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Thinking Like a Scientist:
Overview of the Scientific Method
-is a process for experimentation that is used to explore observations and answer questions.
Scientist use the scientific method to search for cause and effects relationships in nature.
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In other words, they design an experiment so that changes to ONE item causes something else to vary in a predictable way. You will use this same method in our biology class and in fact you do use it everyday of your life to help you solve problems.
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For example: You went out to the car this morning and the car did not start. What now? Your cell phone will not turn on. What now? ect, ect, ect………………
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Make an observation
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
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Step 1: Making an observation: the act of studying objects or events using your senses Being a good observer is the most important aspect of being a good scientist!! Two types of observations can be made during the scientific process: 1. Qualitative observations 2. Quantitative observations
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Qualitative observations:
Root word?
Quality
Qualitative observations are:
-descriptive
-describe the quality of an object
-involve characteristics that can’t easily
be measured.
-Obtained by using your senses.
-Examples:
color, texture, smell
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Quantitative observations:
Root word?
Quantity
Quantitiative observations are:
expressed with numbers
obtained by counting or measuring.
Example:
mass, volume, temperature, length
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Apples:
Quantitative observations:
Qualitative observations:
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Many observations lead to questions.
Why?
When?
Where?
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10. Step 1: Observation of a problem/Ask a question
Example:
Today all is well.
Tomorrow you come into class and our fish is dead.
Our question?
Why did the fish died?
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Step 2: Many observations lead to questions. Do some additional background research on your subject What do we know about fish????
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12. Explaining and Interpreting Evidence
Step 3: Form a hypothesis.
A hypothesis is explanation that you come up with for what you observed. It must be testable.
-know an “Educated Guess”
Why?
-educated because it is based on prior knowledge or you did some background research on the fish.
-a guess because it can be proven true or false.
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13. Explaining and Interpreting Evidence
The best method of forming a hypothesis:
- must be proposed in a way that can be tested.
-it must be in the form of a statement
-it can not be in the form of a question
Best if you use a:
-If…………then……….. statement
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Form a hypothesis as to why our fish died: Examples of a well formed hypothesis for our fish scenario: If……………………. then………………
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Step 4: Scientist then set up and perform controlled experiments.
-An experiment is a set of planned steps used to test a hypothesis
-A controlled experiment test one factor at a time.
It is made up of:
1. One Control group
2. One or more Experimental group
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The one control group
Gets not experimental treatement.
It is set up as close to normal conditions as possible/serves as a standard of comparison.
One or more Experimental group:
The experimental groups are the same as the control group, except for the one factor, the experimental variable is altered in each experimental group
The variable is the
factor that is being tested by the
experiment.
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Parts of an experiment:
Constants:
Variable:
Control group:
Experimental group(s):
Factors that are the same in all groups
The factor that is being tested in the experiment
The setup that is as close to normal conditions as possible
is the same as the control group, except for the one factor or variable that is being tested.
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Our thoughts: The fish died because the temperature of the water was too hot.
Our hypothesis: If the water was too hot
then the fish would have died.
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Our controlled experiment will have four set ups 1 Control group (as close to normal conditions as possible for a goldfish) and 3 Experimental groups (each identical to the control setup except for the one variable that is being tested). Our experimental variable will be temperature.
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Our Control setup:
As close to normal conditions as possible;
room temp (22 degrees Celsius) , 1 of the same type of plants
3 gallons purified water , 50 grams of stones
3 fish (same age and type), .5 grams of food each day,
14 hours of light , pH of 7
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Our three Experimental Setups:
tank 1 tank tank 3
12 degrees degrees degrees
In each tank: 3 gal purified water , 50 grams of stones
3 fish (same age and type), .5 grams of food each day,
14 hours of light , pH of 7 and 1 of the same type of plants
What is the only difference between the 3 groups?
Our experimental variable is TEMPERATURE
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22. If all the fish in experimental tank two and three died, what conclusion might you draw?
Our control group: Our three Experimental Setups:
tank tank tank 3
22 degrees degrees degrees degrees
In each tank: 3 gal purified water , 50 grams of stones
3 fish (same age and type), .5 grams of food each day,
14 hours of light , pH of 7,2 of the same type of plants
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Step 5: Scientist collect data, analyze results and form a conclusion:
Scientist usually perform their experiments many times to be sure they get similar answers every time.
What is data?
is information collected during an experiment.
12 degrees
22 degrees
32 degrees
42 degrees
Fish 1
Slow moving
Slow respiration rate
10 breaths/min
Faster moving
Faster respiration rate
32 breaths/min
Died after 30 min
Died after 1 min
Fish 2
12 breaths /min
40 breaths/min
Died after 45 min
Died after 3 min
Fish 3
15 breathes / min
35 breaths /min
Died after 22 min
Died after 2 min.
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Scientist will make both quantitative and qualitative observations during an experiment. Which type do you think are more useful in science?? -Quantitative observations hold more weight -not based on a person’s senses -based on measurements -in science all quantitative data is collected using the International System of Measurement or using SI units
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Let us examine some of the most common quantitative observations you will be making in lab using SI units.
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Length:
distance between 2 points
SI base unit/label =
meter
Instrument or tool used to measure length?
metric ruler or meter stick
Divisions of a meter =
dm, cm, mm
Multiples of a meter =
Km, Hm, Dm
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Mass
The amount of matter in an object.
SI unit/label:
-grams (Kg, Hg, Dg, g, dg, cg, mg)
Instrument or tool to used to determine mass?
-Balance
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Mass is different than weight.
-Mass is a constant value, it is not influenced by the pull of gravity.
-Weight is based upon the pull of gravity. The pull of gravity varies based on an objects distance from the center of the Earth. .
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Top of mountain
Mass: 68 Kg
Weight: 147 pounds
Mass: 68 Kg
Weight: 150 pounds
Sea level
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Temperature: absence or presence of heat
SI base unit/label =
degrees Celsius
Instrument/tool used to measure:
Thermometer
Therm =
heat
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Let’s do a comparison
CELSIUS VS FAHRENHEIT
WATER BOILS
BODY TEMP
ROOM TEMP
WATER FREEZES
100
212 37
98.6 22 32
° C  x  9/ = °F
(°F  -  32)  x  5/9 = °C
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Volume:
-How much space an object occupies.
-Two types of volume: Liquid and solid
Liquid volume:
SI base unit/label =
liter (Kl, Hl, Dl, l, dl, cl, ml)
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Instrument used to measure liquid volume?
Graduated Cylinder
Flask
Beaker
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meniscus
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Solid Volume:
Amount of space an object occupies.
Length x Width x Height
SI label:
m3 or cm3
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Not all solids have a regular shape!!
Sometimes the length , width and height can not be determined
Regularly shaped Irregularly shaped
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Solid volume of a irregular shaped object
Use water displacement
to determine volume
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Water Displacement
Record volume of water in graduated cylinder ml
Add object
Record volume of water after object is added. 9ml
The difference is the volume of the object 2ml
Change unit to cm3
Answer: 2 cm3
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Once the observations are made and data is collected the scientist must analyze the results and draw their conclusions a. The scientist then forms a conclusion based upon the data collected. b. If the data supports their hypothesis they will then move on to step 6 c. If the data does not support their hypothesis they will then have to go back and form a new hypothesis and start experimenting all over again.
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Hypothesis is not supported….go back to step 3. (form a new hypothesis and experiment more) If the hypothesis was supported ……proceed to step 6
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Step 6: Scientist must replicate their work and truthfully share their work and results by publishing/reporting their results. -scientist must publish his/her results and procedures so others can replicate it. -other scientist will perform the experiment to insure the results are correct.
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Scientific understanding is always changing. Good scientists are skeptics who question both existing ideas and new hypotheses. Therefore, nothing in science is absolute. -constantly be updated -things are constantly improving
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Example: What is this?
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Hypothesis:
Educated guess / a testable explanation of an observation.
Scientific Law:
Describes what happens
ScientificTheory:
Explains many related observations and is supported by a large body of evidence acquired through scientific investigation
Examples: Cell theory, Theory of Evolution,
Plate Tectonic Theory
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Your boss thinks that a special juice will increase the rate in which his employees work. -He creates two groups of 50 workers. -Each group is given the same task to perform. -The task given to the workers is to staple a sets of papers. -Group A is given the 50 ml of a special juice to drink while they work. -Group B is not given the special juice, they are given 50 ml of water to drink.. -After an hour, your boss counts how many stacks of papers each group has made. -Group A made 1,587 stacks -Group B made 2,113 stacks
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Homer Simpson notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. -Homer decides to check this out by spraying half of the shower with 10 ml of coconut juice. -He sprays the other half of the shower with 10 ml of water. -After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower.
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