Matter and Measurement

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Matter and Measurement

• Prof. G. Matthews

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Scientific Method

• Scientific Method A method of acquiring
  knowledge by testing theories.
• Experiments are performed to form a Hypothesis,
  which if confirmed may lead to a Scientific
  Theory.

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Scientific Method

• Definitions
• Fact A statement that is based on direct
  experience.
• Hypothesis - is a statement that is not obvious
  but is used to explain the facts.
• Theory A model that explains many interrelated
  facts and can be used to make predications about
  natural phenomena.

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Scientific Method

• Screening of biological extracts (1960s)
• One of these extracts was found to exhibit marked
  antitumour activity
• 1967 Wall and Wani, isolated the active compound,
  from the bark of the Pacific yew tree (Taxus
  brevifolia).

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Difference Between Mass and Weight

• The difference between mass and weight
• Mass is defined as the amount of material in an
  object.
• Weight is the force that mass exerts due to
  gravity.

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Uncertainty in Measurement

• Syringes, burettes and pipettes deliver liquids
  with more accuracy than graduated cylinders.
• Volumetric flasks are used to contain specific
  volumes of liquid.

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Uncertainty in Measurement

• Exact number
• Number whose value is known exactly.
• Defined value
• 1000 g 1 kg.
• 1 m 100 cm.
• Counting small numbers of objects.

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Uncertainty in Measurement

• Inexact number
• Number whose value has some uncertainty.
• Numbers obtained by measurement
• Equipment and human error.
• Counting very large number of objects.
• Uncertainties always exist in measured quantities.

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Uncertainty in Measurement

• Precision
• How closely individual measurements agree with
  one another.
• Accuracy
• How closely individual measurements agree with
  the correct value.

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Significant Digits

• Significant Figures
• Only the number of digits that are known with
  certainty are significant.
• On ruler A, each division is 1 cm. On ruler B,
  each division is 1 cm and each subdivision is 0.1
  cm.

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Significant Digits

• The data collected represents the uncertainty
  found in a measurement. Watch C has the least
  uncertainty.

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Significant Digits

• Significant Figures
• Measurements are always given to 1 digit of
  uncertainty beyond the last certain digit
• 2.2405 /- 0.0001g
• 2.2406g or 2.2404g
• The last digit in a measured quantity is assumed
  to be uncertain.

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Significant Digits

• All digits of a measured quantity are called
  significant figures.
• Example
• 3.2 g has two significant figures.
• 2.4907 has 5 significant figures.
• The more significant figures in a measurement,
  the greater the certainty in the measurement.

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Significant Digits

• Rules for Significant Figures
• Non-zero numbers are always significant.
• 2.294g 4 significant figures.
• Zeros between non-zero numbers are always
  significant.
• 1005 kg 4 significant figures.

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Significant Digits

• Zeros before the first non-zero digit are not
  significant.
• 0.0003g 1 significant figures.
• Zeros at the end of the number after a decimal
  place are significant.
• 0.0200g 3 significant figures.
• Zeros at the end of a number before a decimal
  place are ambiguous.
• 10,300 g 3 significant figures.

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Significant Digits

• To overcome this ambiguity convert the number to
  scientific notation
• The number of digits remaining is the number of
  significant figures
• 2.50 x 102 cm has 3 significant figures.
• Web assignment Significant Figures

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Significant Digits

• Exact numbers can be treated as if they have an
  infinite number of significant figures.
• 12 in 1 foot is exact.
• Calculations
• The least certain measurement used in a
  calculation limits the certainty of the
  calculated quantity.
• The final answer for any calculation should be
  reported with only one uncertain digit.

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Rounding off Nonsignificant digits

• Rounding off excess digits
• If the first nonsignificant figure is less than 5
  round down.
• If the first nonsignificant figure is 5 or
  greater round up.
• Round off at the end of the mathematical
  operation.

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Adding and Subtracting Measurements

• Addition and Subtraction
• The result can have no more decimal places than
  the measurement with the fewest number of decimal
  places.
• Multiplication and Division
• The result is reported with the same number of
  significant figures as the measurement with the
  fewest significant figures.

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Exponential Numbers

• When a value is multiplied times itself, the
  process is indicated by a superscript.
• This number is called an exponent.
• positive for all numbers greater than 1.
• negative for all numbers less than 1.

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Exponential Numbers

• Several relevant examples of 10 being raised to
  an exponential power.

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Scientific Notation

• Convert big and small numbers into powers of 10
  by moving the decimal point to the left or to the
  right giving us a coefficient and an exponent.
• The coefficient is always greater than 1 and less
  than 10.
• The exponent is positive for numbers greater than
  0 and negative for numbers less than 0.
• Web Assignment Scientific Notation

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Unit Equations and Unit Factors

• Dimensional Analysis
• Carry the units associated with the calculation
  and manipulate them algebraically.
• To convert from one unit to another, use a
  conversion factor.
• Conversions involving volume
• Need to cube both number and unit

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Unit Equations and Unit Factors

• Using two or more conversion factors
• Use two or more conversion factors to convert
  from one unit to another if the relationship
  between the two units is not defined.
• Conversions involving volume
• Need to cube both number and unit
• Web Assignment Conversion Factors

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Units of Measurement
Web Assignment Metric System
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Units of Measurement

• Temperature
• Determines the direction of the heat flow between
  us and the object.
• Heat flows from a high temperature object to a
  low temperature object.

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Units of Measurement

• Density
• Derived SI unit
• Density Mass/Volume
• Units g/cm3, g/mL, g/L.
• Density is temperature dependent!

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Classification of Matter

• Matter
• Physical material of the universe that has mass
  and occupies space.
• Pure Substances
• Matter that has distinct properties and
  composition that doesnt vary from sample to
  sample i.e. H2O, NaCl.
• Atoms
• Smallest building blocks of matter.

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Classification of Matter

• Element
• Cant be decomposed into simpler substances.
  Contains only one kind of atom. i.e. Ag.
• Symbol derived from English or Latin languages or
  the discoverer.

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Classification of Matter

• Molecules
• Two or more of the same atoms combine together.
• 7 diatomics H2, N2, O2, F2, Cl2, Br2, I2.

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Classification of Matter

• Compound
• Two or more different elements combine together.
  i.e. H2O (Molecular compounds)
• Properties of compounds are different than its
  constituent elements.
• Law of Constant Composition or Law of Definite
  Proportions (Proust)
• The proportions of elements in compounds are the
  same irrespective of how the compound was formed.

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Classification of Matter

• Examples of molecules and compounds.

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Classifications of Matter

• Mixtures
• One or more substances not chemically bonded
  together.
• Each substance retains its own chemical identity.
• Composition of mixtures can vary.

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Classifications of Matter

• Heterogeneous Mixture doesnt have the same
  composition throughout i.e. rocks.
• Homogenous (solutions) Mixtures that are uniform
  throughout i.e. air.
• Separate mixtures into its individual components
  by taking advantage of their properties.

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Properties of Matter

• Physical Properties
• Can be measured without changing the identify and
  composition of the substance.
• Color, odor, density, melting point, boiling
  point, and hardness.
• Chemical Properties
• Describe how a substance may react.

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Properties of Matter

• The products have different chemical and physical
  properties than the reactants.

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Properties of Matter

• Intensive properties
• Dont depend on the amount of the sample.
• Temperature, melting point and density.
• Extensive properties (relate to the amount)
• Depend on the amount of the sample.
• Mass, volume, pressure.

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Properties of Matter

• Physical change
• Substance changes its physical appearance but
  not its composition.
• Any change of state is a physical change.
• i.e. change of state of water.
• Chemical change
• Substance is transformed into a chemically
  different substance.
• Burning of hydrogen in oxygen to form water.

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Classification of Matter

• Properties of States
• Solid molecules held tightly together by
  attractive forces in definite arrangement.
  Molecules can vibrate in place.
• Liquid molecules held together by attractive
  forces, but not so tightly, so that the molecules
  can slide over each other.
• Gas, molecules are weakly attracted to each other.