What is Chemistry

1
What is Chemistry?

• Chemistry is a study of matter and the changes it
  undergoes
• Coal- Burning of coal
• Air- Breathing
• Eggs- Boiling eggs

2
Why study chemistry?

• Chemistry is the scientific study of matter, and
  matter is everywherethink of a field in science-
  biology, physics, geology, ecology all require
  the knowledge of matter

3
What is matter?

• Matter is anything that has mass and occupies
  space.
• Is bread a matter?
• Is air a matter?
• Mass is-a measurement of the amount of matter in
  an object.
• Mass is independent of the location of an object.
• An object on the earth has the same mass as the
  same object on the moon.

4
What are the types of properties?

• Physical properties can be observed or measured
  without attempting to change the composition of
  the matter being observed.
• Examples ?
• Chemical properties can be observed or measured
  only by attempting to change the composition of
  the matter being observed.
• Examples ?

5
What are the types of properties?

• Extensive v/s intensive
• Extensive- depends on how much of matter is being
  considered
• eg- Mass, Volume
• Intensive- is independent of the amount of matter
  being considered
• eg- Density

6
What are the types of properties?

• Macroscopic properties
• That can be observed directly
• Microscopic properties
• That are on the atomic and molecular scale and
  cannot be observed with naked eyes

7
Chemistry- Study of Change

• Physical changes of matter
• Physical changes take place without a change in
  composition.
• Examples of physical changes are the freezing,
  melting or evaporation of a substance such as
  water.

8
Chemistry- Study of Change

• Chemical changes of matter
• Chemical changes are always accompanied by a
  change in composition.
• Examples burning of paper, the fizzing of a
  mixture of vinegar and baking soda.

9
Chemistry- Study of Atoms and Molecules

• A molecule is the smallest particle of a pure
  substance that is capable of a stable independent
  existence.
• An atom is the smallest unit of an element that
  can exist as a stable, independent entity. Atoms
  make up molecules.
• Diatomic molecules contain two atoms.
• Triatomic molecules contain three atoms.
• Polyatomic molecules contain more than three
  atoms.
• Homoatomic molecules contain atoms of the same
  kind.
• The atoms contained in heteroatomic molecules are
  of two or more kinds.

10
Chemistry- Study of Atoms and Molecules

• Oxygen gas-
• Homoatomic
• Diatomic

Carbon monoxide- Heteroatomic Diatomic
Carbon dioxide- Heteroatomic Triatomic
11
Classification of Matter

• Mixtures can be further classified
• Homogeneous Mixture- Uniform appearance and same
  properties throughout
• Heterogeneous Mixture- Properties and appearance
  non-uniform throughout
• Exercise 1.22

12
Classification of Matter

• Examples-
• Elements
• Compounds
• Exercise- 1.18

13
Measurements and Units

• Why do we need measurements?
• Measurements consist of-
• a number
• a unit or label (feet, pounds or gallons)
• Examples ??
• The metric system is a decimal system in which
  larger and smaller units are related by factors
  of 10.

14
SI Units

• 7 Base quantities and units (SI-International
  System of Units)

And then there are n number of derived units of
measurements. Multiplication/Division of one or
more base units
15
Common prefixes of metric system
16
Length related commonly used Derived Units

• Area- (Length) (Length)
• Volume- (Length) (Length) (Length)

Temperature Scale
Fahrenheit ? 32 F freezing, 212F Water
boiling Kelvin (Also called the absolute
scale) Celsius ? 0C freezing, 100C Water
boiling Rankine (Not common)
17
Temperature Scale
18
Conversion of Temperature scales

• Converting Fahrenheit to Celsius
• C 5/9 (F 32)
• Converting Celsius to Fahrenheit
• F 9/5 (C ) 32
• Converting Kelvin to Celsius
• C K 273
• Converting Celsius to Kelvin
• K C 273
• Example 1.7
• Exercise 1.43

19
The Process of Lying or the Art of Numbers!
April 3rd 2007
April 5th 2007
http//dilbert.com/
20
More numbers- Scientific notation

• 0.000000000005
• Scientific Notation
• Product of two parts in the form M x 10n
• - M is a number between 1 and 10 (but not equal
  to 10)
• - n is a ve or ve whole number (power of 10)
• 0.000000000005 becomes
• M written with the decimal in the standard
  position
• The standard position for the decimal is to the
  right of the first nonzero digit in the number M
• 0.005 becomes 5.0 10-3

5.0 10-12
21
More numbers- Scientific notation

• Significance of the exponent n
• A positive n value indicates the number of places
  to the right of the standard position that the
  original decimal position is located.
• A negative n value indicates the number of places
  to the left of the standard position that the
  original decimal position is located.
• Learning check 1.10

22
Scientific notation operations

• Addition and subtraction
• same power of 10 (n), conventional operation with
  M
• Multiplication and division
• conventional operation with M, powers (n) added
  in multiplication, subtracted in division
  operations
• Example 1.11

23
Numbers- Significant figures

• Measurements are limited by the device in use.
• Significant Figures
• Significant figures are the numbers in a
  measurement that represent the certainty of the
  measurement, plus one number representing an
  estimate.
• 1.5 cm ? Significant figures 2
• 0.015 m ? Significant figures still 2
• 1.50 cm ? Significant figures 3
• Leading zeros are never significant figures.
• Buried and trailing zeros are always significant
  figures.
• Learning check 1.13

24
Operations with Significant Figures

• Addition, subtraction
• Number of digits retained to the right of decimal
  place in the number in the calculation with the
  fewest such digits
• Multiplication, division
• Number of sig. fig. in final answer the number
  in calculation with the fewest sig. fig.
• Rounding off (digit to be dropped off)- equal to
  or greater than 5

25
Dimensional Analysis (Factor-Unit method)

• Step 1 Write down the known or given
  quantity.Include both the numerical value and
  units of the quantity.
• Step 2 Leave some working space and set the
  known quantity equal to the units of the unknown
  quantity.
• Step 3 Multiply the known quantity by one or
  more factors such that the units of the factor
  cancel the units of the known quantity and
  generate the units of the unknown quantity.
• Step 4 After you generate the desired units of
  the unknown quantity, do the necessary arithmetic
  to produce the final numerical answer.

26
Dimensional Analysis (Factor-Unit method)

• Step 1 Write down the known or given
  quantity.Include both the numerical value and
  units of the quantity.
• 2.54 m (Numerical Value 2.54 Units meters)
• Step 2 Leave some working space and set the
  known quantity equal to the units of the unknown
  quantity.
• 2.54 m --- cm

27
Dimensional Analysis (Factor-Unit method)

• Step 3 Multiply the known quantity by one or
  more factors such that the units of the factor
  cancel the units of the known quantity and
  generate the units of the unknown quantity.
• 2.54 m --- cm
• Step 4 After you generate the desired units of
  the unknown quantity, do the necessary arithmetic
  to produce the final numerical answer.
• 254 cm

28
Density

• Density is the ratio of the mass of a sample of
  matter divided by the volume of the same sample.
• or
• Density calculation involves knowledge of
• Mass and b) Volume
• Example 1.20

29
Density

• A 20.00 mL sample of liquid is put into an empty
  beaker that had a mass of 31.447 g. The beaker
  and contained liquid were weighed and had a mass
  of 55.891 g. Calculate the density of the liquid
  in g/mL.
• Mass of the liquid Mass of the beaker with
  contained liquid Mass of the empty beaker