Experimental Techniques Flashcards
Apparatus for measuring time
Digital stop watch (0.01s)
Apparatus for measuring temperature
Mercury in glass thermometer (degree celsius)
Apparatus for measuring mass
Electric top pan balance (0.01g)
Apparatus for measuring volume
- Beaker: Used to estimate liquid volume
- Measuring cylinder (0.1cm3): More accurate than beaker
- Pipette (0.1cm3): Measures fixed volumes of liquids accurately
- Burette (0.1cm3): Used for measuring variable volumes of liquids accurately
Paper Chromatography
It is a separation technique that is used to separate and identify the components in a mixture
Colourless substances can be made visible by spraying the chromatogram with
Locating agent
Retardation factors (Rf value)
Rf Value = Distance traveled by spot / Distance traveled by solvent
Methods used to separate an insoluble solid from a liquid
Filtration, centrifugation and decantation
Process of filtration
Filtration is carried out by pouring the mixture into a funnel covered by a filter paper. Whilst the liquid will pass through the filter, solids will get caught, thereby separating them.
Process of Decantation
Decanting is the simple process of letting insoluble solids settle in the liquid before gently pouring it out later.
Process of Centrifugation
Centrifuging is a technique which uses a spinning tube. The spinning generates a strong centripetal force which causes denser materials (i.e. solids) to travel towards the bottom of the centrifuge tube at a faster rate than normal gravity.
Evaporation
This is a simple process of separating the crystals of a solute from a solution. Simply let the solvent evaporate off and it will leave the solids behind.
Crystallization
This technique is used to separate two soluble solids from a solution (given that they have different solubilities). It works by dissolving the two solids in minimal water, and then slowly cooling it. The less soluble salt will crystallize first.
Simple distillation
This method is used to separate a volatile liquid (easy to evaporate) from a solution with a non-volatile solid. For example, salt water can be purified using this method.
Fractional distillation
This method is used to separate the different liquids from a liquid mixture. For example, a mixture of water and ethanol can be separated using this method.
