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SingaporeChemistry

Energetics, Rates of Reaction and Redox

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How does a catalyst speed up a reaction without being used up, and how is the rate measured and graphed?

Explain the action of a catalyst in lowering activation energy, describe enzymes as biological catalysts, and interpret rate graphs of product formed against time
A focused answer to the O-Level Chemistry outcome on catalysts and rate graphs. How a catalyst lowers activation energy without being used up, enzymes as biological catalysts, and reading the shape of a rate graph of product against time.
8 min answer →

Why do some reactions give out heat and others take it in, and how is this shown on an energy profile?

Distinguish exothermic and endothermic reactions by energy change, draw and interpret energy profile diagrams, and explain energy change in terms of bond breaking and bond forming
A focused answer to the O-Level Chemistry outcome on energetics. Telling apart exothermic and endothermic reactions, drawing energy profile diagrams, and explaining the overall energy change through bond breaking and bond forming.
8 min answer →

What is redox in terms of oxygen and electrons, and how are oxidising and reducing agents identified?

Define oxidation and reduction in terms of oxygen and electron transfer, identify oxidising and reducing agents, and use colour changes of common reagents to test for them
A focused answer to the O-Level Chemistry outcome on redox. Oxidation and reduction defined by oxygen and by electron transfer, identifying oxidising and reducing agents, and the colour-change tests that detect them.
8 min answer →

What factors change the speed of a chemical reaction, and how does collision theory explain them?

Describe the effect of concentration, pressure, surface area and temperature on the rate of reaction, and explain these effects using collision theory
A focused answer to the O-Level Chemistry outcome on reaction rate. How concentration, pressure, surface area and temperature change the speed of a reaction, and the collision-theory explanation in terms of frequency and energy of collisions.
9 min answer →