Class 9 common misconceptions

Does the order of coordinates matter? — Tempting mistake: “(2, 5) and (5, 2) give the same point.”

1 worked visual example · 8 “If your child says…” checks

Can a variable in a denominator be linear? — Tempting mistake: “1/x + 2 is a linear polynomial.”

1 worked visual example · 6 “If your child says…” checks

Can a calculator's finite display prove a number is rational? — Tempting mistake: “√2 is rational because a calculator displays 1.414213562, a terminating decimal.”

1 worked visual example · 8 “If your child says…” checks

Does expanding a product mean multiplying only matching terms? — Tempting mistake: “(x + 2)(x + 3) = x² + 6”

1 worked visual example · 8 “If your child says…” checks

Does every chord cross the centre? — Tempting mistake: “A chord must go through the centre of a circle.”

1 worked visual example · 8 “If your child says…” checks

What happens to area when lengths double? — Tempting mistake: “Doubling all side lengths doubles the area.”

1 worked visual example · 8 “If your child says…” checks

Is every named outcome equally likely? — Tempting mistake: “A spinner with red and blue has a ½ chance of red.”

1 worked visual example · 8 “If your child says…” checks

Does an increasing sequence always add the same number? — Tempting mistake: “2, 4, 8, 16 is arithmetic because every term is larger than the previous one.”

1 worked visual example · 8 “If your child says…” checks

Can one seedling per group settle an experiment? — Tempting mistake: “Fertiliser makes seedlings grow faster because my one fertilised seedling grew more than my one untreated seedling.”

1 worked visual example · 7 “If your child says…” checks

Do plant cells have cell membranes? — Tempting mistake: “Plant cells have walls in place of membranes.”

1 worked visual example · 8 “If your child says…” checks

Do all cells in a tissue have the same shape? — Tempting mistake: “A tissue can contain only one cell shape.”

1 worked visual example · 8 “If your child says…” checks

Can displacement be zero after travelling? — Tempting mistake: “A runner who travels 400 m must be 400 m from the start.”

1 worked visual example · 8 “If your child says…” checks

Does clear water have to be pure? — Tempting mistake: “A clear liquid must be pure water.”

1 worked visual example · 8 “If your child says…” checks

Does constant motion require a net force? — Tempting mistake: “A trolley moving steadily must have a forward net force.”

1 worked visual example · 8 “If your child says…” checks

Does holding a heavy load do mechanical work on it? — Tempting mistake: “I do mechanical work on a bag because my arms get tired while I hold it still.”

1 worked visual example · 6 “If your child says…” checks

Does losing an electron change the element? — Tempting mistake: “A sodium atom becomes a different element when it loses an electron.”

1 worked visual example · 8 “If your child says…” checks

Can you change subscripts to balance an equation? — Tempting mistake: “Change H₂O to H₂O₂ to balance the oxygen atoms.”

1 worked visual example · 8 “If your child says…” checks

Do air particles travel all the way from speaker to listener? — Tempting mistake: “The speaker sends its air particles across the room.”

1 worked visual example · 8 “If your child says…” checks

Can reproduction happen with one parent? — Tempting mistake: “Every living thing needs two parents to reproduce.”

1 worked visual example · 7 “If your child says…” checks

Does a similar habitat mean close classification? — Tempting mistake: “A dolphin and a shark belong to the same group because both swim.”

1 worked visual example · 8 “If your child says…” checks

Does energy cycle through ecosystems like matter? — Tempting mistake: “Energy comes back to producers as dead material breaks down.”

1 worked visual example · 6 “If your child says…” checks