branches of chemistry scientific method experimental design
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Introduction to Chemistry
Branches of ChemistryScientific Method
Experimental Design
Q: Why are chemists great at solving problems?
A: They have all the solutions!!!
Chemistry Joke
Organic◦ Associated with CARBON compounds.
Inorganic◦ Associated with NON-CARBON compounds.
Analytical◦ Associated with the COMPOSITION of samples
Physical◦ Associated with the BEHAVIOR/ENERGY of
compounds Biochemical
◦ Associated with the chemistry of LIFE
Branches of Chemistry
A logical, systematic approach to the solution of a scientific problem.
Steps in the scientific method include:1.Making observations2.Formulating hypotheses 3.Testing hypothesis through
experimentation4.Developing theories or
formulating laws.
The Scientific Method1.3
1. Making Observations
◦When you use your senses to obtain information, you make an observation.
The Scientific Method1.3
2. Formulating Hypotheses
– A hypothesis is a proposed explanation for an observation.
3. Testing Hypotheses through Experimentation
The Scientific Method1.3
An experiment is a procedure that is used to test a hypothesis.
The experimental design is critical to the reliability of the results.
We should have only one manipulated variable and one dependent variable.
◦We want to test the effect of the manipulated variable on the dependent variable.
◦For example: The effect of surface area on solubility The effect of temperature on pressure
Experimental Design
Experimental DesignD
RY
MIX
Dependent Variable
Relies on the Other
Y-axis
Manipulated Variable
Independent
X-axis
We often graph our results.
The manipulated variable will be on the x-axis.The dependent variable will be on the y-axis.
Our results can show a direct relationship or an indirect/inverse relationship.
Experimental Design
DIRECT (X/Y)
INDIRECT (XY)
We should be careful to change only one variable.
◦For example, use the same equipment for each trial.
◦Conduct each trial under the same conditions.
Experimental Design
We should have a control.◦ This is a trial in which the manipulated variable
is not changed—used for comparison. We should average the results of many
trials.◦ To find the mean, add the results of each trial
and divide by the total number of trials. ◦ More trials produce better reliability of results.
Results should be reproducible by other scientists.
We should report all results, not just the expected ones.
Experimental Design
Chemists often use probeware to measure such things as pH, temperature, or pressure.◦ The probes connect to a computer and
the data is graphed automatically.
Experimental Design
Computer simulations are also often used to test theories.
4. Developing Theories Once a hypothesis meets the test of
repeated experimentation, it may become a theory.
A theory is a loooong explanation for WHY something happens.
A theory may need to be changed at some point in the future to explain new observations or experimental results.
The Scientific Method1.3
4. Formulating Scientific Laws
A scientific law is a short mathematical statement of WHAT happens.
A scientific law doesn’t try to explain the relationship it describes. That explanation requires a theory.
The Scientific Method1.3
Steps in the Scientific Method
Chemistry Joke
Q: What substance has the formula HIJKLMNO?
A: Water (H to O)!!!
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