The Scientific Method

Galileo Galilei is attributed as the father of modern science. The video in the link below details his life and contributions.

(Credits: The Biographics youtube channel)

Galileo’s methodology involved three (3) steps:

1. Intuition - observing a certain phenomenon in the natural world and identifying the parts which can be translated into mathematical form
2. Demonstration - deductive demonstration by pure mathematics; must be true of similar instances of the phenomenon
3. Experimentation - verifying these deductions via experiments

Our modern scientific methodology usually employs the following steps:

1. Observe natural phenomena
2. Formulate an hypothesis to explain the phenomena
3. Use the hypothesis to predict effects
4. Perform experiments to test if the predicted effects happen

Variables

Variables are properties that can change in value (they can vary) for example:

• temperature of a gas
• time taken to eat a serving of fries
• volume of a ball

Constants, on other hand, cannot change in value.

Physical quantities can serve as variables in our experiments.

Types of variables

There are three (3) types of variables:

1. Independent/Manipulated variables are variables whose values we choose to change/manipulate
2. Dependent/Responding variables are variables whose values change as a result of/in response to us changing the value of the manipulated variable
3. Controlled variables are variables whose values we choose to keep fixed. These are NOT constants. They are still variables because their value can be changed but we choose not to change them. This is because they may affect the value of the other variables (manipulated and responding)

Example 1: Using different liquids to water a plant

Plan and design an experiment to see which of three liquids (water, orange juice and soda) will make a plant grow fastest.

1. Manipulated variable: The type of liquid used to water the plants (water vs. orange juice vs. soda)
2. Responding variable: The growth rate of the plant OR the surface area of the leaves OR the the length of the stem
3. Controlled variable(s): amount of each liquid used on the plants (e.g. 100 ml), observation period of each plant (e.g. for 1 week), starting age of the plants (e.g. 1 week-old seedlings), type of soil (e.g. clayey), the type of plant (e.g. black-eye pea)

Notice that any of the controlled variables could have been used as a manipulated variable in another experiment

Example 2: The effect of the presence of light on fruit ripening

Plan and design an experiment to determine if it is better to store fruits in a dark area or a lit area to speed up ripening.

1. Manipulated variable: the amount of light the fruits are exposed to (0 hours of sunlight vs. 3 hours of sunlight daily) OR the location of storage (lit area vs. dark area)
2. Responding variable: the rate of ripening OR the time taken to become a certain colour
3. Controlled variable(s): temperature at which the fruits are stored, humidity of the environment, shelf-life of the fruit, interval at which the ripening is checked

Example 3: The effect of the frequency of drinking water on the happiness level of children

Plan and design an experiment to determine if a higher frequency of drinking water makes children happier.

1. Manipulated variable: how often we give water to the children (the frequency of drinking)
2. Responding variable: the happiness level of the children
3. Controlled variable(s): amount of water given each time (e.g. 1 cup), the type of water given (e.g. spring water), temperature of water (e.g. room temperature), the age range of the children (e.g. 9-10 year olds), the colour of the container used (e.g. clear)