Chemistry Adapted from Stephen L. Cotton Scientific Method Chemistry Adapted from Stephen L. Cotton

The Scientific Method A logical approach to solving problems or answering questions. Starts with observation- noting and recording information and facts and then a hypothesis is proposed- an explanation for the observation; it must be tested by an experiment.

Steps in the Scientific Method 1. Observation (uses your senses) a) quantitative involves numbers = 95oF b) qualitative is word description = hot 2. Hypothesis (ideas-why) - possible explanation for the observation, or “educated” guess 3. Expermiment (the test) - gathers new information to help decide whether the hypothesis is valid

Controlled Experiment- -Must have a “controlled” experiment- designed to test the hypothesis only -can only test one “factor” at a time, that way results compared to the control can only be from what was changed not anything else

We deal with variables, or factors that can change. Two types: A) Manipulated variable (or independent variable) is the one that we change B) Responding variable (or dependent variable) is the one observed during the experiment For results to be accepted, the experiment needs to always produce the same result

only two possible answers: hypothesis is right 4. Record and Analyze Data (the stuff) - record data in data tables and create graphs 5. Conclusion (so…) - draw a conclusion based on the evidence presented by the data only two possible answers: hypothesis is right hypothesis is wrong-start over with a new hypothesis

- Page 22 Using your senses to obtain information The procedure that is used to test the hypothesis Hypothesis is a proposed explanation; should be based on previous knowledge; an “educated” guess Tells what happened A well-tested explanation for the observations; cannot be proven due to new discoveries

Law vs. Theory A law summarizes what has happened. A theory (or model) is an attempt to explain why it happened – this changes as new information is gathered.

- Page 16 Let’s examine some information from a graph. 88.2% 440,000 After lead was banned in gasoline, paint, and public water supply systems, less lead entered the environment.