This document provides information on various laboratory techniques and concepts related to experimental design and chemical analysis. It discusses the following key topics in 3 sentences or less each: - Basic laboratory equipment used for carrying out reactions and storing liquids such as flasks, beakers, test tubes, and boiling tubes. - Units and methods for measuring time, temperature, mass, and volume including the SI units. Instruments like measuring cylinders and burettes used to measure volume are described. - Different methods for collecting and drying gases depending on their properties like solubility, density, and whether they are lighter or denser than air. - The difference between mixtures and solutions, and concepts like solvents, saturated solutions, and

1. Experimental techniques
and chemical analysis
Ms. Lesti

2. Welcome!
We are going to learn our
third chapter.

3. Make sure you have the
following before we start:
Notebook
Textbook
Graph paper
Pencil
Pen
ruler

4. Experimental designs
Chromatography
Separation and purifications
Contents

5. Learning outcomes
• know and understand how to
measure time, temperature, mass
and volume
• know and understand the
concept of each method of
separating mixtures
• know and understand the use of
suitable solvent, filtration,
crystallisation and distillation

6. Experimental design

7. Basic Laboratory
apparatus
• Flask are used for carrying out reactions
where fairly small amounts of liquid are
used
• Beakers are used to store liquids
temporarily or sometimes for carrying
out reactions
• Test tubes are used to carry out
reactions where small amounts of liquid
are used and not heated
• Boiling tubes are used to heat small
amounts of liquids

8. Measurement and units
Measuring
time
Measuring
temperature
Measuring
mass
The SI unit
is Kelvin.
The SI unit
is second.
The SI unit
is kilogram.

9. Measuring volumes and units
The SI unit dm3.
Beaker
• Used to estimate the volume of a
liquid, e.g. approximately 100 cm3.
Measuring cylinder
• More accurate than a beaker
• Measures up to the nearest cm3,
e.g. 99 cm3
Burette
• Accurately measures out the volume
of a liquid to the nearest ±0.1 cm3
• Scale marked (graduated) in 0.1 cm3
divisions
• Used to deliver different volumes of
liquids, e.g. 24.0 cm3 or 38.9 cm3.
Pipette
• Accurately measures out fixed
volumes of liquids, e.g. 20.0 cm3
or 25.0 cm3

13. Seatwork
Open your google classroom.
Read the measurement tools on the
worksheet.
Plot the data into graph

14. Collecting Gases and
Measuring Volume of
Gases

15. How we collect a gas depends on the
physical properties of the gas, namely:
•solubility — whether a gas is soluble in water
•density — how dense the gas is compared to air

16. Gas Solubility in water Density compared to
air
Ammonia Extremely soluble Less dense
Carbon dioxide Slightly soluble Denser
Chlorine Soluble Denser
Hydrogen Not soluble Less dense
Hydrogen chloride Very soluble Denser
Oxygen Very slightly soluble Slightly denser
Sulphur dioxide Very soluble Denser
The solubility and density of some common
gases

17. Collecting Gases –
Method 1
Displacement of water
This method is used to
collect insoluble gases.
Examples of insoluble
gases:
Hydrogen, oxygen,
carbon dioxide.

18. Collecting Gases – Method 2
Downward delivery This method is used to
collect gases that are
denser than air (and
soluble in water).
Examples of such
gases:
Chlorine, hydrogen
chloride.

19. Collecting Gases – Method 3
Upward delivery
Examples of such gases:
ammonia.
This method is used to
collect gases that are less
dense than air (and soluble
in water).

20. Learning check
Determine the method of collecting gases .
Question 2: collecting a gas that is lighter than
air
Answer 2:
Question 3: collecting a gas that is soluble
heavier than air
Answer 3:
Question 1: Measuring the volume of a gas that
is sparingly soluble in water?
Answer 1:

21. How do we collect a
dry sample
of a gas?

22. Drying a gas – method 1
Concentrated sulphuric
acid is used dry many
gases except for ammonia
Notice the positions of
the delivery tubes

23. Drying a gas – method 2
We use quicklime to
dry ammonia gas.
quicklime (calcium oxide)

24. Drying a gas – method 3
Fused calcium chloride can
be used to dry most gases.
fused calcium chloride

25. How do we measure the volume of a gas
accurately?
A gas syringe is used to measure the volume of
a gas. The gas syringe measures a maximum
volume of 100 cm3.
barrel
plunger

26. Mixtures, solutions, and
solvents

27. Mixture Solutions
solute + solvent = solution
A solution is called saturated when it can dissolve no more
solute, at that temperature.

28. Purification and
Separation

29. Pure substances and impurities
A pure substance is made up of only one substance.

30. Does purity matter?
An unwanted substance, mixed with the substance you want, is called
an impurity.
Impurities must be detected as they may cause side effects.
Impurities can be checked by its melting and boiling points.

31. A pure substance has a definite, sharp, melting point and boiling point.
When a substance contains an impurity:
– its melting point falls and its boiling point rises
– it melts and boils over a range of temperatures, not sharply.
The more impurity there is:
– the bigger the change in melting and boiling points
– the wider the temperature range over which melting and boiling occur .

33. Separation methods

36. Separating a solid from a liquid
1 By filtering

37. 2 By crystallisation
It works because soluble solids tend to be less soluble at lower temperatures.

38. 3 By evaporating all the solvent
For some substances, the solubility changes very little as the temperature falls.
So crystallisation does not work for these. Salt is an example.

39. Now you try!
Calcium carbonate is insoluble in water.
Sodium sulfate is soluble in water.
Describe how you could separate a mixture
to obtain a sample of each pure solid.

40. 4 Simple distillation
This is a way to obtain the solvent
from a solution.
Example
Water from salt solutions

41. 5 Fractional distillation
This is used to separate a mixture of liquids from each other.
Example mixture of water and ethanol

42. Copyright © 2006-2011 Marshall Cavendish
International (Singapore) Pte. Ltd.
A fractionating column, is attached to the
round-bottomed flask and the condenser for
fractional distillation.
Many glass beads in the fractionating column
provide a large surface area for vapour to
condense on.
Compare simple distillation with fractional distillation
Other than glass beads, a
fractionating column may be filled
with plates or a spiral.

43. 6 Paper chromatography
This method can be used to separate a mixture of substances. For example, you could use it to
find out how many different dyes there are in black ink:
The dyes in the ink have different solubilities in water. So they travel across the paper
at different rates. (The most soluble one travels fastest.)
That is why they separate into rings. The filter paper with the coloured rings is called a
chromatogram. (Chroma means colour.)

44. 6 Paper chromatography
Paper chromotography can also be used to identify substances
The more soluble a substance is in the solvent, the further it will
travel up the chromatography paper.

45. What are the uses of chromatography?
Chromatography is used to
• separate the components in a sample,
• identify the number of components in a sample,
• identify the components present in a sample,
• determine the purity of a sample.

46. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
How does the chromatogram of a pure substance
look like?
However, if there is only one spot on the
chromatogram, it means the substance
is pure.

47. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
What are Rf values?
The positions of
the solvent front
and spot on a
chromatogram
depend on how
long the
experiment was
allowed to run.
Chromatogram
after a period of
time.
Chromatogram
after a longer
period of time.

48. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
What are Rf values?
This ratio is called
the Rf value of the substance.
the distance travelled
by the solvent is a
constant.
The ratio between the
distance travelled by
the substance
and

49. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
Examples – notice the same Rf values
Rf = 3 cm / 4.5 cm
= 0.67
Rf = 3.5 cm / 5.2 cm
= 0.67
Chromatogram
after a period of
time.
Chromatogram
after a longer
period of time.

50. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
Rf values
The Rf value of a substance does not change as
long as chromatography is carried out under the
same conditions
(i.e. same solvent and same temperature).
This property allows us to easily identify a
substance on a chromatogram.

51. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
• Chromatography was performed on a sample of food
colouring (‘X’) and 4 banned dyes ( ‘A’, ‘B’, ‘C’ and ‘D’).
• If X contains any of the 4 banned dyes, it is not safe to
be consumed.
X A B C D
How can we identify a banned substance present
in food colouring?

52. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
- Identical dyes produce spots at the same height.
- Sample X does not contain the banned dyes A, B and D.
- However, X contains the banned dye C. Therefore, it
must not be consumed.
X A B C D
What conclusions can be drawn from this
chromatogram?

53. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
X A B C D
- Dyes A and D are pure.
- Both dye B and dye C are mixtures of two different dyes.
- Sample X is a mixture of three dyes.
What other conclusions can be drawn from this
chromatogram?

54. Copyright © 2006-2011 Marshall Cavendish International (Singapore) Pte. Ltd.
How do we identify colourless substances?
Chromatography can also be used for colourless
substances such as amino acids.
To separate and analyse colourless substances, we
apply a locating agent on a chromatogram.

55. Worksheet
Open your Google Classroom.
Answer the question on your book.