Guide to Writing Good Observations in Chemistry Practical

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

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Front (Question)

Adding solutions how to record observation? (2pt)

Back (Answer)

(i) colour of precipitate (i) A ……… (colour) ppt is formed. (ii) colour change in solution (ii) ………… (initial colour) solution turned ………… (final colour).

Front (Question)

Adding solutions (i) colour of precipitate

Back (Answer)

(i) A ……… (colour) ppt is formed.

Front (Question)

Adding solutions (ii) colour change in solution

Back (Answer)

(ii) ………… (initial colour) solution turned ………… (final colour).

Front (Question)

Heating of solid how to record observations? (4pt)

Back (Answer)

(i) change in colour of solid (before and after heating) (i) The green powder decomposes to form a black solid. (ii) change of state (ii) Solid Y melts to form a yellow liquid (not solution). (iii) colour of residue on cooling (may be different when hot) (iii) A white residue remains. (iv) Observation for gas (if any) (iv) ………….. (colour) ………….. (smell) gas evolved. (Refer to Test for gas)

Front (Question)

Heating of Solid (i) change in colour of solid (before and after heating)

Back (Answer)

(i) The green powder decomposes to form a black solid.

Front (Question)

Heating of Solid (ii) change of state

Back (Answer)

(ii) Solid Y melts to form a yellow liquid (not solution).

Front (Question)

Heating of Solid (iii) colour of residue on cooling (may be different when hot)

Back (Answer)

(iii) A white residue remains.

Front (Question)

Heating of Solid (iv) Observation for gas (if any)

Back (Answer)

(iv) ………….. (colour) ………….. (smell) gas evolved. (Refer to Test for gas) CO2 Bubble gas into limewater, a white precipitate will form if CO2 is present Hydrogen gas Hold lighted splint near edge of tube, if hydrogen is present, the splint will extinguish with a ‘pop’ sound

Front (Question)

Test for gas - CO2

Back (Answer)

Bubble gas into limewater, a white precipitate will form if CO2 is present

#10

Front (Question)

Test for gas - Hydrogen gas

Back (Answer)

Hold lighted splint near edge of tube, if hydrogen is present, the splint will extinguish with a ‘pop’ sound

#11

Front (Question)

Test for gas How to record observations? (4pt)

Back (Answer)

• Effervescence • Colour of gas • Smell of gas • Specific test for gas Effervescence of colourless and odourless gas is observed. Gas extinguished a lighted splint with a ‘pop’ sound. Gas formed white ppt when bubbled into limewater.

#12

Front (Question)

Test for gas Effervescence

Back (Answer)

Effervescence of colourless and odourless gas is observed. (bubbling)

#13

Front (Question)

Adding solid to solutions How to write observations (2pt)?

Back (Answer)

• solubility of solid in water • colour of the solution formed ……….. (colour) solid dissolves to form a ………….. (colour) solution. OR ……….. (colour) solid remained insoluble.

#14

Front (Question)

Using Universal Indicator How to write observation? (1pt)

Back (Answer)

• colour change of Universal Indicator Green Universal Indicator turns ………… (final colour). Inference: Mixture is acidic/neutral/alkaline

#15

Front (Question)

Using Univerrsal Indicator Color change of universal indicator 2pt

Back (Answer)

Green Universal Indicator turns ………… (final colour). Inference: Mixture is acidic/neutral/alkaline

#16

Front (Question)

Using litmus paper How to write observation

Back (Answer)

• colour change of litmus paper Red/blue litmus paper remained red/blue OR turned blue/red. Red litmus paper = acidic, Blue litmus paper = alkaline, remained same colour = neutral, no effect

#17

Front (Question)

When filtering a solution/suspension How to write observation? (2pt)

Back (Answer)

• Colour of residue The residue is a ………… (colour) solid. • Colour of filtrate The filtrate is a colourless solution or ………… (colour) solution.

#18

Front (Question)

When filtering a solution/suspension * Colour of residue

Back (Answer)

The residue is a ………… (colour) solid.

#19

Front (Question)

When filtering a solution/suspension * Colour of filtrate

Back (Answer)

The filtrate is a colourless solution or ………… (colour) solution.

#20

Front (Question)

Reactions with Acids 2cm3 of dilute hydrochloric acid added to 2cm3 of dilute sodium hydroxide Observation (2pt)

Back (Answer)

Solution remains colourless/No visible change; Test-tube feels warm (Deduction: Thermal energy given out)

#21

Front (Question)

Reactions with Acids 2cm3 of dilute hydrochloric acid added to one magnesium ribbon Observations (4pt)

Back (Answer)

Effervescence of a colourless, odourless gas is observed and; Gas extinguished a lighted splint with a ‘pop’ sound; The magnesium ribbon becomes smaller gradually; Colourless solution is formed;

#22

Front (Question)

Reactions with Acids 2cm3 of dilute hydrochloric acid added to calcium carbonate Observations (4pt)

Back (Answer)

Effervescence of colourless and odourless gas is observed; Gas formed white ppt when bubbled into limewater. Colourless solution is formed; White solid partially dissolves to form a colourless solution.

#23

Front (Question)

Reactions with Acids 2cm3 of dilute hydrochloric acid added to 2cm3 of dilute sodium hydroxide Chemical Equation + Type of reaction?

Back (Answer)

HCl(aq)+ NaOH(aq) –> NaCl(aq) + H2O(l) Type of reaction: Neutralisation NaCl is a salt hence Na+ is a cation and Cl- is an anion

#24

Front (Question)

Reactions with Acids 2cm3 of dilute hydrochloric acid added to one magnesium ribbon Deduction of gas produced Chemical Equation + Type of reaction

Back (Answer)

Hydrogen 2HCl(aq)+ Mg(s) –> MgCl2(aq) + H2(g) Type of reaction: Acid-metal reaction MgCl2 is a salt where Mg2+ is a cation and Cl- is an anion.