Scientific Method

A scientific method is a systematic approach used to answer a question or study a situation. It is both an organized method for scientists to do research and a method for scientists to verify the work of other scientists. A typical scientific method includes making observations, stating a problem, forming a hypothesis, performing an experiment, and arriving at a conclusion.

Problem The problem should be stated as a question.

1. What question is being asked? a. How much mechanical energy does the battery produce? b. How much pressure is created by an electric current? c. What is the pH of water during electrolysis? d. How much energy is converted to heat?

2. The table shows times required for water to evaporate from identical containers. Which of these is the best question to ask before developing a reasonable hypothesis to explain the data? A. Why does a lower temperature slow the rate of evaporation? B. Why does water exist as a solid at -15C and as a liquid at 25C? C. What is the boiling point of the water after both samples are heated? D. How does the rate of evaporation change when a different container is used?

Hypothesis The hypothesis is the answer to the problem and must be stated in a way that can be tested by an experiment.

DRY MIX Independent Variable - The variable that is changed on purpose by the experimenter. It is sometimes called the manipulated variable. This is the “if” part of a hypothesis. It is plotted on the x-axis. Dependent Variable - The variable that acts in response to the manipulation of the independent variable. It is sometimes called the responding variable. It is plotted on the y-axis.

Controlled Variables Controlled variables-Any other variable which might affect the value of the dependent value and is held constant.

4. Students placed equal amounts of bread mold on 12 identical agar plates containing the same amounts and types of nutrients. Four plates were kept at 0°C, four were kept at 45°C, and four were kept at 22°C (room temperature). The plates were examined after five days. Which of the following was probably the hypothesis for this experiment? The growth of bread mold increases as temperature increases. The size of the plates determines the temperature of bread mold. The type of nutrient causes bread mold to grow faster at higher temperatures. The temperature of bread mold is determined by the mold’s growth.

Controlled or Valid Experiment An experiment is conducted with one (and only one) independent variable and one (and only one) dependent variable while holding all other variables constant.

Controlled or Valid Experiment You now need to test your hypothesis by making a step-by-step procedure of what you will do Select only one variable to change in each experiment (independent variable). Change a variable that will help you test your hypothesis. The procedure must tell HOW you will change this variable. The procedure must explain how you will measure the amount of change. The procedure should indicate how many trials would be performed

Impossible Experiments You cannot conduct experiments on: 1. Dinosaurs 2. Stars

Observation vs. Inference Observation: Information obtained through the senses: sight, touch, smell, etc; often involves a measurement Sight Touch Smell Hear Inference: a conclusion based on the data collected

Observation vs. Inference Starring Homer J. Simpson

Observation Ohh… This liquid is green and it is leaking from a brown can. I also smell it. Observation: when studying something describe only facts that you can see, touch, smell and hear. You are not making any guesses. THIS IS NOT AN OPINION!!

THIS CAN BE A SCIENTIFIC OPINION Inference Based on my observations, I think that this can is old and is leaking a toxic substance. Inference: using your observations to make a guess about an object or an outcome THIS CAN BE A SCIENTIFIC OPINION

Pie Graphs Pie graphs are used to compare the parts of a whole. Data in the form of percents use pie graphs.

Line Graphs Line graphs are used to show the relationship between variables

Types of Relationships (between variables) Direct: as x increases y increases

Indirect: as x increases y decreases

Constant: as x increases y remains the same