Ch21 Experimental Design and Separation Techniques Flashcards
Define accuracy:
How close the value is to the true value
Define precision:
The degree to which repeat measurements are considered (close to each other)
Define resolution:
The smallest division on the instrument
Example this could be 1mm on a ruler or 0.1g on a balance
Define calibration:
The process of checking that the device gives accurate values by using it to read samples with known values
Define repeatability:
Where an experiment (or series of experiments) can be repeated using the same method and obtain reproducible (similar) results
Define control variable:
A variable that is kept the same during an investigation
Define independent variable:
The variable that is altered during a scientific investigation
Define dependent variable:
the variable that is measured during a scientific investigation
Define random errors:
These are unpredictable variations in results caused by factors such as human errors
Define systematic errors:
These are consistent errors that may arise because of a problem with the experimental design/in a piece of equipment being used
Define anomalous:
Something that is unusual or unexpected and deviates from the normal
One of a series of repeated experimental results that is much larger/smaller than the others is a anomalous result
Define zero error:
A type of systematic error in a measuring instrument
Example the reading on a balance may not reset to zero when there is nothing on the balance
Define filtration:
The separation of a solid from a liquid, using a fine filter paper, which does not allow the solid to pass through
Define crystallization:
The process of forming crystals from a saturated solution
Define simple distillation:
A distillation method for separating the liquid solvent from a solution containing dissolved solids
Define fractional distillation:
A method of distillation using a fractionating column, used to separate liquids with different boiling points
Define chromatography:
A technique employed for the separation of mixtures of dissolved substances, which was originally used to separate colored dyes
Define solution:
Formed when a substance (solute) dissolves into another substance (solvent)
Define residue:
The solid left behind in the filter paper after filtration has taken place
Define filtrate:
The liquid that passes through the filter paper during filtration
Define anti-bumping granules:
Small granules that help produce the size of bubbles formed when a liquid boils
Used for safety to stop the flask shaking
Define distillate:
The liquid collected in the receiving flask during distillation
Define desalination:
The removal of dissolved salts and minerals from seawater to produce drinking water
Define pure substances:
A single chemical element/compound
It melts and boils at definite temperatures
Define mixture:
2/more substances mixed together, but not chemically combined
The substances can be separated by physical means
Define paper chromatography:
A simple type of chromatography used to separate the components of soluble substances based on their rate of migration in a solvent (mobile phase) on sheets of filter paper (stationary phase)
Define define solvent front:
The moving boundary of the liquid solvent that moves up the paper during chromatography
Define chromatogram:
The result of a paper chromatography run, showing where the spots of the samples have moved to
Define Rf value:
In chromatography, the ratio of the distance traveled by the solute, to the distance traveled by the solvent front
Define locating agent:
A compound that reacts with invisible, colourless spots, separated by chromatography to produce a colored product that can be seen
