chapter 1 introduction to chemistry. chemistry is all around you! chemistry at home: chemistry in...
TRANSCRIPT
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
Weight – the amount of matter in an object and the effect of gravity on that matter
What is the difference between mass and weight?
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.
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
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