Experimental Design and Separation Techniques

Question 1

What is accuracy in an experiment?

Answer 1

How close the result values are to the true value

Question 2

What is precision in an experiment?

Answer 2

How consistent (close to each other) the result values are

Question 3

What does it mean if an experiment is repeatable?

Answer 3

It will achieve similar results if repeated with the same method.

Question 4

What are control variables in an experiment?

Answer 4

Variables kept constant on purpose

Question 5

What is the independent variable in an experiment?

Answer 5

The property that we change, which affects the results

Question 6

What is the dependent variable in an experiment?

Answer 6

The property that is affected by the independent variable (the results)

Question 7

What is the difference between random and systematic errors?

Answer 7

A random error is unpredictable; for example, a human error A systematic error is a problem with the experiment.

Question 8

What is an anomaly in an experiment?

Answer 8

A result that doesn’t follow the pattern at all

Question 9

What is the purpose of filtration?

Answer 9

To separate a liquid from an insoluble solid

Question 10

What is the purpose of evaporation?

Answer 10

To separate two liquids

Question 11

What is the purpose of simple distillation?

Answer 11

To separate a solid and a liquid (done if the liquid is required)

Question 12

What is the purpose of fractional distillation?

Answer 12

To separate two miscible liquids

Question 13

What is the purpose of chromotography?

Answer 13

To separate two (or more) liquids

Question 14

What is the purpose of a separating funnel?

Answer 14

To separate two immiscible liquids

Question 15

What is the purpose of filtration followed by evaporation (crystallisation)?

Answer 15

To separate a liquid and solid

Question 16

What is the method for filtration?

Answer 16

1. Pour the mixture into a funnel with filter paper and a beaker below
2. 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)

Question 17

What is the method for evaporation?

Answer 17

1. Pour your solution into a beaker
2. Heat the solution on a hot plate until the solvent evaporates, leaving behind the solute

Question 18

What is the method for simple distillation?

Answer 18

1. Pour your solution into a distillation flask
2. Heat it and measure the temperature with a thermometer
3. 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

Question 19

What is the method for fractional distillation?

Answer 19

1. Pour your solution into a distillation flask
2. Heat it and record the temperature at which the solvent starts evaporating with a thermometer
3. 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.)

Question 20

What is the method for chromotography?

Answer 20

1. Fill up a beaker to ~2cm with a solvent.
2. Place the solute at 2.5cm on chromotography paper.
3. Wait until the solvent reaches near the top of the paper
4. Dry the chromotography paper with a hot plate or hairdryer
5. Record where the different components of the solute are on the paper and calculate the Rf value.

Question 21

What is the method for using a separating funnel?

Answer 21

1. Pour a mixture into a separating funnel with the stopcock on
2. Wait until the lower density liquid floats on top
3. Open the stopcock and wait for the higher density liquid to drip into the beaker below.
4. Close the stopcock

Question 22

What is the method for filtration followed by evaporation (crystallization)?

Answer 22

1. Put the solvent and more solute than needed in a beaker and stir with a glass rod
2. Filter the mixture to remove excess solvent (use filter paper and a funnel)
3. 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
4. Leave the evaporating basin overnight to evaporate the rest of the water.

Question 23

What is the component left in the filter paper after filtration called?

Answer 23

residue

Question 24

What is the component in the beaker after filtration called?

Answer 24

filtrate

Question 25

What is the liquid collected in the recieving flash during distillation called?

Answer 25

The distillate

Question 26

How does a condenser work in distillation?

Answer 26

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.

Question 27

The apparatus used in distillation/fractional distillation is the same (True/False)

Answer 27

True

Question 28

What is a pure substance?

Answer 28

A substance made of a single type of chemical or compound

Question 29

What is a mixture?

Answer 29

Two or more substances mixed together but not chemically bonded, can be separated easily

Question 30

What is the result of paper chromotography called?

What is the paper called after the experiment?

Answer 30

chromatogram

Question 31

What is the solvent front in chromotography?

Answer 31

How far the solvent traveled No component travels further than it.

Question 32

What is the Rf Value in chromotography?

Answer 32

How soluble a component of a solution is based on how far it moved on the chromotography paper

Question 33

How is the Rf value calculated?

Answer 33

Distance travelled by component / Distance travelled by solvent