Scientific Processes (The Scientific Method)

What is Science? Science is an organized way of using evidence to learn about the natural world. Skills Used By Scientists: Observations skills – scientists use their senses (sight, hearing, touch, smell, and sometimes taste) to observe nature Hypothesizing skills – scientists attempt to explain the observations by forming hypotheses or ideas Analyzing and Interpreting skills – scientists analyze and interpret data collected during experiments while using prior knowledge and experience

How Scientists Work Design an experiment: (Using Scientific Method) State the Problem Collect Data (Observation) Form a Hypothesis Set up a Controlled Experiment to Test Hypothesis Record and Analyze Results (Data) Draw a Conclusion Based on Analysis Publish and Repeat Investigations (Theory)

Writing A Hypothesis Hypothesis – a possible explanation for a set of observations or possible answer to a scientific question. It must include your independent variable and your dependent variable. Make sure you use these in a way that you can readily measure. If …. then

Example Problem – Why did uncollected seeds germinate but seeds kept indoors did not germinate? Hypothesis – If seeds are stored indoors in cold conditions, then they will germinate in the same way as seeds left outdoors during the winter

Designing Controlled Experiments Variable - changing quantities 3 Types of variables: Controlled Variable/s – the variable/s that are purposely kept the same Independent Variable(manipulated variable) – the ONE variable that is deliberately changed Dependent Variable(responding variable) – the variable that is observed and that changes in response to the manipulated variable Whenever possible, a hypothesis should be tested by an experiment in which only ONE variable is changed at a time. (AKA: Controlled Experiment) Experimental Group – the group in which the independent variable is changed Control or Control Group – the group used as a standard for comparison for the experimental group

Controlled Experiment Example Hypothesis: If a tomato plant is fertilized, then it will produce more tomatoes than a plant that is not fertilized. Plant A Plant B * Both plants were given the same starting soil, amount of water and sun, temperature, pot size, and growth time. Plant B was fertilized once a week. What are the controlled variables, the independent variable, and the dependent variable? Which is the control and the experimental group?

Answers Controlled Variables – starting soil, amount of water and sun, temperature, pot size, and growth time Independent Variable – fertilizer Dependent Variable – number of tomatoes Control – Plant A Experimental Group – Plant B

Why change only one variable? Plant A Plant B Plant A is given sunlight for 5 hours a day, l L of water every 4 days, a quart sized pot, and kept at 30°C for 6 weeks. Plant B is given sunlight for 7 hours a day, l L of water every 2 days, a gallon sized pot, kept at 35°C for 9 weeks, and given fertilizer once a week. Why did plant B grow more tomatoes? By only changing one variable, the experimenter can conclude that changes in the dependent variable are due exclusively to changes in the one independent variable.

VARIABLES INDEPENDENT variables answer the question "What did I change?".” “What caused the measurement to change? DEPENDENT variables answer the question "What do I observe?". “What’s being measured?” CONTROLLED variables answer the question "What do I keep the same?".