Temperature and activation energy
| English | Chinese | Pinyin |
|---|---|---|
| activation energy | 活化能 | huó huà néng |
| Boltzmann distribution | 玻尔兹曼分布 | bō ěr zī màn fēn bù |
Why heat speeds things up
- The activation energy 活化能 ($E_A$) is the minimum energy a collision needs to be effective.
- The Boltzmann distribution 玻尔兹曼分布 shows how molecular energies are spread out.
- Raising the temperature gives a big rise in rate.
The activation energy is:
Only collisions with at least the activation energy can react.
Increasing temperature increases the proportion of molecules with energy above the activation energy.
So more collisions are successful.
The Boltzmann distribution
- The curve starts at the origin, peaks, then falls in a long tail. The area under it is the total number of molecules.
- Only molecules to the right of $E_A$ have enough energy to react.
Activation energy & temperature
fraction with E ≥ Ea rises with T
Heating shifts the energy spread right — far more molecules now exceed Ea, so the rate soars.
On the Boltzmann distribution, the molecules that can react are those:
Molecules with energy greater than Eₐ (right of the line) have enough energy to react.
Match each idea to its meaning.
Each item links the term to its correct meaning.
Why temperature matters
- Raising the temperature spreads the curve to the right, so a much larger fraction of molecules now exceed $E_A$.
- Molecules also collide more often — but the first effect is the bigger one.
- That's why a small rise in temperature gives a large rise in rate.
A collision only reacts with the right orientation and enough energy
The main reason a higher temperature speeds up a reaction is that:
The curve spreads right, so far more molecules exceed Eₐ; this matters more than the increased collision rate.
A small rise in temperature can give a large rise in reaction rate.
Because the reacting fraction grows sharply with temperature, even a small increase greatly speeds the reaction.
The Boltzmann picture
- Raising temperature shifts the Boltzmann distribution, so far more molecules exceed the activation energy.
- This is why a small temperature rise can roughly double the rate.
You've got it
- activation energy $E_A$ = the minimum energy for an effective collision
- on the Boltzmann distribution, only molecules with energy > $E_A$ react
- higher temperature → curve spreads right → far more molecules exceed $E_A$ (the main effect)
- so a small temperature rise → a large rate rise