Chapter 1 Introduction to Chemistry. Chemistry is all around you! Chemistry at home: Chemistry in the classroom:

Chapter 1

Introduction to Chemistry

Chemistry is all around you!

Chemistry at home:

Chemistry in the classroom:

1.1 A Story of 2 Substances

Chemistry – the study of matter and the changes it undergoes. Matter:

The Ozone Layer

Ozone chemical formula: Substance in the atmosphere that

absorbs harmful UV radiation before it reaches the Earth’s surface Substance

Aka – Matter that has a definite and uniform

composition

Ozone formation: UV radiation breaks oxygen

molecules apart Individual oxygens react with

oxygen molecules to form ozone

Levels of ozone can be measured by balloons, satellites, and rockets.

1980s – scientists realized ozone layer getting thinner

Chlorofluorocarbons

Made of chlorine, fluorine, and carbon Developed in 1928 as refrigerator coolant Also used in air-conditioners, plastic

foams, and as propellants in spray cans

Scientists began to measure CFC levels in 1970s

By 1990 concentrations had reached all time high

Is there a connection between depleting ozone layer and the increase in CFCs?

1.2 Chemistry and Matter

Everything around you is matter Chemists study matter Conclusion:

Matter and its Characteristics

Matter =

Mass – amount of matter in an object

Weight – the amount of matter in an object and the effect of gravity on that matter

What is the difference between mass and weight?

What happens to your weight if you go to the moon?

What happens to your mass if you go to the moon?

Much of matter and its behavior is macroscopic Macroscopic -

The structure, composition, and behavior of all matter can be described on a submicroscopic (atomic) level

Models are used to observe data that is submicroscopic Model – visual, verbal, or mathematical

explanation of experimental data

1.3 Scientific Methods

Scientists use scientific methods to systematically pose and test solutions to questions and assess the results of the tests

A Systematic Approach

Scientific method – a systematic approach used in scientific study. Organized process used by scientists to

do research Provides method for scientists to verify

work of others Steps repeated until hypothesis is

supported or discarded

Observation

Scientific study usually begins with simple observations

Types of observation: Qualitative – how something looks,

feels, sounds, tastes, smells Ex:

Quantitative – uses numbers Ex:

Hypothesis

Tentative explanation for what has been observed

Ex: CFCs break down due to interactions with UV light from the sun & Cl released breaks down ozone

Experiments

Set of controlled observations that test the hypothesis

Must be set up carefully in order to change and test only one variable at a time

Parts of an experiment

You want to test the hypothesis that a beaker of water under a lamp will evaporate faster than a beaker of water on the counter. You add 50 mL of water to 2 beakers and place one on the counter and one under a lamp. You measure the amount of water in each beaker every 30 minutes.

Independent variable – the thing the scientist is testing the effect of (changes)

Dependent variable – the thing the scientist measures Dependent on the independent variable

Constant – factor that is not allowed to change during the experiment

Control – standard for comparison, does not receive the independent variable

Conclusion

Judgment based on the information obtained

Hypothesis can never be proven or disproved, only supported or not supported

Scientists gathered data and developed models that supported the hypothesis that Cl released by CFCs reacts with ozone and depletes it.

Theory and Scientific Law

Theory – explanation of a natural phenomenon based on many observations and investigations over time Broad principle of nature that has been

supported over time Can be modified Atomic theory

Scientific Law – relationship in nature that is supported by many experiments Gravity

1.4 Scientific Research

Scientific investigations result in the development of technology that can improve our lives and the world around us.

Types of Scientific Investigations

Pure research – conducted to gain knowledge for the sake of knowledge itself

Applied research – research done to solve specific problems

Chance discoveries – occur when scientists obtain results that are far different from what they expected

Penicillin – accidentally discovered when a bacterial sample being studied became contaminated with it

What ever happened to that ozone?

CFCs and ozone concentrations are continuously monitored

Montreal Protocol – 1987, nations agreed to phase out use of CFCs

Ozone hole today

Forms each year over Antarctica during the spring

Scientists use models to predict the ozone will not begin to recover until 2068