Scientific Method and Controlled Experiments

Science and the Scientific Method Science is a way of learning about the natural world and the knowledge gained through that process The Scientific Method also called scientific inquiry is the diverse ways in which scientists explore problems and seek to answer questions about the natural world.

The Steps of the Scientific Method 1. Posing Questions 2. Developing a Hypothesis 3. Designing an Experiment 4. Interpreting Data 5. Drawing Conclusions

Posing Questions Experiments begin by asking a scientific question which is a question that can be answered by gathering evidence. An example is “Which freezes faster– freshwater or salt water?”

Developing a Hypothesis A hypothesis is a possible explanation for a set of observations or it can be an answer to a scientific question. A hypothesis must be something that can be tested. A hypothesis can be written in the form of an If....then.... Statement. An example is “If I add salt to fresh water, then it will take longer to freeze.”

Designing an Experiment An experiment should have only one variable that changes. Experiments have variables which are any factors that can change in an experiment The manipulated variable (or independent variable) is the one factor that you change in the experiment The responding variable (or dependent variable) is the factor that changes as a result of the manipulated variable, it is what you measure to obtain you results

Designing an Experiment In a controlled experiment all factors except one are kept constant Controlled variables are variables that are kept constant among all of the tested subjects of the experiment. Most controlled experiments include a control group or control subjects which are subjects that do not experience changes to the the manipulated variable but are kept at normal conditions

Interpreting Data The observations and measurements made during an experiment are called data. After conducting an experiment scientists analyze the data to look for patterns or trends. Data is often organized in a data table or graph to identify patterns and trends easier Scientists ask: Does the data support the hypothesis? Do they need to collect more data? Is there a flaw in the experiment?

Drawing Conclusions A conclusion is a statement that sums up what you have learned from an experiment. When scientists draw a conclusion they need to decide whether the data collected supports their hypothesis or not. An experiment may need to be repeated several times before a conclusion can be drawn.

Hypothetical Experiment If I want to see if adding fertilizer to plants helps them grow faster… What would be the manipulated variable? The amount of fertilizer added to plants What should be some controlled variables? Type of plants Amount of water given Amount and intensity of sunlight exposure Type of soil planted in Type of pot planted in Ambient temperature