Chapter 1

Why study chemistry?◦ Chemistry – the study of matter and the changes

it undergoes.◦ Why is this important to me?

Two real-life events involving two discoveries can help answer this question. The refrigerator Energy from the sun

The Ozone Layer◦ Sunburns result from the ultraviolet (UV) radiation

from the sun.◦ Overexposure to UV radiation is harmful to plants

and animals. UVB can cause cataracts and skin cancer in humans UVB can cause lower crop yields in agriculture UVB can cause disruption in food chains in nature

Earth’s Atmosphere◦ Living organisms on Earth exist due to protection

from high levels of UVB◦ What offers this protection?

Ozone Ozone is made up of oxygen, O3

Ozone is a substance in the atmosphere that absorbs most harmful radiation before it reaches the Earth’s surface

Earth’s Atmosphere◦ Substance- also known as a chemical, is matter

that has definite and uniform composition◦ About 90% of Earth’s ozone is spread out in a

layer that surrounds and protects our planet.◦ Ozone layer is located in the stratosphere

Ozone Formation◦ How does ozone enter the stratosphere?

When oxygen gas (O2) is exposed to UV radiation in the upper regions of the stratosphere, ozone (O3) is formed

Energy from UV radiation breaks O2into individual oxygen particles (O), which then interact with O2 to form O3

Chlorofluorocarbons (CFCs)◦ Is a substance that consists of chlorine, fluorine,

and carbon◦ Several different substances are classified as

CFCs◦ CFCs are nontoxic and stable—do not readily

react with other substances◦ By 1935, they seemed ideal for coolants in

refrigerators and propellants in spray cans

Chlorofluorocarbons (CFCs)◦ 1970s

Scientists began detecting CFCs in the atmosphere After measuring the amount of CFCs in the

stratosphere, it was evident the amount increased yearly

Consequently the ozone layer was thinning

Chemistry and Matter

Matter and its characteristics◦ Matter, the stuff of the universe, has many

different forms.◦ Some occurs naturally, such as ozone◦ Some do not occur naturally, such as CFCs◦ Mass – is a measurement that reflects the amount

of matter

Mass and weight◦ Weight – the measurement not only of the

amount of matter but also of the effect of the Earth’s gravitational pull on that matter

Structure and observable characteristics◦ What can you observe about the outside of our

school building?◦ What can’t you see from the outside?◦ What about when you bend your arm?◦ Macroscopic – visible to the naked eye; no need

for a microscope◦ Submicroscopic – too small to be seen through a

microscope Atoms are so small they are submicroscopic

Structure and observable characteristics◦ Chemistry seeks to explain submicroscopic events

that lead to macroscopic observations.◦ Scientists use models

Model – is a visual, verbal, or mathematical explanation of experimental data

Chemistry: The central science◦ A basic understanding of chemistry is central to

all sciences—biology, physics, Earth science, ecology and more

◦ Chemistry is broken down into different branches that focus on specific areas

Chemistry: The central science◦ Organic chemistry ◦ Inorganic chemistry◦ Physical chemistry◦ Analytical chemistry◦ Biochemistry◦ Environmental chemistry◦ Industrial chemistry◦ Polymer chemistry◦ Theoretical chemistry◦ Thermochemistry

Scientific Methods

One day, you come home from the movies and find it’s dark inside your house. You flip the light switch and nothing happens. What do you do? What could have happened to the light?

A systematic approach◦ Scientific method – is a systematic approach used

in scientific study, whether it is chemistry, biology, physics, or another science.

Observation◦ Observation is the simple act of gathering

information.◦ The first type of observation is qualitative data

Qualitative data – information that describes color, odor, shape, or some other physical characteristic.

Anything that relates to the five senses is qualitative◦ Another type of data is quantitative data

Quantitative data – this is numerical information

Hypothesis◦ Hypothesis – is a tentative explanation for what

has been observed◦ There is no formal evidence to support a

hypothesis when it is made◦ A hypothesis is meaningless without data to

support it.

Experiments◦ Forming a hypothesis helps the scientist focus on

the next step—experiment.◦ Experiment – is a set of controlled observations

that test the hypothesis.◦ Independent variable – the variable that you plan

to change◦ Dependent variable – its value changes in

response to a change in the independent variable

Other factors◦ Constant factors are not allowed to change

throughout the experiment◦ Control – a standard for comparison

Controlling variables◦ Sometimes it is easier to simulate conditions in a

laboratory, where variables can be controlled.◦ Interactions between CFCs and ozone, are harder

to study in the stratosphere with so many variables

Conclusion◦ Conclusion – is a judgment based on the

information obtained◦ A hypothesis can never be proven◦ Data can support the hypothesis, which can

indicate that the hypothesis may be true◦ If further evidence does not support the

hypothesis it must be discarded or modified◦ Majority of hypotheses are not supported, but can

yield helpful information

Theory and Scientific Law◦ Theory – is an explanation of natural phenomenon

based on many observations and investigations over time Einstein’s theory of relativity Atomic theory

◦ Scientific Law – a relationship in nature that is supported by may experiments Newton’s laws

Scientific Research

Types of Scientific Investigations◦ Pure research – to gain knowledge for the sake of

knowledge itself◦ Applied research – is research undertaken to

solve a specific problem

Chance discoveries◦ Alexander Flemming

Penicillin ◦ Julian Hill

Nylon

Students in the Laboratory◦ Write down ten rules that you believe would be

found within a laboratory environment.

The Story Continues◦ The Montreal Protocol

In 1987, Montreal Protocol was signed Worked to phase out the global use of CFCs

◦ The ozone hole today Models show it will begin to recover

The benefits of chemistry◦ Involved in

Finding cures or vaccines for diseases such as AIDS and influenza

Cars Lasers Plastics Technology And much more