1.5 The Scientific Method

Refer to page 12 of your notes

The Scientific Method is used by researchers to support or disprove a

theory. It can be used to answer True-False questions only.

For example: Not Valid : Why do giraffes have long necks?

At first glance, this question seems quite scientific.

However, questions of this type cannot be proven scientifically.

The best you can do is come up with a believable theory, such as

"Assuming Darwin's theory of evolution, giraffes with long necks have evolutionarily had an advantage over giraffes with shorter necks."

Refer to page 12 of your notes

1• Observation

• Use our five senses (sight,smell,hearing,taste & touch) and other equipment to make observations and gather information

2 • Question• Ask a question about what your observe

3• Hypothesis

• Analyse - Study the information closely• Predict - Propose a hypothesis to predict

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• Method• Plan Experiments to test your hypothesis• Decide (1) the purpose/hypothesis (2) what apparatus to use (3) what

procedures to take to ensure a fair test to prove the hypothesis• The outcome must be measurable (quantifiable)

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• Results• Record your results in a table form • Plot the experimental data to analyse/interprete the results (E.g: Bar Chart,. It

provides a clear visual description of the data)• If they do not support the hypothesis, (1) repeat the experiment or (2) change the

hypothesis and experimental procedures

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• Conclusion• You state whether your hypothesis was confirmed or not and try to explain your

results.• A conclusion will often lead to another question, which can lead to another

experiment, which can lead to another conclusion, and on and on. 

Refer to page 12 of your notes

Science is like doing a giant puzzle, with the handicap that you are missing an unknown number of pieces.

Questions

Experiment

Conclusion

Refer to page 12 of your notes

Detective Skills

Observation

Some of the skills that scientists use are the same as those used by detectives in solving a crime. Many crimes are solved because someone has made very careful observations.

Observations are things or events that you notice.

A footprint, the smell of perfume, the sour taste of a drink, an unusual sound, or a warm log in a fireplace could provide clues to a crime.

Normally, to make observations, you can use all your five senses. After making observations, you might be able to form a hypothesis about what happened.

Refer to page 12 of your notes

Detective Skills

Hypothesis

A hypothesis is an educated guess.

Conclusion

If you were able to make more observations, you would be able to form a conclusion about the events that took place.

A conclusion was the final outcome of an investigation; that is, what was found out.

i) Independent variables

An independent variable is a one whose values are chosen by the experimenter.

In other words, the values of these variables are independent of the participant's behaviour.

For the independent variable to be manipulated, at least two levels must be present in an experiment. (Refer to Story in Pg 15)

The most basic way to manipulate is by creating one experimental group (the group receiving the treatment) and a control group (exactly like the experimental group, except without the experimental treatment).

The performances of the two groups in regard to the dependent measure are then compared to assess the effect of the independent variable.

Refer to page 16 of your notes

ii) Dependent variables

The variable whose value you observe and record in experimental designs is the called the dependent variable (or dependent measure).

In other words, the dependent variable value depends on the behaviour of the participant, rather than being set by the experimenter.

iii) Constant variable

Those factors in the experiment that the scientist attempts to keep constant.

Refer to page 15 of your notes

In a Typical Lab ExpTo understand how to plan and carry out a scientific investigation, let’s try the following question:

Step 1: Observation

It is observed that ice cubes melt faster in hotter water.

Step 2: QuestionA question is asked about the observation.

“Does an ice cube melt faster in hot water?”

Step 3: Hypothesis

An ice cube would melt faster in hot water

In a Typical Lab ExpStep 4: MethodStudy all the information closely. For example, size of ice cubes, amount of water etc.

In a Typical Lab Exp(i) Variables

The independent variable is the variable that you change and this will cause the dependent variable to change and this change is being observed.

The rest of the variables that do not change are called constant variables.

In this experiment:

Independent Variable:

Dependent Variable:

Constant Variable:

Temperature of Water

Time taken by ice cube to melt completely

1) Size of Ice Cubes, 2) Size of Beaker, 3) Amount of water used

In a Typical Lab Exp(ii) Apparatus to Use

We will need these pieces of apparatus and materials;two beakers of the same size, a measuring cylinder, a stopwatch, cooler water (tap water), hot water and two ice cubes of the same size, Measuring Cylinder, ice cubes, beaker and stopwatch.

(iii) Procedure

1. Add 50 cm3 of tap water to a measuring cylinder.

2. Pour the water into a beaker3. Add one ice cube into the beaker of water4. Using the stop-watch measure the time taken

for the ice cube to melt completely.5. Repeat steps 1 to 4 for another 3 sets of

readings.

In a Typical Lab ExpStep 5: Analyse your Results

Cool Water Warm Water0

1

2

3

4

5

6

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In a Typical Lab ExpStep 6: Conclusions

From the results, we can have the following conclusion:

An ice cube melts faster in hotter water than cooler water

Refer to page 17 of your notesPierre’ 1st Experiment

Mixture of Special

Vitamins

Refer to page 17 of your notesPierre’ 2nd Experiment

Food A: Special Vitamin +

Commercial Dog Food

Collie Puppy

Food B: Another type of

Dog Food

Mutt

Refer to page 17 of your notesPierre’ 3rd Experiment

Food A: Special Vitamin +

Standard Dog Food

Beagle

Food B: Standard Dog Food

Beagle

Refer to page 17 of your notes1. What trait characterise a good scientist? How does Pierre demonstrate these traits?

A good scientist must be willing to have their own ideas questioned, must have determination and patience.

Pierre listened to his friends’ criticism on his experimentsHe showed determination by his willingness to carry on even after two failures. He showed patience as he took three long years to complete this experiment.

2. What was wrong with Pierre’s first food experiment?

Pierre did not have a control dog to compare the results with.

Refer to page 17 of your notes

3. What two mistakes did he make in his second experiment?

The two dogs are different and the commercial dog food they are given are different.

4. Why is a control important in a scientific experiment?

A control is an experimental set-up with the absence of the independent variable. This ensures that the result of the experiment is due to the independent variables and not other factors.

Refer to page 17 of your notes5. Which was the control dog and which was the experimental dog in Pierre’s third attempt?

Dog B – control dog, Dog A – experimental dog.

6. Why is repeatability important in science?

With more readings in repeated experiments, the average obtained will be more accurate and thus more reliable.

Refer to page 17 of your notes

7. What other kinds of experiments could you do to test Pierre’s conclusion about the effects of his dog vitamins?

i. Find out the difference of the height between the dogs.

ii. Create a number of tasks for the dogs to perform and see how many tests they pass

iii. Perform the experiment again on other species of dogs.