Collision theory: concentration and reacting-gas pressure
| English | Français |
|---|---|
| activation energy/ˌæktɪˈveɪʃn ˈenədʒi/ | énergie d'activation |
| collision frequency/kəˈlɪʒn ˈfriːkwənsi/ | fréquence de collision |
What would explain this observation?
- Putting more reacting particles into the same volume makes encounters more frequent. It does not automatically give each particle more energy.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Collision theory requires reacting particles to collide with each other and have sufficient energy. Activation energy · Énergie d'activation 活化能 is the minimum particle energy needed for reaction. Increasing reactant concentration in a solution places more reacting particles in a given volume, so collisions between reactants happen more often. Compressing reacting gases at the same temperature raises pressure and particle concentration, increasing collision frequency 碰撞频率. More frequent successful collisions generally increase rate.
- collision frequency: How often reacting particles collide under the stated conditions; activation energy: The minimum energy that particles must have for a reaction to occur.
At constant temperature, increasing solution concentration primarily changes which feature?
Keep frequency distinct from collision energy. At unchanged temperature, raising concentration alone does not mean particles move faster or each has more energy. In a simple stated model with one collision partner held fixed, doubling the other partner’s particle concentration can double encounter opportunities. It is not a universal measured rate law for every mechanism or for simultaneous changes to both reactants. Different reactions require suitable evidence for exact proportional relationships.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Keep frequency distinct from collision energy. At unchanged temperature, raising concentration alone does not mean particles move faster or each has more energy. In a simple stated model with one collision partner held fixed, doubling the other partner’s particle concentration can double encounter opportunities. It is not a universal measured rate law for every mechanism or for simultaneous changes to both reactants. Different reactions require suitable evidence for exact proportional relationships.
- Compare same-volume particle drawings using equal particle sizes and the same stated temperature. Count only the labelled reacting species, not solvent particles as if they were all reactants. For gas compression specify that temperature is controlled; actual compression can otherwise change temperature too. School experiments use approved dilute solutions and supplied gas data rather than student-built pressure vessels. Translate a rate claim into collision frequency and sufficient-energy reasoning.
Which two habits make the investigation or model in this case more defensible?
Compare same-volume particle drawings using equal particle sizes and the same stated temperature. Count only the labelled reacting species, not solvent particles as if they were all reactants. For gas compression specify that temperature is controlled; actual compression can otherwise change temperature too. School experiments use approved dilute solutions and supplied gas data rather than student-built pressure vessels. Translate a rate claim into collision frequency and sufficient-energy reasoning.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a supplied same-volume model increases reacting particles from 20 to 40 while the other partner and temperature stay fixed. Particle concentration doubles, consistent with twice as many encounter opportunities in the stipulated model. Compressing a fixed gas sample from 200 to 100 cm³ at the same temperature similarly doubles particles per unit volume. These ratios do not provide an exact collision count from a still picture.
A fixed gas sample is compressed from 180 to 60 cm³ at the same temperature. Find the factor increase in particles per unit volume. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A fixed gas sample is compressed from 180 to 60 cm³ at the same temperature. Find the factor increase in particles per unit volume.
The result is 3 . Known: a supplied same-volume model increases reacting particles from 20 to 40 while the other partner and temperature stay fixed. Particle concentration doubles, consistent with twice as many encounter opportunities in the stipulated model. Compressing a fixed gas sample from 200 to 100 cm³ at the same temperature similarly doubles particles per unit volume. These ratios do not provide an exact collision count from a still picture.
Check the conclusion and its limits
- Do not say greater concentration lowers activation energy or that any collision necessarily reacts. Pressure reasoning concerns gas reactants. Solvent volume changes, temperature drift and changed chemical species can invalidate a simple model comparison. The model explains a direction of change; an exact numerical rate ratio needs its stated assumptions or measured evidence.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Increasing reactant concentration necessarily lowers activation energy. This claim is false: Do not say greater concentration lowers activation energy or that any collision necessarily reacts. Pressure reasoning concerns gas reactants. Solvent volume changes, temperature drift and changed chemical species can invalidate a simple model comparison. The model explains a direction of change; an exact numerical rate ratio needs its stated assumptions or measured evidence.
Collision theory: concentration and reacting-gas pressure: Keep frequency distinct from collision energy. At unchanged temperature, raising concentration alone does not mean particles move faster or each has more energy. In a simple stated model with one collision partner held fixed, doubling the other partner’s particle concentration can double encounter opportunities. It is not a universal measured rate law for every mechanism or for simultaneous changes to both reactants. Different reactions require suitable evidence for exact proportional relationships.
Increasing reactant concentration necessarily lowers activation energy.
Do not say greater concentration lowers activation energy or that any collision necessarily reacts. Pressure reasoning concerns gas reactants. Solvent volume changes, temperature drift and changed chemical species can invalidate a simple model comparison. The model explains a direction of change; an exact numerical rate ratio needs its stated assumptions or measured evidence.
How often reacting particles collide under the stated conditions: write the technical term.
collision frequency means How often reacting particles collide under the stated conditions.