The Scientific Method www.youtube.com/watch?v=KZaCy5Z87FA&feature=related www.youtube.com/watch?v=RU1DZeqY4To

THE SCIENTIFIC METHOD http://glencoe. mcgraw-hill Question Observation Hypothesis Experiment Data Conclusion

VARIABLES The different factors that can change in an experiment An experiment usually has three types of variables: independent, dependent and constant

INDEPENDENT VARIABLES (What I CHANGE in an experiment) This is the variable that you intentionally change throughout the experiment A good experiment has only ONE independent variable What are you physically doing to the experiment that might cause a change

DEPENDENT VARIABLES (What I OBSERVE) The variable that responds and changes because of the independent variable (because of what you did) Often measured at the end of the experiment

CONSTANT VARIABLES (What I Keep the SAME) These could change and affect your experiment, but you do not want them to This does not ever change in an experiment Ex. Do plants grow better in darkness? Constant variable would be the amount of water you give the plants

EXAMPLES OF VARIABLES QUESTION INDEPENDENT VARIABLE (WHAT I CHANGE) (WHAT RESPONDS) CONSTANT VARIABLE (WHAT I KEEP THE SAME) Does heating a cup of water allow it to dissolve more sugar? Temperature of the water measured in degrees Celsius Amount of sugar that dissolves completely measured in grams Amount of stirring Type of sugar Does fertilizer make a plant grow bigger? Amount of fertilizer measured in grams Growth of plant measured in centimeters Same size pot for each plant Same type of plant in each pot Same type and amount of soil in each pot Same amount of water and light Make measurements of growth for each plant at the same time Do bicycle fenders keep the rider dry when riding through a puddle? The bicycle either has fenders or does not The rider either gets wet or does not Same type of bicycle Same type of tires on bike Riding at the same speed Same size and depth of puddle Who listens to music the most: teenagers or their parents? The groups receiving the survey: teenagers or parents The amount of time that each person listens to music per day measured in hours Ask the question in exactly the same way to each individual

CONTROL A standard to which your results can be compared These are exposed to the same conditions as the experiment groups, but there is no variable being tested Examples: Growing plants in sunlight in a darkness experiment, no antibiotic on a bacteria study about testing new drugs (placebo group)

QUESTION CONTROL Does heating a cup of water allow it to dissolve more sugar? ROOM TEMPERATURE Does fertilizer make a plant grow bigger? NO FERTILIZER Do bicycle fenders keep the rider dry when riding through a puddle? NO FENDERS Who listens to music the most: teenagers or their parents COMPARISON STUDY—NO CONTROL

Procedures A list of materials needed to complete the experiment is given. Step by step directions for how the procedure is performed is given. Specific information for data collection are included.

IMPORTANCE OF REPEATING EXPERIMENTS For results to be considered valid, experiments need to be repeated countless times to be sure that the same results occur

Types of Data Qualitative: descriptions that do not include measurement. Examples would be color, texture, and appearance. Quantitative: a number and unit is given for an exact measurement. Examples would be 12 feet, 3 grams, and 4.2 liters.

Data Analysis For quantitative data, averages are often calculated. Totals are given for qualitative data. For example, 4 dogs were black and 2 were brown A graph is made of the averages so that it is easier to interpret. A sentence or two is given to summarize the numerical data.

Conclusion A summary of the experimental findings. Restates the hypothesis. Identifies whether the hypothesis was supported or rejected by the experiment. Provides a possible reason for the results. Discusses how the findings are useful. Proposes ways to improve the experiment and/or additional questions to be tested.

SCIENTIFIC THEORY An explanation or model for a scientific question that backs a hypothesis and is supported by results from many, many experiments The theory of evolution explains how organisms change over time in response to their changing environment

SCIENTIFIC LAW A rule that describes the behavior of something in nature A scientific law typically describes what will happen, but not why They are universally accepted as true Examples include Newton’s Laws of Motion, law of gravity