Scientific method
Science aims to develop a good explanation of natural events (phenomena) that are observed.
Scientists use the scientific method to develop explanations. This follows a specific way of working:
- propose a A starting point for investigation. An idea or explanation to be tested., which is an initial theory or explanation for an observation
- make a A suggestion, based on a hypothesis of how a factor will affect an outcome. based on the hypothesis, suggesting how changing one factor will affect the observation or outcome
- plan an experiment to test the prediction and the hypothesis on which it is based
Planning experiments
It is important to choose appropriate apparatus, materials and techniques.
A pooter is a safe way to collect insects for study
Apparatus
Containers include:
- boiling tubes
- beakers
- water baths
- sweep nets
- Device used in ecological sampling to collect insects.
Measuring apparatus include:
- timers
- rulers
- A square frame of known area used for sampling the abundance and distribution of slow or non-moving organisms.
- An instrument used to measure temperature.
- pipettes
- measuring cylinders
- microscopes
- pH meters
Biological apparatus include:
- A type of flat, circular dish with a lid. containing A gel made from algae, which provides an ideal growth medium. or other growth media
- Substance that controls the spread of bacteria in the body by killing them or stopping them reproducing. or A substance that kills or stops the growth of germs which cause disease. solutions
- food tests
- plant seedlings or lengths of pondweed
Chemicals for analysis include:
- A substance that has different colours, depending upon the pH of the solution it is in., such as A chemical solution that produces many different colour changes corresponding to different pH levels., litmus, phenolphthalein and methyl orange
- substances for chemical tests, such as Calcium hydroxide solution. It turns milky in the presence of carbon dioxide. to test for carbon dioxide, iodine solution to test for starch and A solution that can be used to test for the presence of a reducing sugar (or the presence of an aldehyde group). to test for glucose
Techniques
Standard techniques of measurement. The table gives some examples.
| Apparatus | Measures |
| Thermometer | Temperature |
| pH meter | pH |
| Timer | Time |
| Digital balance | Mass |
| Measuring cylinder | Volume of liquid |
| Burette | Volume of liquid in titration |
| Gas syringe | Volume of gas |
| Apparatus | Thermometer |
|---|---|
| Measures | Temperature |
| Apparatus | pH meter |
|---|---|
| Measures | pH |
| Apparatus | Timer |
|---|---|
| Measures | Time |
| Apparatus | Digital balance |
|---|---|
| Measures | Mass |
| Apparatus | Measuring cylinder |
|---|---|
| Measures | Volume of liquid |
| Apparatus | Burette |
|---|---|
| Measures | Volume of liquid in titration |
| Apparatus | Gas syringe |
|---|---|
| Measures | Volume of gas |
Biological experimental methods include:
- using a light microscope
- Name given to the laboratory procedures carried out to prevent the contamination of pure cultures of microorganisms. during microbiological experiments to measure the effect of antibiotics and antiseptics
- measuring increases or decreases in mass of plant tissue after The movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.
- testing the efficiency of enzymes at different temperatures or pHs
- food tests
- comparing the rate of A chemical process used by plants to make glucose and oxygen from carbon dioxide and water, using light energy. Oxygen is produced as a by-product of photosynthesis. Algae subsumed within plants and some bacteria are also photosynthetic. at different light intensities
- measuring reaction times
- determining the effect of light on plant growth
- measuring the population size of a common A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. in a A place where plants, animals and microorganisms live.
- comparing the effect of an abiotic factor on the distribution of this species