SLE111 Lecture Notes - Lecture 1: Chemical Reaction, Chemical Formula, Periodic Table
13 May 2018
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Fundamentals of General and Organic Chemistry
Chapter 1: Matter and Measurements
1.1 Chemistry: The Central Science
Physical change: A change that does not affect the chemical makeup of a substance or
object
Chemical change: A change in the chemical makeup of a substance
1.2 States of Matter
- Matter exists in three solid forms:
o Solid: a substance that has a definite volume and shame
o Liquid: A substance that has a definite volume and shape but assumes the
shape of its container
o Gas: A substance that has neither a definite volume nor a definite shape
1.3 Classifications of Matter
Pure substance: a substance that has a uniform chemical composition throughout
Mixture: a blend of two or more substances, each of which retains its chemical identity
Homogenous mixture: a uniform mixture that has the same composition throughout
Heterogeneous mixture: a non-uniform mixture that has regions of different
compositions
Element: a fundamental substance that cannot be broken down chemically into any
simpler substance
Chemical compound: a pure substance that can be broken down into simpler
substances by chemical reaction
Reactant: a starting substance that undergoes change during a chemical reaction
Product: a substance formed as a result of a chemical reaction
Chemical reaction: a process in which the identity and composition of one or more
substances are changed
1.4 Chemical Elements and Symbols
Chemical formula: a notation for a chemical compound using element symbols and
subscripts to show how many atoms of each element are present
o E.g. H2O (water) contains 2 hydrogen atoms combined with 1 oxygen atom
1.5 Elements and the Periodic Table
- The periodic table has information that gives chemists the ability to explain known
chemical behaviour of elements and to preduct new behaviour
- Elements can be divided into three groups:
o Metals: a malleable element, with a lustrous appearance, that is a good
conductor of heat and electricity
▪ 94% of current known elements are metals
▪ Solid at room temperature (except mercury)
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▪ Occur on left side of the periodic table
o Nonmetal: an element that is a poor conductor of electricity and heat
▪ 18 elements are nonmetal
• 11 are gasses at room temperature
• 6 are brittle solids
• 1 is a liquid
▪ Right side of the periodic table
o Metalloid: an element whose properties are intermediate between those of
a metal and nonmetal
▪ 6 elements are metalloids
▪ E.g. Pure silicone has a lustrous or shiny surface, like metal, but is
brittle, like a nonmetal, and its electrical conductivity lies between
that of a metal and nonmetal
▪ Occur in a zigzag band between metals on the left and nonmetals on
the right of the periodic table
1.6 Chemical Reactions: An Example of Chemical Change
- Nickel is a hard, shiny metal
- Hydrogen chloride is a colourless gas that dissolves in water to form hydrochloric
acid
- When nickel is added to hydrochloric acid; the nickel is eaten away; the solution
turns green; a gas bubbles out
- A chemical reaction is taking place. This is indicated by:
o Change in colour
o Dissolving of nickel
o Appearance of bubbles
- Chemical reactions are indicated by:
o Change in temperature
o Change in colour
o Change in physical state
▪ Solid dissolves
▪ Gas (bubbles) formed
1.7 Physical Quantities
Physical quantity: a physical property that can be measured
Unit: a defined quantity used as a standard of measurement
SI units: Units of measurement defined by the International System of Units
o Mass – Kilograms (kg)
o Length – Meters (m)
o Volume – Cubic meters (m3)
o Temperature – Kelvins (K)
o Time – Seconds (s)
o Amount of substance – Mole (mol)
o Electric current – Ampere (A)
o Luminous intensity – Candela (cd)
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1.8 Measuring Mass, Length and Volume
Mass: a measure of the amount of matter in an object
Weight: a measure of the gravitational force that the earth or larger body exerts on an
object
- Mass does not depend on location, if you are on the earth or moon your body mass
is still the same
- Weight does depend on location, your weight on earth may be 64kg, however, on
the moon it may only be 10kg due to less gravity
- The mass of an object can be determined by comparing the weight of the object to
the weight of a known reference standard
1.9 Measurement and Significant Figures
- Every experimental measurement, no matter how precise, has a degree of
uncertainty to it because there is always a limit to the number of digits that can be
determined
Rules for determining significant figures
1. Zeros in the middle of a number are like any other digit; they are always
significant. Thus, 94.072g has five significant figures
2. Zeros at the beginning of a number are NOT significant; they only act to locate
the decimal point. Thus, 0.0834cm has three significant figures, and 0.02907mL
has four
3. Zeros at the end of a number and after the decimal point are significant. It is
assumed that these zeros would not be shown unless they were significant. Thus,
138.200m has six significant figures. If the value were known to only four
significant figures, we would write 138.2m
4. Zeros at the end of a number and before an implied decimal point may or may
not be significant. We cannot tell whether they are a part of the measurement or
whether they act only to locate the unwritten but implied decimal point. Thus
23,000kg may have two, three, four, or five significant figures. Adding decimal
point at the end would indicate all five numbers are significant
1.10 Scientific Notation
- Rather than writing very large or very small numbers entirely, it is more convenient
to express them using scientific notation
Scientific notation: a number expressed as the product of a number between 1 and
10, time the number 10 raised to a power
o e.g. 215 written in scientific notation is 2.15 x 102
▪ 215 = 2.15 x 100 = 2.15(10 x 10) = 2.15 x 102
- Where the number is larger that 1, the decimal point has moved to the left until it
follows the first digit
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Document Summary
Physical change: a change that does not affect the chemical makeup of a substance or object. Chemical change: a change in the chemical makeup of a substance. Pure substance: a substance that has a uniform chemical composition throughout. Mixture: a blend of two or more substances, each of which retains its chemical identity. Homogenous mixture: a uniform mixture that has the same composition throughout. Heterogeneous mixture: a non-uniform mixture that has regions of different compositions. Element: a fundamental substance that cannot be broken down chemically into any simpler substance. Chemical compound: a pure substance that can be broken down into simpler substances by chemical reaction. Reactant: a starting substance that undergoes change during a chemical reaction. Product: a substance formed as a result of a chemical reaction. Chemical reaction: a process in which the identity and composition of one or more substances are changed.
