The Scientific Method

How do scientists obtain new information? Observation Experimentation Discovery

What is an observation? An observation is a description of an object or event by using one of the 5 senses It is a statement that is 100% true, it is a fact

For example: The Grass is wet

Observations Use of one or more of the five sense to gather information There are two types 1) Qualitative observation: usually made with our sense; color, shape, feel, taste, sound (ex. Olivia is wearing blue jeans.) 2) Quantitative observation: How many? Will always have a number based on exact measurement (ex. The dog weighs 40.8 kg)

What is an inference? An inference is something that explains observations based on information that is observed When you infer something based on factual information it is 100% your opinion!

Inference It rained outside

Inferences A logical interpretation of an event that is based on observations and prior knowledge. You are in the office picking up the homework you forgot at home but someone brought up for you. You see a student leave the principals office crying and upset. We could make an inference as to why the student is upset. Could be in trouble (ISS, OSS, expelled) Family problems at home (accident, sick) Student is not feeling well Student has poor grades and is failing or being retained in there current grade.

What is the Scientific Method? The scientific method is a series of steps used by scientists to answer questions and solve problems There are 7 steps to the scientific method

Steps of the Scientific Method Purpose State the problem or ask a question Step 2 Research Find out about the topic (Background research) Step 3 Hypothesis Predict the outcome to the problem Step 4 Experiment Develop an experiment to test the hypothesis (Experiment must be reproducible) Step 5 Observations/Analysis Record the results of the experiment (Analyze your data) Step 6 Conclusion Compare the hypothesis to the experiment’s conclusion (Report your results) Step 7 Repeat the experiment

Parts of an Experiment Controlled experiment – an experiment where the scientist controls all the variables except the ONE variable being tested Experimental Group: the part of the experiment that is being tested Control Group: the part of the experiment that stays the same or is kept closest to normal conditions Independent Variable: The thing that differs between both groups (this is what the scientist is changing!) Dependent Variable: The thing that is not controlled by the scientist (the data collected!), it will be the results of the experiment Control factors or constants: all of the things that are kept the same between both groups

What is a Hypothesis? A hypothesis is a suggested answer to a problem without the support of data An educated guess or a prediction A hypothesis is always made BEFORE the experiment is performed and is never changed during an experiment Write as an “If…, then” statement For example: If we drop a tennis ball from a higher height, then it will bounce higher. “If” is the independent variable “Then” is the dependent variable

Example Group 1 Group 2 3 trees All have the same volume of water and same amount of sunlight 3 trees All have same volume of water, same amount of sunlight, and same amount of fertilizer

Two Types of variables Independent variable: the variable I (the scientist) change in the experiment Dependent variable: the variable that is being measured (the data collected) For example: I want to measure the effect of the sun on plant growth. What I change? The amount of sunlight What I measure? Plant growth

The effect of the Independent variable on the Dependent variable! For example The effect of the sunlight on the growth of plants. The effect of cold medicine on the number of sneezes. The effect of bleach on the growth of bacteria. Independent Variable (IV) Dependent Variable (DV)

What makes a good experiment? Repeating the experiment! Every scientist from around the world should be able to repeat your experiment and obtain the exact same results! Large sample sizes! Results are much more reliable when there are more subjects.

Theory In science it’s meaning is very different than in everyday life ‘The detective has a theory about who robbed the bank.’ This is a guess, when a scientist uses the word theory it is not used as a guess In science a theory is an explanation based on many observations during repeated experiments that is valid only if it is consistent with observations, makes predictions that can be tested, and is the simplest explanation

Theory continued The theory of gravity, theory of electricity, the germ theory of disease, and the theory of evolution are tested, accepted explanations for events that occur in nature Theories can really never be completely proven, only disproven When new evidence comes along, we must modify our theory or at times even get rid of it and start over again If even one experiment disproves the theory then it must be taken back to the drawing board

Example The geocentric theory that has the Earth as the center of our solar system is an example of what can happen when new evidence comes along Nicolaus Copernicus and Galileo Galilei provided mathematical and supporting physical observations that disproved the geocentric theory and as a result they proposed a new theory based on the new evidence This theory is known as the heliocentric theory where the sun is the center of our solar system and still stands as the accepted theory today

In the Beginning Aristotle (384BC-322BC) Ancient Greek Philosopher His work influenced thinking from his time to the present time He was so influential at the time that his mistakes were not noticed Believed that all problems could be solved by thinking about them. For example, he thought that heavy objects would fall faster than lighter ones

Aristotle The idea that heavy objects would fall faster then lighter objects seems reasonable right? That is how “science” was in ancient times What did Aristotle never do? It wasn’t until almost 2,000 years later for that to happen

Galileo Galilei 1564AD-1642AD Considered the first true scientist Why??? To Aristotle's idea that heavy objects fall faster than lighter ones Galileo asked, “How much faster?” He did an experiment to measure the difference in time between the two objects hitting the ground, these objects were of different mass’ being dropped at the same time from the same distance

What happened? Of course we know today what happened in that experiment To everyone’s surprise both balls hit the ground at about the same time! Isn’t it better to test your ideas rather than merely think about them? “One test is worth a thousand expert opinions.” –Bill Nye

Key Ideas Experiments are very useful and should be done to test ideas When conducting an experiment, change ONE factor and keep everything else exactly the same. Why? The thing you change is called the variable There are two types of variables 1) Dependent Variable 2) Independent Variable The things that you keep the same are called controls

Variables The thing you change is called the variable There are two types of variables 1) Dependent Variable: Something that depends on other factors (speed, height, etc.) 2) Independent Variable: A variable that stands alone and isn’t changed by the other variable that you are trying to measure (temperature, time, etc.)

Back to Galileo’s Experiment What were the variables in Galileo’s experiment? What were some controls?

Quick Review Control Independent Variable Dependent Variable The factors of the experiment that stay the same throughout the entire experiment Factor in an experiment that a scientist changes purposefully Factor in an experiment that a scientist wants to observe, which may change because of the independent variable Dropped from the same height Dropped at the same time Same shape The weight of the objects The speed that the objects fell at

Graphing Graphs are a useful tool in science The visual characteristics of a graph make trends in data easy to see and understand One of the most valuable uses for graphs is to “predict” data that is not measured on the graph

Identify the variables Number and label each axis Graphing Steps Identify the variables Determine the range Determine the scale Number and label each axis Plot the points Draw the graph Give your graph a title!

Identifying the Variables Independent variable (the thing you changed) Goes on the x-axis (horizontal) Should be on the left side of a data table Dependent variable (changes with the independent variable) Goes on the y-axis (vertical) Should be on the right side of a data table

Important Know the range of your data! Subtract the lowest data value from the highest data value and that is the range This needs to be done with each variable separately Have an appropriate scale! This is the numerical value for each square, it should best fit the range for the particular variable Maximize the space available

Plotting & Labels! Plot each data value on the graph with a small dot, a shape may be placed around the dot if necessary but try to keep the clutter on your graph to a minimum You need to tell anyone reading your graph what the graph means Graph title X-axis title Y-axis title Include appropriate units

Drawing & Title Draw a curve or a line that best fits the data points of your experiment Most graphs of experimental data are not drawn as “connect-the dots” but rather as a line of best fit Your graph title should clearly tell what the graph is about If your graph has more than one set of data a “key” should be provided to identify the different lines

Title Your graph title should clearly tell what the graph is about If your graph has more than one set of data a “key” should be provided to identify the different lines

Now it’s your turn to try graphing!