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Chemistry• Chemistry – the study of the composition of
substances and the changes that substances undergo.
Branches of Chem.• Organic Chem.
• Inorganic Chem.
• Analytical Chem.
• Physical Chem.
• Biochemistry
• Theoretical
Building Blocks of Matter
• Atom – the smallest unit of an element that maintains the properties of the element
• Element – pure substance made of only one kind of atom
• Compound – substance made from atoms of two or more elements.
Properties of Matter
• Extensive Properties – depends on the amount of matter present (i.e. volume)
• Intensive Properties – Do not depend on the amount of matter present (i.e. boiling point)
Matter• Matter – anything that takes up space and
has mass
• Mass – that amount of matter that an object contains
Changes in Matter• Physical Change –
alteration of a substance without changing it’s composition
• Chemical Change – alteration in the chemical makeup of a substance
States of Matter• Solids – matter that has definite shape and
volume
• Liquids – matter that has definite volume, but takes the shape of its container
• Gas – matter that takes both the shape and the volume of its container
Mixtures• Heterogeneous Mixture
• Homogeneous Mixture
• Solution – a homogeneous mixture
• Phase – any part of a system with uniform composition and properties
Periodic Table• The known elements are organized on the
periodic table.
• Vertical columns are called groups or families
• Horizontal rows are called periods.
Measurements
• Quantitative – Results in a definite forms (usually as numbers)
• Qualitative – Results in a descriptive nonnumeric form
Accuracy and Precision
• Accuracy – How close a measurement comes to the actual true value of what is measured
• Precision – How well a measurement can be reproduced
Significant Figures
• Significant Figures – measurement that includes all digits that can be known accurately plus a last digit that is estimated
Rule One of Significant Figures
• 1) Every nonzero digit in a recorded measurement is significant
• Example: 56.8, 967, 0.735 all have three significant digits
Sig Fig - Rule 2
• Zeros appearing between nonzero digits are significant
• Example: 40005 has 5 Sig Figs
• 5.07 has 3 Sig Figs
• 20.9804 as 6 Sig Figs
Rule 3 – Sig Figs
• Zeros in front of all nonzero digits are not significant
• Example: 0.9837, 0.479, 0.00000084, 0.0000478
Rule 4 – Sig Figs
• Zeros at the end of a number and to the right of a decimal point are significant
• Example: 76.00, 5.080, 4.000
Rule 5 – Sig Figs
• Zeros at the end of a measurement and to the left of a decimal point can be either significant or not depending on how it was measured.
• Example: 300, 2900, 510.• To avoid the unknown, measurements
should be written in scientific notation: 4.90x103.
Sig Figs?
• 145
• 0.274
• 40.308
• 9.700 x 103
• 5.700
• 0.089
• 0.0707
• 76.00
Metric System• Metric System – the standard of
measurement used by scientists
• Established in 1790, the International System of Units (SI units)
SI Units• Length• Meter (m)• Volume• Cubic meter (m3) • Mass• Kilogram (kg)• Temperature• kelvin (K)
• Time• Seconds (s)• Pressure• Pascals (pa)• Energy• Joule (J)
Length• Meter – the distance that light travels in a
vacuum in 1/299,792,458th of a second.
Volume
• Liter – volume of a cube that is 10 m on each edge.
• 10 cm x 10 cm x 10 cm =1000 cm3 = 1 L
Mass• 1 kilogram is defined by a weight in France
roughly equal to the mass of 1 L of water at 40C.
Density• Density – the ratio of the mass of an object
to its volume
• Density = Mass / Volume
• Density is a derived unit because it is a combination of SI base units
Problem Solving
• Problem is a necessary part of chemistry and can only be mastered by practice.
Techniques for Problem Solving
• Identify the unknown• Identify what is given• Plan the solution• Do the calculations• Check your work
Sample Problem
• How many dimes is the equivalent to 10 quarters?
Conversion Factors
• Conversion Factors are ratios of equivalent measurements
• 1 foot = 12 inches
• 1 foot / 12 inches = 1
• 2.54 cm = 1 inch
• 1 inch / 2.54 cm = 1
Dimensional Analysis
• Dimensional Analysis – when units that are part of a measurement are used to solve a problem
• Usually this involves the use of conversion factors
Sample
• A recipe for cookies requires: 3 eggs, 2 cups flour, 1 cup sugar to make 3 dozen cookies
• If you wanted to make enough cookies for exactly 144 people, how many cups of flour do you need?
• How many eggs do you need for 12 people?
Converting Between Units
• 3000 mm in meters
• 0.000005 kK in dK• 5 x 1010 ns in das.
Multistep Problems
• How many seconds in one year?
• How many milligrams of water in 0.45 liters?