Chemistry for Changing Times 10th edition
Hill/Kolb
Chapter 1
Chemistry: A Science for All
Seasons
• Involved
in everything
What Is Chemistry?
• Study of matter and the changes matter
undergoes
• Matter – anything having mass
Mass and Weight
• Mass: measure of the quantity of matter in
an object
• Weight: measures the gravitational force
between two objects
– Weight varies with strength of gravitational
force
Conceptual Example 1.2 Mass and Weight
Example: On the planet Mercury gravity is 0.376 times that on Earth.
(a) What would be the mass on Mercury of a person who has a mass of
62.5 kilograms (kg) on Earth? (b) What would be the weight on Mercury
of a person who weighs 124 pounds (lb) on Earth?
Example: At the surface of Venus, the force of gravity is
only 0.903 times that on Earth’s surface. (a) What would be
the mass of a standard 1.00-kg object on Venus? (b) A man
who weighs 198 lb on Earth would weigh how much on the
surface of Venus?
Physical Properties
• Physical characteristics and behavior of
a substance
Chemical Properties
• Describe how a substance reacts with
other types of matter
Physical Change
• No change in type or arrangement of
atoms in the substance
• Examples
– Ice melts to liquid water
– Sugar dissolves in coffee
Chemical Change
• Change of type and/or arrangement of
atoms
• Examples
– Iron and air produce rust
– Hydrogen and oxygen produce water
Conceptual Example 1.3 Chemical Change and Physical Change
Example: Which of the following events involve chemical
changes and which involve physical changes?
a. You trim your fingernails.
b. Lemon juice converts milk to curds and whey.
c. Water boils.
d. Water is broken down into hydrogen gas and oxygen gas.
Exercise 1.3A
Which of the following events involve chemical
changes and which involve physical changes?
a. Liquid alcohol vaporizes from an open container.
b. A piece of lithium metal burns in air to form a
white powder called lithium oxide.
c. A dull saw is sharpened with a file.
States of Matter
Substances and Mixtures
• Substances have definite fixed
compositions that do not vary from
sample to sample
• Mixtures have composition that varies
from sample to sample
Relationship Between Substances
and Mixtures
Elements
• An element is one of the fundamental
substances from which all things are
constructed
– Cannot be broken into smaller things
• 114 elements known
– Not all found in nature
Chemical Symbols
• Usually one or two letters from name of
element …
Name
Symbol
Beryllium
Be
Carbon
C
Copper
Cu
(from Latin, cuprum)
Potassium
K
(from Latin, kalium)
Compounds
• Made of two or more elements
chemically combined
• Subscript indicates how much of each
element is present
Water – H2O
Alcohol – CH3CH2OH
Methane – CH4
Conceptual Example 1.4 Elements and Compounds
Example: Which of the following represent elements and which
represent compounds?
H
Hg
HI
BN
In
HBr
Exercise 1.4
Which of the following represent elements and which represent
compounds?
He
CuO
No
NO
KI
Os
Atoms and Molecules
• Atoms are the smallest characteristic
part of an element
• Molecules are the smallest characteristic
part of most compounds
– Group of atoms bound to each other
Measurement
• Scientists use International System of
Units (SI system)
Exponential Numbers
• Method to work with very small or very
large numbers
– Atom has a diameter of 0.0000000001 m
or 1 x 10–10 m
– Sun has diameter of 1,400,000,000 m or
1.4 x 109 m
Exponential Numbers in SI System
Example 1.5 Converting Powers of Ten to Prefixes
Example: Convert each of the following measurements to
a unit that replaces the power of 10 by a prefix.
a. 2.89 x 10–3 g
b. 4.30 x 103 m
Exercise 1.5
Convert each of the following measurements to a unit that
replaces the power of 10 by a prefix.
a. 7.24 x 103 g
b. 4.29 x 10–6 m
c. 7.91 x 10–3 s
Density (d)
• Quantity of mass (m) per unit volume (V)
OR
d = m/V
• Lower density objects float on higher density objects
– Objects less dense than water
• Ice, wood
– Objects more dense than water
• Copper, gold, lead
• Means to determine density
Example: What is the density of iron if 156 g of iron
occupies a volume of 20.0 cm3?
Exercise 1.8A
What is the density, in grams per milliliter, of a salt
solution if 55.0 mL has a mass of 60.5 g?
Exercise 1.8B
What is the density, in grams per cubic centimeter,
of a metal alloy if a cube that measures 2.00 cm on
an edge has a mass of 94.7 g?
Energy
• Required to make something happen that
otherwise would not
• Typically accompanies physical or chemical
changes
• Released during some chemical reactions
Heat
• Heat is energy that flows from a warmer
object to a cooler one
– Units of calorie, Calorie, or joule
1 calorie = 4.184 J
1 Calorie = 1000 calories
– Which sounds better, a donut with 600 Calories or
600,000 calories?
Temperature
• Temperature measures how hot or cold
an object is
Example: Ether boils at 36°C. What is the boiling
point of ether on the Kelvin scale?
Exercise 1.11A
How is the boiling point of water (100°C)
expressed in kelvins?
Exercise 1.11B
Express a temperature of –78°C in kelvins.
Scientific Research
• Applied research: trying to solve a
particular problem in industry or
environment
• Basic research: searching for
knowledge for its own sake
Risks and Benefits
Benefits – promote well-being or have a
positive effect
Risks – hazards that lead to loss or injury
Desirability Quotient = Benefits
Risks