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Chemistry

SPA Tips

Over the last few days, i have received a number of emails and Facebook messages from O Level students for School-Based Science Practical Assessment (SPA) on:

  • Possible questions that may be asked in their SPA
  • Common errors that they need to be aware of in SPA

I did a check with several schools and found out that this week (9th March – 13th March) is designated as SPA Week for many schools.

SPA is considered as Paper 3 of your O Level Chemistry Examinations and involves a set of teacher-assessed practicals spread over the two/three years of your O Level course. It usually consists of a series of examinable practicals that are spread across your O Level course, with a total of 48 marks – Impt: this makes up 20% of your final O Level Chemistry Examination in terms of weightage.

Since this is a “teacher-based Science Practical Assessments”, the teacher-in-charge will assess students based on the students’ behaviours as well as their experimental techniques in the laboratory (besides your final answers in the practical sheet).

An example of a marking scheme by your teacher-in-charge based on Skill Levels 1 (Easiest) – 4 (Toughest):

Lets check out a potential question on Acids, Bases & Salts from Skill Set 1 (Easiest):

SPA Title: To prepare a soluble salt

Aim: In this experiment you will be assessed on your ability to follow instructions and use apparatus safely

Description:

A soluble crystalline salt can be prepared by the action of a suitable acid on an insoluble metallic oxide or metallic carbonate. The salt can then be purified by crystallisation.

In this experiment, copper(II) sulphate is prepared by the reaction of copper(II) carbonate on dilute sulphuric acid. The equation for this reaction is as follows:

CuCO3 (s) + H2SO4 (aq) –> CuSO4 (aq) + H2O (l) + CO2 (g)

Procedure:

  1. Measure out 30 cm3 of sulphuric acid into a beaker.
  2. Warm the acid in the beaker until the temperature of the acid is not more than 50 oC.
  3. Add the copper carbonate powder to the warm acid, a little at a time, with stirring, until all the acid is used up.
  4. Pour the mixture into the filter paper in a filter funnel. Collect the filtrate in an evaporating dish.
  5. Evaporate the filtrate. Stop heating when some crystals start to form on the surface of the filtrate or at the side of the dish.
  6. Allow the saturated solution to cool slowly.
  7. Pour off the liquid from the evaporating dish. Dry the crystals between a few sheets of filter paper.

Marking Scheme:

  • Use of appropriate measuring cylinder to measure the volume of the acid.
  • Use of appropriate apparatus (glass rod/thermometer but gently) to stir the mixture.
  • The hot mixture was poured into the filter paper without spillage/overflow.
  • The acid was allowed to cool (check that student reads the temperature of the acid before adding copper (II) carbonate).
  • Copper (II) carbonate was added into the beaker, a little at a time, with stirring and without spillage.
  • The carbonate was added until no more dissolved/no more bubbles were seen.
  • Filtration was properly done (filter paper was folded properly; no prodding of filter paper in funnel; check that filtrate is clear).
  • Flame was turned off when the filtrate was saturated (saturation: when crystals appear on the filtrate surface/at the side of the dish).
  • Proper control of the flame when filtrate was being evaporated to prevent spluttering. [Safety]
  • Goggles were worn. [Safety]

Last & Most Important Tip:

This is a “teacher-based assessment” examinations:

Students: no matter how playful you are – try NOT to STEP onto your teacher’s toe during your SPA period…ssshhhh….hope you get my hint/tip…

Parents: Do remind your child about this important point…

Teachers: Let’s help these students to have a long-lasting interest in Chemistry…

PS: Check out archives (previous blogposts) related to SPA/Chemistry Practicals HERE

PPS: Drop me a message in the “Comments Section” below. I would love to hear from you.

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