Section 1: The Methods of Science Identify the steps that scientists often use to solve problems. Describe why scientists use variables. Compare and contrast science and technology. Science studies natural patterns. Science is classified into three main categories: life science, Earth science, and physical science. Science explains the natural world; explanations can change over time. Ancient Greek philosophers thought that everything was composed of five basic elements: ▪ earth, air, fire, water, and aether Scientists investigate nature by observation, experimentation, or modeling. Scientific method: organized set of investigation procedures 1. State a problem. 2. Gather information 3. Form a hypothesis based on knowledge and observation. Hypothesis: TESTABLE statement that is used to set up an experiment! 15 year old males are taller than 15 year old females The Steelers are better than the Ravens Dinosaurs were blue in color Bacteria do not need oxygen to survive 4. An experiment with variables is a common way to test a hypothesis. Experiment: a test of the effect of one variable on another using controlled conditions. Variable: a quantity that can have more than a single value. a) An independent variable is the variable changed in an experiment to see the effect. b) A dependent variable is the variable that changes as a result of the independent variable. c) A variable that does not change when other variables change is a constant. d) A control is the standard to which test results can be compared. 5. Analyze data from an experiment or investigation. Plant Amount of Water Amount of Sun Height after two weeks A 4 oz. every three days 6 hr/day 18cm B 4 oz. every three days 0 hr/day 6cm 6. Form a conclusion based on the data. 7. Reduce bias by keeping accurate records, using measurable data, and repeating the experiment. Bias: occurs when what the scientist expects changes how the results are viewed. Model: represents an idea, event, or object to help people better understand it. All models have limitations. Theory: an explanation based on MANY observations and investigations Scientific law: is a statement about something in nature that always seems to be true. A theory can never become a law! Instead theories are used to explain laws. Science deals with the natural world; questions of value or emotion cannot be answered. Technology: applied science helping people Explain why a control is needed in a valid experiment. What is the dependent variable in an experiment that shows how the volume of gas changes with changes in temperature?