Objectives:  Define and describe chemistry.  Differentiate among traditional branches of chemistry.  List reasons to study chemistry and how it affects your daily life.  Describe the steps involved in the scientific method.  Distinguish between a theory and scientific law.

I. What is Chemistry? a. Chemistry is: The study of matter and the changes that matter undergoes, along with accompanying energy changes.

I. What is Chemistry? b. Traditional Branches of Chemistry: 1.Organic Chemistry – the study of essentially all substances containing the element carbon. 2.Inorganic Chemistry – studies substances that do not contain the element carbon. 3.Analytical Chemistry – deals with the composition of substances. 4.Physical Chemistry – deals with the behavior and motion of chemicals. 5.Biochemistry – the study of chemistry of living organisms.

II. The Scientific Method ObservationHypothesisExperimentConclusion A logical approach to the solution of a scientific problem.

II. The Scientific Method a.Observation – use senses and tools to obtain information directly. 1. Qualitative Data – deals with descriptions (EX: white boards, blue liquid, bubbles, soft, smooth, etc.) 2. Quantitative Data – deals with numbers (EX: 12 books, 1.3 lbs, 100 meters)

Example 1: For each of the following statements, write “L” for qualitative and “N” for quantitative. _____1. The box is brown. _____2. The box is 12 cm long. _____3. The box is empty. _____4. The box has red words written on the side. _____5. The box is 8 cm wide. _____6. The box has a bumpy interior. _____7. The box has a lid. _____8. The box is 4 cm tall.

II. Scientific Method b. Hypothesis – proposed explanation or reason for what is observed. A good hypothesis: 1. Explains an observation 2. Can be tested 3. Will predict an outcome

Example 2: If__________________, then __________________. Write a hypothesis for each question: 1. Does the amount of sunlight a tomato plant receives affect the size of the tomatoes? 2. Plants grow best when watered with spring water.

II. The Scientific Method c. Experiments – means to test a hypothesis through data collection and analysis. An experiment: 1. Should be designed to test a hypothesis 2. Performed under controlled conditions (change one thing, measure one thing) 3. Involves variables

A student decides to set up an experiment to see if detergent affects the growth of seeds. He sets up 10 seed pots. 5 of the seed pots will receive a small amount of detergent in the soil and will be placed in the sun. The other 5 seed pots will not receive detergent and will be placed in the shade. All 10 seed pots will receive the same amount of water, the same number of seeds, and the same type of seeds. He grows the seeds for two months and charts the growth every 2 days. What is wrong with his experiment? Example 3

Variables: 1. Variables: Factors that can be changed. a. Independent –manipulated variable; changed by the scientist I. Control Group – used for comparison; does not receive change b. Dependent – changes as a result of the experiment c. Control: all other variables that are held constant (they do not change)

Example 4: 1. List three variables that would affect the attendance at a football game.

Example 4 cont. 2. A student has a wagon of a certain mass. He plans to investigate how the acceleration of the wagon changes as the force he exerts on it increases. In his investigation, the independent variable is— A. The acceleration of the wagon B. The force acting on the wagon C. The mass of the wagon D. The mass of the student.

3. A student wants to conduct an experiment to find out how pulse rates changes as the length of time spent exercising increases. The dependent variable will be _____. A. breathing rate B. pulse rate C. time spent exercising D. the kind of exercise Example 4 cont.

4. A student hypothesized that the amount of sunlight a sunflower plant receives determines the number of sunflower seeds the plant produces. In her experiment, the number of seeds produces is the _____. A. dependent variable B. independent variable C. controlled variable D. manipulated variable Example 4 cont.

5. A student is planning an experiment to find out how the height from which he drops a ball affects how high the ball bounces. The dependent variable is the ____. A. diameter of the ball B. force acting on the ball C. height that the ball bounces D. height from which the ball is dropped Example 4 cont.

6. If the sugar amount increases then the candy bar will taste sweeter. _____________________ is the independent variable _____________________ is the dependent variable. Example 4 cont.

7. Does the amount of sunlight a tomato plant receives affect the size of the tomatoes? Refer to your hypothesis from Example 1 Independent Variable: Dependent Variable: Control Variables:

Example 4 cont. 8. Plants grow best when watered with spring water. Refer to your hypothesis from Example 1 Independent Variable: Dependent Variable: Control Variables:

II. The Scientific Method d. Conclusion – statement made about experimental results, related to the hypothesis 1. Theory – An explanation of why experiments give certain results. It can never be proven because it is always possible a new experiment will disprove it. EX: Theory of evolution. 2. Scientific Law – Summarizes the results of many experiments. Used to describe, not explain a concept. EX: Newton’s Law of Gravity (Could predict, not explain)