Australian Curriculum v9 / ACiQ Year 10 Science - Unit 3 - Reaction patterns and reaction rates

Reaction patterns and reaction rates

Classify common reaction patterns and use collision theory to explain effects of temperature, concentration, surface area and catalysts.

Updated 2026-07-26 - 13 min read

Reaction patterns and reaction rates is taught here as a connected set of decisions, not a list of facts. Work through the prerequisite recall, explicit models, carefully faded examples, misconception repairs and transfer task before using the target in Check, Practice, Review or Rapid Revision.

This note is designed to work with the guided lessons, curated practice, flashcards, Tutor context, Review and Rapid Revision for the same canonical target. The same three evidence checks are used throughout, so feedback can route a learner back to the precise idea that needs repair.

Reaction patterns

Reaction classes such as combustion, decomposition, precipitation and acid reactions are identified from reactant-product relationships and evidence. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.

A dependable reasoning routine

Define the system or phenomenon and identify the change being explained.
Trace the mechanism for reaction patterns in causal order rather than listing disconnected terms.
Link each claim to an observation, measurement, model or accepted scientific relationship.
State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: Combustion requires reaction with oxygen; energy change alone is insufficient.

The repair matters because the shortcut may appear to work in one familiar example while failing when the system boundary, causal mechanism, variable or evidence limit changes. Use the routine above to make the reasoning visible enough for another learner to verify.

Example 1.1

Which statement correctly explains reaction patterns?

Step 1 - identify the governing idea: Reaction classes such as combustion, decomposition, precipitation and acid reactions are identified from reactant-product relationships and evidence.

Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.

Result: Reaction classes such as combustion, decomposition, precipitation and acid reactions are identified from reactant-product relationships and evidence.

The evidence-to-mechanism link is: It states the governing scientific relationship and its conditions. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

Any reaction that heats is combustion. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 1.2

A student says: "Any reaction that heats is combustion." What is the best correction?

Step 1 - identify the governing idea: Reaction classes such as combustion, decomposition, precipitation and acid reactions are identified from reactant-product relationships and evidence.

Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.

Result: Combustion requires reaction with oxygen; energy change alone is insufficient.

The evidence-to-mechanism link is: The correction identifies the precise conceptual error and replaces it with a testable explanation. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 1.3

Two solutions produce an insoluble solid. Pattern?

Step 1 - identify the governing idea: Reaction classes such as combustion, decomposition, precipitation and acid reactions are identified from reactant-product relationships and evidence.

Step 2 - apply it to this evidence: Dissolved ions combine into a solid product.

Result: Precipitation

The evidence-to-mechanism link is: Dissolved ions combine into a solid product. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Dissolved ions combine into a solid product.
An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Collision theory

Reaction rate increases when successful collision frequency rises; collisions require sufficient energy and suitable orientation. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.

A dependable reasoning routine

Define the system or phenomenon and identify the change being explained.
Trace the mechanism for collision theory in causal order rather than listing disconnected terms.
Link each claim to an observation, measurement, model or accepted scientific relationship.
State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: Only a fraction of collisions meet energy and orientation conditions.

Example 2.1

Which statement correctly explains collision theory?

Step 1 - identify the governing idea: Reaction rate increases when successful collision frequency rises; collisions require sufficient energy and suitable orientation.

Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.

Result: Reaction rate increases when successful collision frequency rises; collisions require sufficient energy and suitable orientation.

Why the alternatives fail:

Every particle collision forms products. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 2.2

A student says: "Every particle collision forms products." What is the best correction?

Step 1 - identify the governing idea: Reaction rate increases when successful collision frequency rises; collisions require sufficient energy and suitable orientation.

Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.

Result: Only a fraction of collisions meet energy and orientation conditions.

Why the alternatives fail:

Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 2.3

Why does higher concentration often increase rate?

Step 1 - identify the governing idea: Reaction rate increases when successful collision frequency rises; collisions require sufficient energy and suitable orientation.

Step 2 - apply it to this evidence: Collision frequency increases.

Result: More reactant particles per volume create more frequent collisions

The evidence-to-mechanism link is: Collision frequency increases. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Collision frequency increases.
An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Catalysts and rate variables

A catalyst provides an alternative pathway with lower activation energy and is regenerated overall. Use the model to make a prediction, connect it to observable evidence and state any relevant condition or limitation.

A dependable reasoning routine

Define the system or phenomenon and identify the change being explained.
Trace the mechanism for catalysts and rate variables in causal order rather than listing disconnected terms.
Link each claim to an observation, measurement, model or accepted scientific relationship.
State the boundary of the conclusion: what was tested, what remains uncertain and what evidence would strengthen it.

Repair: It changes rate, not the equilibrium-limited yield, and is not used up overall.

Example 3.1

Which statement correctly explains catalysts and rate variables?

Step 1 - identify the governing idea: A catalyst provides an alternative pathway with lower activation energy and is regenerated overall.

Step 2 - apply it to this evidence: It states the governing scientific relationship and its conditions.

Result: A catalyst provides an alternative pathway with lower activation energy and is regenerated overall.

Why the alternatives fail:

A catalyst increases product amount by being consumed. — It conflicts with the stated mechanism or evidence: It states the governing scientific relationship and its conditions.
A single observation proves the claim in every context. — It changes the system boundary or claims a cause that the supplied observations do not establish.
The scientific terms can be rearranged without changing the mechanism. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 3.2

A student says: "A catalyst increases product amount by being consumed." What is the best correction?

Step 1 - identify the governing idea: A catalyst provides an alternative pathway with lower activation energy and is regenerated overall.

Step 2 - apply it to this evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.

Result: It changes rate, not the equilibrium-limited yield, and is not used up overall.

Why the alternatives fail:

Repeat the claim with more technical vocabulary. — It conflicts with the stated mechanism or evidence: The correction identifies the precise conceptual error and replaces it with a testable explanation.
Ignore conflicting evidence. — It changes the system boundary or claims a cause that the supplied observations do not establish.
Treat the model as a literal picture with no limits. — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Example 3.3

Why does powder react faster than a lump of equal mass?

Step 1 - identify the governing idea: A catalyst provides an alternative pathway with lower activation energy and is regenerated overall.

Step 2 - apply it to this evidence: Surface area changes collision opportunity.

Result: Greater exposed surface permits more collisions per second

The evidence-to-mechanism link is: Surface area changes collision opportunity. Notice that the conclusion does not extend beyond the stated system or evidence. A scientific explanation must trace cause and effect, not only name the relevant vocabulary.

Why the alternatives fail:

A conclusion that ignores the named mechanism — It conflicts with the stated mechanism or evidence: Surface area changes collision opportunity.
An answer based on one familiar keyword — It changes the system boundary or claims a cause that the supplied observations do not establish.
A claim that exceeds the available evidence — It extends the conclusion beyond the evidence. A valid answer must preserve the variables, sequence and uncertainty in the prompt.

Retrieval check

Try these without looking back at the examples.

A student says: "Any reaction that heats is combustion." What is the best correction?
A student says: "Every particle collision forms products." What is the best correction?
A student says: "A catalyst increases product amount by being consumed." What is the best correction?

Answers

Combustion requires reaction with oxygen; energy change alone is insufficient. — The correction identifies the precise conceptual error and replaces it with a testable explanation.
Only a fraction of collisions meet energy and orientation conditions. — The correction identifies the precise conceptual error and replaces it with a testable explanation.
It changes rate, not the equilibrium-limited yield, and is not used up overall. — The correction identifies the precise conceptual error and replaces it with a testable explanation.

Transfer task

Find an unfamiliar example from school, daily life, a credible news source or another subject. Explain which of the three evidence checks applies. Complete the task, then audit your own response: identify the evidence used, the relationship applied, one plausible misconception and the final reasonableness check. If a peer could not reproduce your reasoning, add the missing step.

Reaction patterns and reaction rates

Reaction patterns

A dependable reasoning routine

Example 1.1

Example 1.2

Example 1.3

Collision theory

A dependable reasoning routine

Example 2.1

Example 2.2

Example 2.3

Catalysts and rate variables

A dependable reasoning routine

Example 3.1

Example 3.2

Example 3.3

Retrieval check

Answers

Transfer task

Sources