Chemistry · 35 minutes
Suggested grades 10–11 · Unit 3: Rates and Dynamic Equilibrium · Lesson 1 of 2
Explain a Rate Change With Collisions
Interpret controlled concentration data and separate faster reaction from greater final yield.
Mr. S Teaches · Original starter lesson · HS-CHEM-05 · Grade range is planning guidance.Watch, notice, discuss
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Kinetics: Chemistry's Demolition Derby - Crash Course Chemistry #32
By CrashCourse
Connect the collision and activation-energy models to the lesson’s average-rate evidence; later rate-law detail is optional.
Open on YouTube: Kinetics: Chemistry's Demolition Derby - Crash Course Chemistry #32 (opens a new tab) ↗How to speed up chemical reactions (and get a date) - Aaron Sams
By TED-Ed
Compare the five rate factors with the proposed collision explanation. The dating analogy needs teacher review for the group.
Open on YouTube: How to speed up chemical reactions (and get a date) - Aaron Sams (opens a new tab) ↗What idea from the video helps you calculate two average rates and explain a collision-model hypothesis with a limitation? Identify one useful example and one limit of the video's model or explanation.
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Learning objective
Calculate two average rates and explain a collision-model hypothesis with a limitation.
Before you begin
- Read concentration and elapsed-time data.
Gather your materials
- Paper or notebook
- Pencil; calculator optional for numerical work; all task data supplied below
Language to know
- concentration
- Amount of a substance in a stated volume.
- reaction rate
- Change in a reaction quantity per unit time.
- effective collision
- A particle encounter with conditions suitable for reaction.
Understand the concept
Fictional rate report: Two runs use equal temperature, volume and reactant type. Run A begins at concentration 0.10 mol/L and forms 0.020 mol product in 20 s; B begins at 0.20 mol/L and forms 0.035 mol in 20 s. Higher concentration can increase collision frequency, but not every collision reacts. The data describe initial intervals; they do not establish final yield or a universal doubling of rate. No chemical experiment is performed in this lesson.
Teach it step by step
- Read the controlled conditions and identify concentration as the intended changed factor.
- Calculate product formed per second for each initial interval.
- Draw equal-volume particle models with different counts and explain collision frequency without making particles larger.
- Write an evidence-based rate explanation and identify missing repeated measurements or alternative differences.
Make the thinking visible
Worked example or model response
A averages 0.020/20 = 0.0010 mol/s; B averages 0.035/20 = 0.00175 mol/s. B’s initial average is 1.75 times A’s, not exactly twice. A collision explanation is consistent with the change but does not substitute for reliable experimental controls.
Guided practice
Together explain why “B ends with 1.75 times as much product” is not established by these first-20-second observations.
Independent practice
Write a five-sentence account with both rates, a particle sketch, the stated controls and a proposal for checking reproducibility. Predict qualitatively how a temperature change would introduce a second factor.
Quick assessment
Why does increased collision frequency alone not guarantee that every encounter produces a reaction?
Answer key & assessment criteria
Answers and teaching guidance
- Guided: The report measures an initial interval, not final yield; reactants, equilibrium and completion are not fully specified.
- Independent: Require accurate rates, same-size particles, clear concentration change, a qualified mechanism and repeats or uncertainty assessment.
- Quick check: Collisions also need suitable energy and orientation; the model does not treat every encounter as effective.
Look for: Assess the stated objective using the concrete criteria and explanations in the answer key. Invite an alternative supported solution; distinguish a model’s prediction from an established observation.
Make it work for your learner
More support
Use a rate fraction template and two equal-size boxes for the particle drawings.
Extension challenge
Design a two-factor concentration/temperature study on paper that can distinguish each effect rather than changing both in only two runs.
Verified references · Selected contributions
Standards connections
Selected NGSS high school-band contribution; full performance requires additional evidence and instruction.
Subject-content standards
These records identify the part of a subject standard practiced here. Course placement is instructional guidance; the source’s category or band remains authoritative.
Contributes to NGSS performance expectation
HS-PS1-5
NGSS · High school band
Explain reaction-rate changes through particle collisions and conditions.
Read the official performance expectation ↗The activity explains a concentration-related rate pattern using a simplified collision model. It does not conduct the investigation or fully test temperature, orientation, activation energy and alternate mechanisms.
Verified 2026-11-04. Selected contribution, not full attainment.
Supporting literacy connections
These records apply to the specified reading, writing or communication task. They do not establish subject-content alignment.
Supporting Common Core literacy connection
RST.9-10.1
Common Core · Grades 9–10
Use precise textual details in scientific analysis.
Read the official standard ↗The activity explicitly analyzes the provided technical text, table or model. It contributes selected literacy practice rather than complete grade-band reading coverage or independent subject-content alignment.
Verified 2026-11-04. Selected contribution, not full attainment.