C2 - Experimental techniques Flashcards
Which piece of equipment is used to measure time and what are the units? [2]
Stopwatch in seconds
Which piece of equipment is used to measure temperature and what are the units? [2]
Thermometer in degrees celsius
Which piece of equipment is used to measure mass and what are the units? [2]
Mass balance in grams
Which 3 pieces of equipment are used to measure volume of a liquid and what are the units? [4]
Measuring cylinder, volumetric pipette and burette in cm³
Which piece of equipment is used to measure volume of a gas and what are the units? [2]
Gas syringe in cm³
What process is used to separate two or more solids that are soluble? [1]
Paper chromatography
How do you calculate Rf values in paper chromatography? [1]
Distance moved by solute ÷ Distance moved by solvent
Define a pure substance [1]
A substance that contains a single element or compound not mixed with any other substance
Describe 3 ways that the purity of a substance can be assessed [3]
Melting point, boiling point, chromatography
Describe how melting point / boiling point can be used to assess purity [2]
A pure substance will have a sharp melting / boiling point. An impure substance will melt over a temperature range
Describe how chromatography can be used to assess purity [1]
A pure substance will produce only one well defined spot on a chromatogram
Describe how to obtain a pure, dry sample of a substance from a chromatogram [3]
Isolate the substance, dissolve in solvent, evaporate the solvent
Describe two examples of where purity of substances is important [2]
Manufacture of compounds used in drugs and food additives
What is a solvent? [1]
A substance that dissolves a solute
What is a solute? [1]
A substance that is dissolved in a solvent?
What is a solution? [1]
A liquid mixture composed of two or more substances
Define volatility [1]
How easily a substance evaporates / changes from a liquid to a gas
Define solubility [1]
How easily a substance dissolves
What is filtration used for? [1]
To separate an insoluble solid from a liquid
What is the filtrate in filtration? [1]
The liquid or solution that has passed through the filter
What is crystallisation? [1]
When a liquid that contains a dissolved salt is evaporated to leave the salt behind
What is distillation used for? [1]
To separate a solvent from a solution
What is the difference between immiscible and miscible liquids? [2]
Immiscible liquids don’t mix, miscible liquids do mix
How can immiscible liquids be separated? [1]
By using a separating funnel
Why can fractional distillation be used to separate miscible liquids / gases? [1]
Because the liquids / gases have different boiling points
What is a residue in filtration? [1]
A substance that remains after evaporation, distillation, filtration or similar process
