lesson
Successful collisions require suitable energy
1 · Learn
Reaction rate depends on how often reactant particles collide successfully. Temperature, concentration, gas pressure and solid surface area can affect collision patterns. A catalyst provides an alternative pathway with lower activation energy and is not used up overall.
A catalyst does not create extra product beyond the reaction's material constraints or change an equilibrium position merely by speeding both directions. Separate rate from final amount.
2 · Worked example
Powdering a solid can increase exposed area, increasing collision opportunities under comparable conditions. It does not increase the initial mass of reactant.
3 · Your turn
Why can smaller pieces of the same total solid mass react faster?
Check your answer
They expose a larger total surface area for collisions with the other reactant.
4 · Apply your learning
Interpret supplied rate data and identify controls; no unsupervised chemical rate experiment.
Adult guidance and safety
Use supplied evidence and approved models. Practical work needs qualified supervision, risk assessment and suitable equipment. No independent chemical, mains-electricity, radiation or biological-culture experiments. Human biology is general education, not personal medical advice; do not request intimate or health disclosures.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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