Common Mistakes to Avoid (Copy)

Mistake	Why It’s Wrong	Correct Way
Using pen or colored pencil	Not permitted — must be pencil-only	Always use a sharp HB pencil
Sketchy or double lines	Looks untidy and unclear	Draw single, clean lines
Overlapping or crooked labels	Confuses examiner	Draw horizontal, ruler-drawn label lines
Using arrowheads on labels	Not accepted in ATP papers	Straight lines only, no arrows
Incorrect scale or proportions	Unrealistic, loses clarity	Keep realistic relative sizes (e.g. burette longer than pipette)
Missing critical apparatus (e.g. thermometer in distillation)	Loses major marks	Learn full standard setup for each experiment
No direction for water in condenser	Examiner assumes lack of understanding	Always label “water in (bottom)”, “water out (top)”
Bunsen burner flame drawn too close to glassware	Can break test tube in real life	Heat at the base, not directly on test tube wall

Mistake	Why It’s Wrong	Correct Way
Axes not labeled with units	Marks lost for missing detail	Write both quantity and unit (e.g., Time / s)
Irregular or broken scale	Misrepresents data	Use a uniform scale with equal gaps
Using bar chart for continuous data	Scientifically inaccurate	Use line graph for temp/time type data
Not using full graph space	Reduces precision	Scale to at least 75% of grid
Plotting error or missing data points	Reduces accuracy and interpretation	Always double-check points before drawing
Forgetting to mark solvent front in chromatography	Key part of analysis	Draw and label solvent front at top of paper strip
Baseline drawn in pen for chromatography	Affects separation	Always draw baseline in pencil

Mistake	Why It’s Wrong	Correct Way
Not identifying all variables	Incomplete plan	State independent, dependent, and at least two control variables
No mention of repetition	Reduces reliability	Always say “repeat to improve reliability”
Forgetting measurements or quantities	Makes the method vague	Include specific volumes, times, or masses
Using vague terms: “add stuff”, “test the thing”	Unscientific language	Use terms like “add 5 cm³ of dilute HCl using a pipette”
Not stating observable changes	Can’t be marked if nothing is observed	Write “observe color change/gas formation/temperature rise”

Mistake	Why It’s Wrong	Correct Way
Saying “a reaction happened”	Too vague	State observable results: fizzing, color change, ppt formation
Incorrect color description	Loses marks	Learn standard color changes, e.g.:

Copper(II) carbonate → black (on heating)
Benedict’s test → red-orange ppt
Litmus: red in acid, blue in alkali |
| Writing gas names without tests | Can’t confirm identity | Always describe the test:
O₂ relights glowing splint
H₂ pops with lighted splint
CO₂ turns limewater milky |
| Wrong test for substance | Wrong method = zero marks | Learn correct test-reagent pairs:
Cl⁻ → silver nitrate + nitric acid
SO₄²⁻ → barium chloride + HCl
NH₄⁺ → warm with NaOH → turns red litmus blue (due to NH₃) |

Mistake	Why It’s Wrong	Correct Way
Ignoring the units in data tables	Leads to wrong graph/data interpretation	Check if values are in cm³, dm³, g, mol
Mixing up dependent and independent variables	Affects design and axis labeling	Independent = what you change
Dependent = what you measure
Describing how the result “should” look	Examiner wants observed data, not theory	Say what you saw, not what you expected
Forgetting safety precautions when asked	Part of the marking	Always mention:

Mistake	Why It’s Wrong	Correct Way
Saying “some stuff was added”	Informal	Say “add 5 cm³ of sodium thiosulfate solution”
Writing in first person (“I added…”)	Not exam-appropriate	Use passive voice: “5 cm³ was added”
Using general terms like “chemical” or “substance”	Doesn’t show knowledge	Always name the chemicals used
Repeating the question in the answer	Wastes time and space	Directly answer with specific points

Mistake	Why It’s Wrong	Correct Way
Leaving diagrams unlabelled	Major marks lost	Always label every part of the setup
Not checking for missing units in answers	Incomplete response	Every calculation must have units
Not reviewing calculations	Risk of arithmetic errors	Quickly recheck math before moving on
Answering with theory when observation is asked	Misreads the command word	Observe = describe what you see,
Explain = use chemistry theory

Trap	Tip to Avoid
“What color change did you see?” → writing the reason for color change instead	Always read if the question asks for observation or explanation
Thinking a solid dissolving is a chemical reaction	Check if there’s new substance formed (gas, precipitate, etc.)
Using the wrong collection method for a gas	Know the 3 methods: over water, upward, downward delivery based on density and solubility

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