Experimental Design and Separation Techniques Flashcards
What is accuracy in an experiment?
How close the result values are to the true value
What is precision in an experiment?
How consistent (close to each other) the result values are
What does it mean if an experiment is repeatable?
It will achieve similar results if repeated with the same method.
What are control variables in an experiment?
Variables kept constant on purpose
What is the independent variable in an experiment?
The property that we change, which affects the results
What is the dependent variable in an experiment?
The property that is affected by the independent variable (the results)
What is the difference between random and systematic errors?
A random error is unpredictable; for example, a human error A systematic error is a problem with the experiment.
What is an anomaly in an experiment?
A result that doesn’t follow the pattern at all
What is the purpose of filtration?
To separate a liquid from an insoluble solid
What is the purpose of evaporation?
To separate two liquids
What is the purpose of simple distillation?
To separate a solid and a liquid (done if the liquid is required)
What is the purpose of fractional distillation?
To separate two miscible liquids
What is the purpose of chromotography?
To separate two (or more) liquids
What is the purpose of a separating funnel?
To separate two immiscible liquids
What is the purpose of filtration followed by evaporation (crystallisation)?
To separate a liquid and solid
What is the method for filtration?
- Pour the mixture into a funnel with filter paper and a beaker below
- Wait for the solution to pass through
The solid solute will stay in the filter paper (residue)
The solvent will pass through the filter paper and into the beaker (filtrate)
What is the method for evaporation?
- Pour your solution into a beaker
- Heat the solution on a hot plate until the solvent evaporates, leaving behind the solute
What is the method for simple distillation?
- Pour your solution into a distillation flask
- Heat it and measure the temperature with a thermometer
- Once the liquid solvent starts evaporating, pour cold water into the condenser, which will cool the vapor and turn it into a liquid, which will be collected in a conical flask
What is the method for fractional distillation?
- Pour your solution into a distillation flask
- Heat it and record the temperature at which the solvent starts evaporating with a thermometer
- Once the liquid solvent starts evaporating, pour cold water into the condenser, which will cool the vapor and turn it into a liquid, which will be collected in a conical flask
(Used if the boiling points of the components are close.)
What is the method for chromotography?
- Fill up a beaker to ~2cm with a solvent.
- Place the solute at 2.5cm on chromotography paper.
- Wait until the solvent reaches near the top of the paper
- Dry the chromotography paper with a hot plate or hairdryer
- Record where the different components of the solute are on the paper and calculate the Rf value.
What is the method for using a separating funnel?
- Pour a mixture into a separating funnel with the stopcock on
- Wait until the lower density liquid floats on top
- Open the stopcock and wait for the higher density liquid to drip into the beaker below.
- Close the stopcock
What is the method for filtration followed by evaporation (crystallization)?
- Put the solvent and more solute than needed in a beaker and stir with a glass rod
- Filter the mixture to remove excess solvent (use filter paper and a funnel)
- Take the filtrate and evaporate with a bunsen burner, tripod, and gauze until crystals start to form. The solution will be in an evaporating basin on top of a beaker with boiling water
- Leave the evaporating basin overnight to evaporate the rest of the water.
What is the component left in the filter paper after filtration called?
residue
What is the component in the beaker after filtration called?
filtrate
What is the liquid collected in the recieving flash during distillation called?
The distillate
How does a condenser work in distillation?
The gas goes into the condenser, and cold water is put into the pipe, and the water goes through the pipe, cooling the gas and condensing it into a liquid.
The apparatus used in distillation/fractional distillation is the same (True/False)
True
What is a pure substance?
A substance made of a single type of chemical or compound
What is a mixture?
Two or more substances mixed together but not chemically bonded, can be separated easily
What is the result of paper chromotography called?
What is the paper called after the experiment?
chromatogram
What is the solvent front in chromotography?
How far the solvent traveled No component travels further than it.
What is the Rf Value in chromotography?
How soluble a component of a solution is based on how far it moved on the chromotography paper
How is the Rf value calculated?
Distance travelled by component / Distance travelled by solvent
