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GCSE Chemistry · key term
A relationship in which two quantities change by the same factor, so their ratio remains constant.
Used by Edexcel and OCR
Paper 2
A relationship in which multiplying one quantity by a factor multiplies the other by the same factor.
Revise: Mathematical ApplicationsDirect proportion is a stronger claim than ‘increases’. If doubling a factor doubles the rate, and tripling it triples the rate under the same conditions, the data support direct proportion. A graph of rate against that factor would be a straight line through the origin.
Specification CM5.2iv, CM6.1iv · Paper 2 (Foundation), Paper 4 (Higher)
Revise: Proportionality in RatesA straight line that does not pass through the origin is not evidence of direct proportion. Nor is a curved graph. In both cases, increasing the factor may still increase the rate, but not in a constant proportion.
A relationship in which one quantity is always a constant multiple of another, so is constant and .
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A relationship in which two quantities change by the same multiplication factor, so their ratio remains constant.
Revise: ProportionalityThese particular illustrative results therefore show direct proportion.
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