Scientific Laws

 

Scientific Laws, Hypotheses, and Theories

 

 

Scientific Theory versus “Just a theory” Layman’s term:

In layman’s terms, if something is said to be “just a theory,” it usually means that it is a mere guess, or is unproved. It might even lack credibility. But in scientific terms, a theory implies that something has been proven and is generally accepted as being true.

Scientific Meanings:

SCIENTIFIC LAW: This is a statement of fact meant to describe, in concise terms, an action or set of actions. It is generally accepted to be true and universal, and can sometimes be expressed in terms of a single mathematical equation. Scientific laws are similar to mathematical postulates. They don’t really need any complex external proofs; they are accepted at face value based upon the fact that they have always been observed to be true. Specifically, scientific laws must be simple, true, universal, and absolute. They represent the cornerstone of scientific discovery, because if a law ever did not apply, then all science based upon that law would collapse.  Some scientific laws, or laws of nature, include the law of gravity, Newton’s laws of motion, the laws of thermodynamics, Boyle’s law of gases, the law of conservation of mass and energy, and Hook’s law of elasticity.

HYPOTHESIS: This is an educated guess based upon observation. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation.

THEORY: A theory is more like a scientific law than a hypothesis. A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. One scientist cannot create a theory; he can only create a hypothesis. Theories may be expanded or modified with further scientific evidence.

Development of a Simple Theory by the Scientific Method:

  • Start with an observation that evokes a question: Broth spoils when I leave it out for a couple of days. Why?
  • Using logic and previous knowledge, state a possible answer, called a Hypothesis: Tiny organisms floating in the air must fall into the broth and start reproducing.
  • Perform an experiment or Test: After boiling some broth, I divide it into two containers, one covered and one not covered. I place them on the table for two days and see if one spoils. Only the uncovered broth spoiled.
  • Then publish your findings in a peer-reviewed journal. Publication: “Only broth that is exposed to the air after two days tended to spoil. The covered specimen did not.”
  • Other scientists read about your experiment and try to duplicate it. Verification: Every scientist who tries your experiment comes up with the same results. So they try other methods to make sure your experiment was measuring what it was supposed to. Again, they get the same results every time.
  • In time, and if experiments continue to support your hypothesis, it becomes a Theory: Microorganisms from the air cause broth to spoil.

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Scientific Method activity

Scientific Method I’m All Thumbs”
Introduction:
What makes a “Class Champion” thumb wrestler? Does thumb diameter, length, or wrist diameter have an effect on the overall chances of winning a thumb wrestling match? In this investigation we will develop a hypothesis based on physical data collected from our classmates. We will then test this hypothesis by conducting a thumb wrestling tournament to determine an overall “Class Champion”.

Materials:
Metric ruler, metric tape measure (see bottom of lab), scissors, string, calculator

Objectives:

  • Students will take and record accurate measurements of their wrist, and their thumb’s circumference and length.
  • Students will analyze the data collected and determine if their hypothesis is correct.
  • Correctly line graph the collected data.
  • Learn the rules of thumb wrestling.
  • Conduct a thumb wrestling tournament.

Procedures:

  • Choose a partner and perform the following measurements using the metric tape measure found at the bottom of this lab. Then have your partner perform them on you.
  • Measure the circumference of the thumb, in centimeters, at its widest point. Record this data on the following line ___________cm. and on the table on the chalk board.
  • Measure the length of the thumb, using the metric ruler in centimeters, from its tip to the end of its second joint. Record this data on the following line ___________cm. and on the table on the chalk board.
  • Measure the circumference of the wrist over the ulnar knob, in centimeters, and record this data on the following line ____________ and on the table on the chalk board.
  • Copy the data, on the board, on to the table in the results section of the lab.
  • The class will form and record a hypothesis based on the collected data.
  • The Hypothesis:
    ______________________________________________________________

        ______________________________________________________________

  • Rules of thumb wrestling: Two players grasp hands shown in the illustration; they touch thumbs to the opposite sides of the other person’s hand three times, then come out wrestling. The object, of course, is to hold the other person’s thumb down, for a count of three, using only your thumb.

 

  • Boys will wrestle boys and girls will wrestle girls.
  • A tournament schedule will be set up to match opponents.
  • After the completion, a champion will be declared in both categories, (male and female).

Results:
Complete the following data table:

 

Student Name
Gender (M / F)
Thumb Circumference in cm
Thumb Length in cm
Wrist circumference in cm
Record
( won/ lost)
Optional
1.aaaaaaaaaaaaaaaaa
M / F
2.aaaaaaaaaaaaaaaa
M / F
3.aaaaaaaaaaaaaaaa
M / F
4.aaaaaaaaaaaaaaaa
M / F
5.aaaaaaaaaaaaaaaa
M / F
6.aaaaaaaaaaaaaaaa
M / F
7.aaaaaaaaaaaaaaaa
M / F
8.aaaaaaaaaaaaaaaa
M / F
9.aaaaaaaaaaaaaaaa
M / F
10.aaaaaaaaaaaaaaaa
M / F
11.aaaaaaaaaaaaaaaa
M / F
12.aaaaaaaaaaaaaaaa
M / F
13.aaaaaaaaaaaaaaaa
M / F
14.aaaaaaaaaaaaaaaa
M / F
15.aaaaaaaaaaaaaaaa
M / F
16.aaaaaaaaaaaaaaaa
M / F
17.aaaaaaaaaaaaaaaa
M / F
18.aaaaaaaaaaaaaaaa
M / F
19.aaaaaaaaaaaaaaaa
M / F
20.aaaaaaaaaaaaaaaa
M / F
21.aaaaaaaaaaaaaaaa
M / F
22.aaaaaaaaaaaaaaaa
M / F
23.aaaaaaaaaaaaaaaa
M / F
24.aaaaaaaaaaaaaaaa
M / F

 

Graph Title: ____________________________________________________________


Analysis and Conclusion :

1. Restate your hypothesis: __________________________________________________

2. Which students won? (male) __________________________ and (female)_____________________

3. What were their measurements:

male: thumb circumference: ____________, thumb length ______________, and wrist circumference ______________;

female: thumb circumference:__________, thumb length _________, and wrist circumference ______________.

4. What was the mean thumb circumference of the class? _____________cm

5. What was the mean wrist circumference of the class? ______________cm

6. Did all those with larger measurements win their matches? ____________.

7. Was you hypothesis correct? ______________.

8. If not, explain what was different. 

_____________________________________________________

_____________________________________________________

_____________________________________________________

9. What is the independent variable? _____________________________________

10. What is the dependent variable? ______________________________________

11. List the controlled variables in this experiment. 

         __________________________________________________

__________________________________________________       

11. Would this be considered a controlled experiment? ____________.

12. Explain your answer.

_____________________________________________________

_____________________________________________________

_____________________________________________________

Here is a sample tournament grid : Cut and turn sideways.

_______________________________________________________________________

_______________________________________________________________________

 

Cut and use.

________________________________________________________________________

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Second Semester Study Guide Bl

 

Second Semester Review 

 

Are animals autotrophs or heterotrophs? Explain.
What type of symmetry does a sea anemone have?
At which end of an animal is the tail located?
What supportive rod along the back do all chordates have at some time during their life?
How do sponges differ from all other animals?
How does a sponge obtain its food?
What hard, needle like structures are found in the walls of sponges?
Do all animal cells have cell walls? Explain.
In what phylum are squid & octopus found?
Name 4 animals that are classified as cnidarians.
What is the function of collar cells in sponges?
Are animals unicellular or multicellular organisms?
At which end of an animal is the head located?
What kind of symmetry do insects have?
Flatworms use what method to asexually reproduce?
Why do flatworms NOT need circulatory & respiratory systems?
What group of worms has a pseudocoelom?
What is the function of the radula in mollusks?
Which class of mollusks uses “jet propulsion” to move?
Describe torsion in gastropod mollusks.
Give several examples of appendages in arthropods.
Describe the body of all arthropods.
Describe the appendages of all arthropods.
In what group are clamworms found?
Name 3 main classes of mollusks.
What muscles open & close bivalve mollusks?
What makes up the exoskeleton of arthropods?
Name 4 members of the class Crustacea.
What group of animals has 3 body regions & 6 legs?
How do insects benefit agricultural crops?
Name 4 characteristics of all chordates.
In what order are amphibians without tails found?
From what structure in fish did jaws probably arise?
List 4 examples of echinoderms.
What structure in fish filters wastes from blood?
The urinary bladder & kidneys in fish make up what system?
Where are shark eggs fertilized?
What does “Agnatha” mean?
What does “Chondrichthyes” mean?
Describe caecilians.
Name 4 things used by sharks to detect their prey.
What type of symmetry do echinoderms have?
Why do most amphibians have thin, moist skin?
What does “amphibian” mean?
Describe development in placental mammals.
Where is the diaphragm found in mammals?
Name a reptilian characteristic found in birds.
What covers the body of birds?
What covers the body of reptiles?
Describe a reptile’s skin.
Are reptiles ectotherms or endotherms? Explain.
Where are the chorion & amnion found?
How many chambers does a bird’s heart have?
What adaptation of reptiles allowed them to live & reproduce on land?
How many chambers does the heart of most reptiles have?
How many chambers does the heart of mammals have?
Which group of vertebrates has a diaphragm & what is its function?
Are mammals endotherms or ectotherms?
Name 3 groups of ectothermic vertebrates.
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Scientific Method & Blood Flow

 

Scientific Method & Blood

 

INTRODUCTION:

In this lab you will learn to form a hypothesis, conduct experiments around that hypothesis, and collect and analyze data. One of the most important characteristics of modern science is its quantitative approach to solving problems. One of the first scientists to use quantitative methods was William Harvey, who discovered that blood circulated through the body. At the time Harvey began his work, anatomists believed that the liver produced blood from the food that the body consumed. The blood was then carried by veins to the heart, purified in the lungs, and then pumped to the various organs of the body, where it was consumed. Harvey measured that the left ventricle of the heart held roughly 100 ml of blood. He also measured that the heart beats an average of 64 times per minute.

QUESTION 1:

From the information above, and assuming that 1 ml of blood weighs 1 g, how much blood would the body need to produce per hour in ( g/hr.) to replace the blood consumed by the organs? _______g/hr.

Harvey hypothesized that the same blood must circulate continuously throughout the body.

MATERIALS:

Watch with second hand, or clock

PROCEDURE:

  1. While sitting quietly at your desk, find the pulse in your wrist and count the beats for one minute. You and your lab partner can do this on yourselves, or each other. Record the names of both subjects and their beats per minute heart rate on DATA TABLE 1 as sample 1.
  2. Repeat step 1 two more times for each subject. Record the data in the appropriate place on DATA TABLE 1.
  3. Calculate the average pulse rate for each subject and record the results on DATA TABLE 1.

How do you think standing or holding your breath will affect your pulse rate? ______________________________________________________

QUESTION 2:

Choose one of these activities and formulate a hypothesis about its effect on pulse rate. What is the independent variable? What is the dependent variable?

Hypothesis _______________________________________________

Independent Variable _______________________________________

Dependent Variable ________________________________________

  1. Repeat steps 1, 2, and 3 for each subject, this time with the subjects standing or holding their breath. Record your data and calculations in the appropriate DATA TABLE

 

 

DATA TABLE 1: Resting heart rate
NUMBER OF BEATS PER MINUTE AVERAGE NUMBER OF
BEATS PER MINUTE
SUBJECT sample 1 sample 2 sample 3

 

 

 

DATA TABLE 2: Heart rate standing
NUMBER OF BEATS PER MINUTE AVERAGE NUMBER OF
BEATS PER MINUTE
SUBJECT sample 1 sample 2 sample 3

 

 

 

DATA TABLE 3: Heart rate holding breath
NUMBER OF BEATS PER MINUTE AVERAGE NUMBER OF
BEATS PER MINUTE
SUBJECT sample 1 sample 2 sample 3

 

Conclusion:  Compare your data from step 4 with your data from step 3.

1. How do your results in step 4 compare with the hypothesis you made?

 

2. What measurement did you use as a control in this investigation?

 

3. What are some possible sources of error in this experiment?

Scientific Method PPT Questions

 

Scientific Method
ppt Questions

Steps in the Scientific Method

1. Name the steps in the scientific method.

 

2. Explain a scientist’s first step in the scientific method.

 

3. Give an example of an observation that a scientist might make.

 

4.Scientists use their __________ to make observations.

5. What is a hypothesis?

 

6. A hypothesis must be _____________ and it __________ an outcome.

7. Some hypotheses are written as __________ statements. 

8. Write a hypothesis for the observation you wrote in question 3.

 

9. What is an experiment?

 

10. What part of an experiment is the variable?

 

11. How many variables should there be in a good experiment?

Controls and Variables

12.An experimenter changes ______ factor and then observes and _______ what happens.

13. Other factors in an experiment must be kept __________ so they won’t effect the ___________.

14. What are these constant factors called?

15. What is the purpose of having a control in an experiment?

16. Name the two types of variables in an experiment.

17. What is the independent variable?

 

18. What is the independent variable?

 

19. In the experiment to find the fastest route to school, what serves as:

     a. the independent variable?

     b. the dependent variable?

     c. the control variable?

20. The best experiments make __________ trials with the independent variable.

Valid Experiments

21. Name the two group needed to have a valid experiment.

22. What is data?

23. What are the two types of data?

24. If the data is numbers, this is called ____________ data.

25. To be useful, collected data must be _____________.

26. Name 3 ways of organizing data.

27. What is the conclusion of an experiment?

 

28. What must be done to verify the results of an experiment?

Review

29.To solve a problem, you should _________ the problem and state _____________ you have made about it.

30. Next, you form a __________ or prediction and conduct an ____________ to test the prediction.

31. During an experiment, _________ must be collected and later ____________..

32. Finally, a scientist forms a ____________ based on your data.

33. To prove the experiment is correct, scientists ___________ their results.

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