Reaction profiles
Particles react only when they collide with enough energy .
The minimum energy needed for a reaction to happen is the activation
energy
A reaction profile shows the energy of the reactants and products
and the path between them, with a curve rising to a peak and falling again
The activation energy is the gap from the reactants up to the top
of the curve . The overall energy change is the gap from the
reactants to the products
Exothermic
Endothermic
Products compared with reactants lower in energy
higher in energy
Energy change arrow points down
points up
Surroundings get warmer
get cooler
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Reaction profiles progress of reaction energy reactants products activation energy overall energy change exothermic products are LOWER than reactants energy is given out — the surroundings heat up progress of reaction energy reactants products activation energy overall energy change endothermic products are HIGHER than reactants energy is taken in — the surroundings cool down Breaking bonds is endothermic and making bonds is exothermic. If more energy is released making bonds than is used breaking them, the reaction is exothermic overall. Two reaction profiles side by side: exothermic with products below reactants, endothermic with products above, each with a curved path, the activation energy arrow from reactants to the peak, and the overall energy change arrow between reactants and products, all labelled
Draw the profile with a ruler for the levels and arrows. Label
the activation energy as the arrow from reactants to the peak , not
the peak itself
The energy levels are energy , not temperature or heat. A profile
showing "heat of reactants" is marked down
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In the full topic
• Reaction profiles• Bond energies [Higher Tier]Read the free chemistry topics →