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Grade 7 · unit review

Review: Chemical Reactions and Properties

Use particle evidence and material boundaries to reason about reactions.

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Bring the unit skills together

Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.

Unit review questions
1. Which transformation category is supported by the supplied identity information? Supplied case: Salt dissolves without identity change.
Need a hint?
  • Look for the described feature: identity retained while form changes.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.
2. Supplied case 5: initial total mass (g)=90; measured portion (g)=68, using the explicitly named quantities. Unmeasured retained mass equals initial system mass minus measured portion. What result follows?
Need a hint?
  • Unmeasured retained mass equals initial system mass minus measured portion.
  • Do not call gas mass destroyed.
3. Which scientific label fits the specifically described step or feature? Supplied case: Carbon count is unchanged.
Need a hint?
  • Look for the described feature: same element counts before and after.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.
4. Which scientific label fits the specifically described step or feature? Supplied case: Outside warms as reaction supplies energy.
Need a hint?
  • Look for the described feature: net energy transferred to surroundings.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Create a four-panel explanation for “Chemical Reactions and Properties” using one supplied case from each lesson. Include the observation, scientific mechanism or calculation, result and a limitation. You may draw and speak your explanation; all inputs are supplied.

Work on paper or in your own document. Explain the choices you made.

  • Use one supplied case from each of the four lessons.
  • Name the relevant structure, quantity or process in every panel.
  • Show calculations with units or a causal evidence chain.
  • Distinguish source facts from fictional classroom data.
  • State a model limit or a condition that would change the result.
Compare with a model response

Panel 1: Pure water freezes and product identity remains H₂O. What is warranted? Which inference or prediction is best supported? Result: State changed while the supplied chemical identity was retained.. Reasoning: A physical phase change does not require new substances. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 2: Supplied case 1: initial total mass (g)=50; measured portion (g)=35, using the explicitly named quantities. Unmeasured retained mass equals initial system mass minus measured portion. What result follows? Result: 15 g. Reasoning: Substitute the supplied values: (50)-(35) = 15 g. Track the same closed boundary. A missing measurement is not missing matter. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 3: A model starts with 4 H atoms and 2 O atoms, then bonds them as two H₂O molecules. What is accounted for? Which inference or prediction is best supported? Result: The same atom totals remain in new connections.. Reasoning: Two water molecules contain 4 H and 2 O; reactions rearrange atoms rather than create the counted elements. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 4: In a supplied reaction model, the surroundings gain 20 J from the reaction system. What fits the stated boundary? Which inference or prediction is best supported? Result: Energy was transferred outward; total accounting includes surroundings.. Reasoning: Outward transfer lowers system energy relative to the receiving surroundings under this boundary. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.