Scientific method
Science aims to develop a good explanation of natural events (phenomena) that are observed.
Scientists develop explanations using the scientific method. This follows a specific way of working:
- propose a A starting point for investigation. An idea or explanation to be tested., 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 outcome
- Plan an experiment - this should test the prediction and the hypothesis on which it is based
Planning experiments
It is important to choose appropriate apparatus, materials and techniques.
An example of equipment that could be used in an experiment
Apparatus
Containers including:
- test tubes
- boiling tubes
- beakers
- flasks
Measuring apparatus including:
- timers
- rulers
- An instrument used to measure temperature.
- Long glass tube with a tap and marked with volume measurements, used in titrations.
- pipettes
- measuring cylinders
Heating and electrical apparatus including:
- Bunsen burners
- electric heating mantle
- water bath
- power pack
- leads, crocodile clips and electrodes
Chemicals
Reacting chemicals including:
- The substance formed when the hydrogen ion in an acid is replaced by a metal ion.
- Corrosive substance which has a pH lower than 7. Acidity is caused by a high concentration of hydrogen ions.
- A base which is soluble in water.
- Shiny element that is a good conductor of electricity and heat, and which forms basic oxides.
- Compounds that contain carbon atoms, joined by covalent bonds to other atoms (including other carbon atoms)., including Saturated hydrocarbon. A compound of hydrogen and carbon only, with no C=C bonds., Unsaturated hydrocarbon with a double bond between the carbon atoms. and An organic compound containing a hydroxyl group, -OH. The 'alcohol' in alcoholic drinks is ethanol, produced by the fermentation of sugars and found in wines, spirits and beers.
- water
Chemicals for analysis including:
- 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., silver nitrate Mixture formed by a solute and a solvent. and barium chloride solution
- The liquid in which the solute dissolves to form a solution. for Chromatography is used to separate different substances dissolved in a liquid.
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 |
Methods of analysis including
- chromatography
- A qualitative identification technique where samples are heated and the metal ions present are identified by characteristic flame colours. to identify metal Electrically charged particle, formed when an atom or molecule gains or loses electrons.
- chemical tests to identify gases or ions
- titration
Methods for carrying out reactions including:
- test tube reactions
- heating methods, such as Bunsen burner, electric heating mantle, water bath
- The decomposition (breakdown) of a compound using an electric current.