The introduction is the what and why of the experiment, and show answer the following questions:
What was the purpose or objective of the experiment/research?
Why was the experiment/research conducted in a particular manner?
Why was it important in a broader context?
The purpose of the introduction is to put the reader in the picture and place the research/experiment within a context.
The following may be included in the Introduction:
Background information about the experiment to be carried out
A brief review of previous research (relevant literature) to give a background - paraphrase relevant facts from the scientific literature, citing the source to support each statement
Reason/s why the research was undertaken
The introduction should not include any results or conclusions.
Example:
Photosynthesis is a vital process for life. It occurs when plants intake carbon dioxide, water, and light, and results in the production of glucose and water. The light required for photosynthesis is absorbed by chlorophyll, the green pigment of plants, which is contained in the chloroplasts.
The word equation for photosynthesis is water + carbon dioxide --> glucose + oxygen (note: This process can only occur in the presence of sunlight and chlorophyll)
The glucose produced through photosynthesis is stored as starch, which is used as an energy source for the plant and its consumers. The presence of starch in the leaves of a plant indicates that photosynthesis has occurred
A study conducted by Mengel and Judel (2006) on the "Effects of light intensity on the activity of starch synthesising enzymes and starch synthesis in developing wheat grains" found that " ... reducing light intensity (shading) during the grain filling period depressed grain growth and starch production by about 20%"
By increasing the amount of sunlight exposure to plants (if water and carbon dioxide are also present), scientists may be able to increase amount of glucose being produced (which will result in more starch being formed)
Iodine solution is often used to test leaves for the presence of starch. Iodine solution has the ability to penetrate the cell walls of plants and react with any starch present. This results in a physical colour change from brown to a black-blue colour in the presence of starch