Answers to Sec 3 Sci (Chem) Discover Chemistry Workbook Page

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Blue Ink --> Teacher’s Explanation
Test for Purity
By checking melting point and boiling point
By using chromatography
To separate solvent from solution: simple
To separate mixture of miscible liquids:
fractional distillation
To separate mixture of solids by dissolving in a
solvent followed by: filtration
To separate solute from solution: evaporation
and crystallization
1. C (both the burette and pipette can measure
up to an accuracy of 0.1 cm3, both the
pipette and burette can measure 25.0 cm3)
2. A (pure substance --> fixed melting pt.)
3. B (pure substance --> fixed boiling pt.)
4. A (Air is a mixture, it contains a mixture of
5. D (Chromatography works because the
components in the mixture are soluble in the
same solvent. If they do not dissolve, they
cannot be separated because the solvent
cannot carry them across the chromatogram)
6. D (The mixture must be one soluble solid
and one insoluble solid)
7. D (Sodium Nitrate decomposes when heated
--> crystallization)
8. D (Condenser --> condense vapour to
9a) Simple distillation
9b) Evaporation to dryness
9c) Filtration
9d) Chromatography
a) Process 1: Addition of water and stirring
Purpose: To quickly dissolve the soluble sodium
b) Process 2: Filtration
Purpose: To separate the insoluble substances
from the sodium chloride solution.
c) Process 3: Evaporation
Purpose: To remove enough water from the
sodium chloride solution to form a saturated
d) Process 4: Crystallization
Purpose: To allow sodium chloride crystals
to form upon cooling.
1. D (why not A, B or C? because the delivery
tube does not extend into the liquid.)
2. A (downward delivery --> gas denser than
3. D (yellow is pure because it only contains
one spot)
3. D (copper (II) sulfate decompose when
heated --> crystallization)
5. A (crystal will form on the glass rod because it has
a cool surface and allows crystals to form)
6. B (distillation --> boiling then condensation)
7. D (cold water enters from the bottom of condenser,
distillate exits from the outlet tube of condenser)
8. B (Only the liquid can be more than 100 oC because
the vapour must be at 100 oC and the distillate will
surely be lesser than 100 oC)
9. C (Liquid X becomes darker blue because as
water is boiled and vaporized, the solution
becomes more concentrated --> Lesser and
lesser water in the solution.)
10. B (S is soluble so cannot be filtration,
cannot use chromatography because S and
water is a solution, use distillation (B)
because S and water have different boiling
points, (C) cannot separate because the
condensed water will fall back into the flask)
11a) chromatography
11b) Chlorophyll and xantophyll have different
solubility in ethanol. One solute is more
soluble in ethanol than the other, and thus, it
moves further up the filter paper.