Steps in the Scientific Method 1.Observations - quantitative - qualitative 2.Formulating hypotheses - possible explanation for the observation 3.Performing experiments - gathering new information to decide whether the hypothesis is valid whether the hypothesis is valid

Observation The scientific method begins with observations to be further investigated. Observation allows a problem or question to be formulated.

Hypothesis An educated guess based upon observations of what is expected to happen. A tentative explanation that must be tested. Cannot be proven, only supported or refuted. “A hypothesis is nothing without an experiment to support or refute it.”

Experiment »A set of controlled observations and measurements to test a hypothesis. »Variable-a condition or quantity that can have more than one value. »Should only investigate one variable at a time. All other variables should be controlled (stay the same).

Types of variables Independent variable - the variable that is changed. Dependent variable -the outcome variable-the variable is observed as the independent variable is systematically changed. Controlled variables -the variables that remain the same while the independent variable changes.

Data Analysis The experiment generates data that must be explored and analyzed. Graphs and charts should be made to interpret what data means.

Conclusion A judgment that is made about the experiment based on the data. If the hypothesis is supported by the data, further experiments need to be done to confirm the results. If the hypothesis is not supported by the data, a new hypothesis should be formed and the scientific method repeated.

Outcomes Over the Long-Term Theory (Model) - A set of tested hypotheses that give an overall explanation of some natural phenomenon. overall explanation of some natural phenomenon. Natural Law - The same observation applies to many different systems different systems - Example - Law of Conservation of Mass

Law vs. Theory A law summarizes what happens  A law summarizes what happens  A theory (model) is an attempt to explain why it happens.

Uncertainty in Measurement A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

Why Is there Uncertainty?  Measurements are performed with instruments  No instrument can read to an infinite number of decimal places Which of these balances has the greatest uncertainty in measurement?

Precision and Accuracy Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several measurements made in the same manner. Neither accurate nor precise Precise but not accurate Precise AND accurate

Types of Error Random Error (Indeterminate Error) - measurement has an equal probability of being high or low. Systematic Error (Determinate Error) - Occurs in the same direction each time (high or low), often resulting from poor technique or incorrect calibration.