Welcome to the World of Chemistry

Objectives 1. Analyze the components of a properly designed scientific investigation 2. Evaluate the accuracy and precision of data

Chemistry Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter.

The Scientific Method Definition: Steps: A logical, stepwise approach used by scientists to find answers to questions. Steps: 1. Observation: Observations are made by scientists about their surrounding environment. The observations enable the scientists to illicit questions. 2. State the Problem: The problem statement is in the form of a question. It is derived from the observations made by the scientist. It must be measureable.

3. Conduct Background Research: Information about the problem must be researched by the scientist. This is accomplished by research journals and periodicals, textbooks, internet databases, consultation with professors, etc. Form a Hypothesis: A hypothesis (an educated guess) is formed and stated based upon the background information acquired by the scientist. Example – If I give my plants fertilizer in the spring, they will have more flowers.

State a testable hypothesis The Acme Cleansers Company wants to do some advertising for its new anti-bacterial kitchen cleaner. The advertising executives want to run some tests that show that their new product is better than the current best-selling brand of kitchen cleaner. Mrs. Averett’s Advanced Topics class is in charge of filling the bird feeders at Central Park. You notice that the nuthatches seem to prefer to eat at the sunflower seed feeder more than they eat at the mixed seed feeder.

Design and Perform an Experiment: It is essential for the scientist to gather a list of materials and methods before the experimentation begins. In addition, it is essential that the experimenter designs the experiment in such a way that it is reproducible. A proper experiment compares two or more things but changes only one variable or factor in the experiment. Many experiments will have two groups Experimental group – The group in an experiment that receives the variable being tested. The control group – The group that does not receive the test variable Types of variables Independent variable – The variable that is purposely changed Dependent variable – The variable that is measured Controlled variable – The variable that remains constant

Researchers want to know if the gas mileage of cars will increase with a new type of asphalt surface on roads. What is the independent variable? A. Gas mileage of cars B. Type of car C. Type of asphalt

People with an income greater than $50,00 spend more money on eating out than people who make less than $30,00 What is the independent variable? A. Amount of money earned B. Money spent of eating out C. Type of restaurant

Covering a scrape with a band-aid decreases healing time What is the dependent variable? A. Type of band-aid B. Covering a scrape C. Healing time

Athletes who do not get enough sleep the night before will not run as fast the next day. What is the control group? A. Athletes who do not get enough sleep B. Athletes who get a good night’s rest C. The type of race

The 3N Chemical Company has developed a new termite prevention treatment for wood. The researchers want to find out if it is more effective than the leading brand on the market. What is the experimental group? A. The 3N Chemical Company B. The wood treated with the new termite prevention C. The wood treated with the leading brand of termite prevention

A group of college students were given a short course in speed-reading A group of college students were given a short course in speed-reading. The instructor was curious if a monetary incentive would influence performance on a reading test taken at the end of the course. Half the students were offered $5 for obtaining a certain level of performance on the test, the other half were not offered money. Identify the Independent variable Dependent variable Experimental group Control group

6. Gather, Organize, and Analyze Data: Data (information from the experiment) whether qualitative or quantitative must be accurately recorded. The data can be properly displayed in a graph, chart, table, etc. Data should be accurate and precise.

Accuracy & Precision Accuracy: Precision: How close you are to the actual value Depends on the person measuring Precision: How finely tuned your measurements are or how close they can be to each other Depends on the measuring tool

Accuracy & Precision may be demonstrated by shooting at a target. Accuracy is represented by hitting the bulls eye (the accepted value) Precision is represented by a tight grouping of shots (they are finely tuned)

Accurate but not Precise Accurate & Precise Accurate but not Precise Precise but not accurate Not precise or accurate

Accuracy vs. Precision Susan conducts an experiment five times and gets a solution concentration of 1.9M, 2.1M, 1.8M, 1.9M, and 2.2M. The known concentration of the solution is 2.0M. Which of the following is true about Susan’s results? A. They are accurate, but not precise B. They are precise, but not accurate C. They are neither accurate nor precise D. They are both accurate and precise

Accuracy vs. Precision Martin is conducting an experiment. His first test gives him a yield of 5.2 grams. His second test gives him a yield of 1.3 grams. His third test gives him a yield of 8.5 grams. On average, his yield is 5.0 grams, which is close to the known yield of 5.1 grams of substance. Which of the following are true? A. They are accurate, but not precise B. They are precise, but not accurate C. They are neither accurate nor precise D. They are both accurate and precise

Accuracy vs. Precision Jared is practicing for a golf tournament. His normal driver distance is 250 yards. He hits three balls with his driver, and they travel a distance of 190 yards, 195 yards, and 193 yards. Which of the following is true? A. They are accurate, but not precise B. They are precise, but not accurate C. They are neither accurate nor precise D. They are both accurate and precise

Form a Conclusion: Based upon the experimental results, conclusions can be made regarding the study. These conclusions should support or reject the hypothesis but never prove or disprove.

How are these concepts related to each other? Theories Hypotheses Laws

When proven that it always works L A W (fact) When proven that it always works THEORY When supported over time Only call on those with misconceptions The rest of what we will be doing is exploring the validity of this HYPOTHESIS