for a sample of 6
  is 0.56)
• We reject 0.5560.

41
Calculate the mean using acceptable values

• Re-write the mean value to be consistent with the
  precision
• Mean 0.526 0.005

42
Calculating Standard Deviation

• ???????????????
• 0.5230 -0.0028 7.8 x 10-6
• 0.5325 0.0067 4.5 x 10-5
• 0.5250 -0.0008 6.4 x 10-7
• 0.5180 -0.0078 6.1 x 10-5
• 0.7270 0.0012 1.4 x 10-6
• S 1.16 x 10-4

43
Mean value must be consistent with the precision

• Standard deviation
• should have one significant digit only
• It shows where the uncertainty appears in mean
  value
• That is, which digit on the mean contains error
• The mean value should be rounded off at the digit
  where it becomes uncertain.
• Thus, the mean consistent with the precision will
  be
• 0.526 0.005
• (the mean value is precise up to the third
  decimal place)

44
Problem Solving by Dimensional Analysis

• Value sought value given x conversion factor(s)
• Example
• How many kilometers is 25 miles? (1 mi. 1.609
  km)
• Value sought ? km value given 25 miles
• conversion factor 1 mi. 1.609 km
• ? km 25 mi. x (1.609 km/1 mi.) 40. km

45
Unit Conversions

• (1) Express 26 miles per gallon (mpg) to
  kilometers per liter (kmpL).
• (1 mile 1.609 km and 1 gallon 3.7854 L)
• (Answer 11 kmpL)
• (2) If the speed of light is 3.00 x 108 m/s, what
  is the speed in miles per hour (mph)?
• (1 km 1000 m and 1 hour 3600 s)
• (Answer 6.71 x 108)

46
Temperature

• Temperature scales
• Celsius (oC)
• Fahrenheit (oF)
• Kelvin (K)
• Reference temperatures freezing and boiling
  point of water
• Tf 0 oC 32 oF 273.15 K
• Tb 100 oC 212 oF 373.15 K

47
Temperature Conversion

• Fahrenheit to Celsius
• (T oF 32 oF) x (5oC/9oF) T oC
• Example converting 98.6oF to oC
• (98.6 oF 32 oF) x (5oC/9oF) 37.0 oC

48
Temperature Conversion

• Celsius to Fahrenheit
• ToC x (9oF/5oC) 32 oF T oF
• Example converting 25.0oC to oF
• 25.0 oC x (9oF/5oC) 32 oF 77.0 oF

49
Temperature Conversion

• Celsius to Kelvin T oC 273.15 T K
• Kelvin to Celsius T K 273.15 T oC
• Examples
• 25.0 oC to Kelvin 25.0 273.15 298.2 K
• 310. K to oC 310. 273.15 27 oC

50
Temperature Conversion

• 1) What is the temperature of 65.0 oF expressed
  in degrees Celsius and in Kelvin?
• (Answer 18.3 oC 291.5 K)
• 2) A newly invented thermometer has a T-scale
  that ranges from -50 T to 300 T. On this
  thermometer, the freezing point of water is -20 T
  and its boiling point is 230 T. Find a formula
  that would enable you to convert a T-scale
  temperature to degrees Celsius. What is the
  temperature of 92.5 T in Celsius?
• (Answer 45.0 oC)

51
Density

• Density Mass/Volume
• (Mass Volume x density Volume
  mass/density)
• Units g/mL or g/cm3 (for liquids or solids)
• g/L (for gases)
• SI unit kg/m3
• Examples density of water 1.00 g/mL (1.00
  g/cm3)
• in SI unit 1.00 x 103 kg/m3

52
Determining Volumes

• Rectangular objects V length x width x
  thickness
• Cylindrical objects V pr2l (or pr2h)
• Spherical objects V (4/3)pr3
• Liquid displacement method
• the volume of object submerged in a liquid is
  equal to the volume of liquid displaced by the
  object.

53
Density Determination

• Example-1
• A cylindrical metal rod that is 1.00 m long and
  a diameter of 1.50 cm weighs 477.0 grams. What is
  the density of metal?
• Volume p(1.50 cm)2 x 100. cm 177 cm3
• Density 477.0 g/177 cm3 2.70 g/cm3

54
Density Determination

• Example-2
• A 100-mL graduated cylinder is filled with 35.0
  mL of water. When a 45.0-g sample of zinc pellets
  is poured into the graduate, the water level
  rises to 41.3 mL. Calculate the density of zinc.
• Volume of zinc pellets 41.3 mL 35.0 mL 6.3
  mL
• Density of zinc 45.0 g/6.3 mL 7.1 g/mL (7.1
  g/cm3)

55
Density Calculation 1

• The mass of an empty flask is 64.25 g. When
  filled with water, the combined mass of flask and
  water is 91.75 g. However, when the flask is
  filled with an alcohol sample the combined mass
  is found to be 85.90 g. If we assume that the
  density of water is 1.00 g/mL, what is the
  density of the alcohol sample?
• (Answer 0.787 g/mL)

56
Density Calculation 2

• A 50-mL graduated cylinder weighs 41.30 g when
  empty. When filled with 30.0 mL of water, the
  combined mass is 71.25 g. A piece of metal is
  dropped into the water in the graduate, which
  causes the water level rises to 36.9 mL. The
  combined mass of graduate, water and metal is
  132.65 g. Calculate the densities of water and
  metal.
• (Answer 0.998 g/mL and 8.9 g/mL, respectively)

57
Classification of Matter
58
Classification of Matter

• Mixture matter with variable composition
• Homogeneous mixture
• One that has a uniform appearance and
  composition throughout the mixture
• Heterogeneous mixture
• One that has neither uniform appearance or
  composition the appearance and composition in
  one part of the mixture may differ from the other
  part
• Substance matter with a fixed composition

59
Substances

• Element
• Composed of only one type of atoms it cannot
  be further reduced to simpler forms.
• Compound
• Composed of at least two different types of
  atoms combined chemically in a fixed ratio it
  may be broken down into simpler forms (or reduced
  to the elements)

60
Physical Changes

• Examples
• melting,
• freezing,
• evaporation,
• condensation,
• sublimation,
• dissolution.

61
Chemical Changes

• Examples
• combustion (burning),
• decomposition,
• chemical combination (synthesis),
• fermentation,
• corrosion,
• oxidation and reduction,
• (any chemical reactions)

62
(No Transcript)