Cambridge IGCSE Chemistry Past Papers

01Common mistake

Confusing Key Chemistry Terminology

Students often confuse similar chemistry terms, such as atoms, ions and molecules, elements, compounds and mixtures, or filtrate and residue. Using the wrong term can make an otherwise correct answer inaccurate

02Common mistake

Poor Description of Chemical Tests and Observations

Students often confuse an observation with a conclusion. For example, they may write “hydrogen is produced” instead of describing what they actually see, such as bubbles or effervescence.

“hydrogen is produced”

03Common mistake

Errors in Drawing Organic Structures

Students often draw incorrect numbers of bonds in organic structures, such as carbon atoms with fewer or more than four bonds or hydrogen atoms with more than one bond. Bonds such as the O–H bond in alcohols and carboxylic acids may also be missed.

04Common mistake

Failing to Balance or Properly Construct Equations

Students may leave equations unbalanced, use incorrect chemical formulae or forget that some elements exist as diatomic molecules, such as H₂, O₂ and Cl₂. They may also write a word equation when a symbol equation is requested.

05Common mistake

Vague Explanations of Kinetic Particle and Collision Theory

Students often explain changes in reaction rate without referring to particles or collisions, or confuse the arrangement, separation and movement of particles in different states of matter.

06Common mistake

Confusion Regarding Electrolysis and Redox

Students often confuse the products formed during electrolysis of molten and aqueous electrolytes, or confuse a reducing agent with the substance that is being reduced.