HOW SCIENTISTS WORK USING CORRECT SCIENTIFIC METHODS WHAT

HOW SCIENTISTS WORK USING CORRECT SCIENTIFIC METHODS

WHAT IS A HYPOTHESIS? • A reasonable explanation of an observation or experimental result or a possible answer to a scientific question that can be answered. • The hypothesis may or may not be supported by experimental results.

HYPOTHESIS, CONT. • Often stated as a cause and effect relationship. Usually written as “if…then” statements If…then… EX: If a leaf has a larger surface area, then the rate at which it produces oxygen may increase.

KNOW HOW TO USE EQUIPMENT SAFELY AND PRECISELY • Know and follow all lab safety rules! • Use SI units. • Precision is the degree to which measurements are consistent. • Accuracy is the degree to which values agree with the true or accepted value.

It is possible to have a high degree of precision with poor accuracy. EX: You use the same balance to measure mass changes during an experiment. However, the balance wasn’t calibrated to truly measure grams.

HOW ARE EXPERIMENTS DESIGNED? • Experiments must have constants – only one variable is tested at a time. All variables are held constant except for the one being tested. EX: To determine how temperature affects plant growth, the plants must be the same species, be in the same type of soil, have the same amount of water, have the same amount of light, etc. Only the temperature will be different.

STEPS IN DESIGNING AN EXPERIMENT • State the purpose in the form of a question • Research information (asking scientists, credible Internet resources, scientific journals, etc. ) • State the hypothesis

• Plan the experiment – independent (deliberately changed by the experimenter) and dependent variables (changes in an experiment in response to changes in the independent variable) repeated trials plan to hold variables constant list and obtain materials plan to organize data (make tables, etc. )

may need a control group – used as a basis of comparison • Analyze data (graphs, etc. ) • Make a conclusion that may or may not support the hypothesis

ORGANIZATION OF DATA (GRAPHS) • • Independent variable on X axis Dependent variable on Y DRY MIX!! The dependent or responding variable goes on the Y axis. The manipulated or independent variable is graphed on the X axis. • • Intervals on each axis should be in equal increments Each axis must be labeled (name of variable and units)

• Title the graph with a descriptive title • Use the appropriate type of graph line graph – continuous data bar graph – categorical data circle graph – usually involve %