Methods of Science

Chapter 1.3 pages 16-21

• The Scientific Method: Steps used to gather data and answer questions.

The Scientific Method

• The scientific method generally follows a pattern:1. Ask a question2. Make observations3. Form a Hypothesis4. Experiment5. Collect and analyze

data6. Draw conclusions

1. Ask A Question and2. Make an Observation

• Scientific inquiry begins with observation. Observation is the act of noting or perceiving objects or events using the 5 senses.

• Combining your observation with your past knowledge allows you to make inferences, or logical conclusions.

Observation vs. Inferences

• Inferences are an explanation for an observation that you have made.

• Inferences often change when new observations are made.

Observation: The grass is wet.Inferences: It rained. OR

The sprinklers went off.

3. Hypothesis

• A hypothesis is a TESTABLE explanation for your question.– This statement can be tested by additional

observations or experimentation.– An educated guess based on what is already

known– Usually written as an “If/then”statement.

4. Experiment

• Experiment – a planned procedure to test a hypothesis.

• Controlled experiment – an experiment where an experimental group is compared to a control group.– Control group is a group in an experiment that

receives no experimental treatment.– An experimental group is the group exposed to

the factor being tested.

Experimental Design

• Both control and experimental groups are designed to be identical except for one variable.

• Variables - factors, conditions, and/or relationships that can change or be changed in an event or system.

Three kinds of variables in a scientific investigation:

• The factor that is varied/changed in an experiment is called the independent variable.

• The variable that is measured in an experiment is called the dependent variable.

• A constant is a factor that remains fixed during an experiment.

Memory Trick

DRY

MI X

Dependent

Responding

Y-axis

Manipulated

Independent

X-axis

What were the independent and dependent variables for our paper towel lab?

• Independent variable – the mass of the plane based on the number of paper clips added.

• Dependent variable – the distance flown.

• Controlled variable – the fact that the same plane was used for each trial.

Identifying and Manipulating Variables

Example: A student wanted to test how the mass of a paper airplane affected the distance it would fly. Paper clips were added before each test flight. As each paper clip was added, the plane was tested to determine how far it would fly.

5. Collect Data

• Data is any information gained from observations.

• 2 types: • Quantitative – measureable or countable

» 3 meters long» 4 marbles» 50 kilograms» 35 degrees Celsius

• Qualitative – describable, not measureable » red flowers» smells like fresh baked cookies» Tastes bitter

6. Analyze Data

• A graph of the data makes the pattern easier to grasp.

• On a graph, the x axis represents the independent variable

• the y axis represents the dependent variable

1. Human heart rate will increase from sitting to standing.

2. I have 3 different types of paper towels; I think type A will hold the most water.

3. Adding sugar to water will increase the temperature at which water boils.

4. The warmer an egg, the faster it will open.

Identify the independent and dependent variables in each example below and label the graph:

temp

timetemp

amt of sugar

amt ofwater

type of papertowel

heart rate

body position

7. Conclusion

• Once data are collected and analyzed, a hypothesis is either supported or rejected.

• Even when a hypothesis has not been supported, it is valuable.

• A hypothesis can be supported, but never proven because another experiment with new data can alter the conclusion.

• Publication– Scientists often publish the results of their experiments

for review and use by other scientists.

Form a Hypothesis

Hypothesis: an testable statement or prediction; an “if, then” statement

If ____independent variable______then__dependent variable_______

Example:

Independent Variable: I feed my cat a lot of food

Dependent Variableshe will get fat

If ___________________________then _________________________

Remember

Try to use INCREASE and DECREASE in your hypothesis!

Ex. IF I increase the amount of food I give my cat, THEN she will increase her weight

Practice

Use this hypothesis to identify the variables:

If I leave all the lights on all day, then my electric bill will be expensive

IV: ______________________DV: ______________________

If I brush my cat more, then there will be less fur on my furniture

IV: ______________________DV: ______________________

Now read the following experiment and identify the independent and dependent variables

Elizabeth wanted to test if temperature affected how fast milk goes bad and curdles. She left milk in a room temperature closet, a fridge, and a oven that was turned on low heat. She then measured how rotten the milk was after 10 days.

IV: ____________________________________

DV: ____________________________________