# Enthalpy Changes and Calorimetry
*Chemistry 30, Unit A: Energy, Change and Systems*

## Slide 1: Enthalpy Changes and Calorimetry
![Enthalpy Changes and Calorimetry](https://goa-cc-uat-aili-app-001.azurewebsites.net/api/generate/8e0029b9-9728-482c-adfa-5ddd3e69b1ce/asset/2018)
*Chemistry 30, Unit A: Energy, Change and Systems*
*Sources: [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)*
> Notes: Introduce the unit theme of Energy, Change and Systems. Preview that students will quantify energy changes in chemical reactions using calorimetry and standard enthalpy data ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)).

## Slide 2: Why Study Energy in Chemical Reactions?
- Chemists quantify how much energy a reaction produces or absorbs ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)).
- Society relies on chemical reactions for usable energy, so understanding energy changes has practical impact ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)).
- Students will determine and interpret energy changes in chemical reactions ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23633)).
- Students will also explain and communicate those energy changes ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23650)).
- This unit builds on heat and temperature concepts from Science 10 and Grade 7 Science ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)).
*Sources: [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632), [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23633), [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23650)*
> Notes: Use the focusing questions from [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632) to open discussion: How does society use the energy of chemical changes? What determines whether energy is released or absorbed? Connect to prior learning on heat and temperature.

## Slide 3: From Heat Transfer to Enthalpy
1. **Measure heat transfer**: Apply Q = mcΔt to analyze heat absorbed or released by a substance ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)).
2. **Define enthalpy**: Enthalpy and molar enthalpy describe the heat content change for a chemical reaction ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636)).
3. **Use ΔH notation**: ΔH notation communicates and calculates energy changes in reactions ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638)).
4. **Classify the reaction**: Reactions are classified as endothermic or exothermic, including photosynthesis, respiration and combustion ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23643)).
*Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23643)*
> Notes: Walk through the logical sequence: students first calculate heat transfer numerically (Q = mcΔt), then connect that value to the concept of enthalpy, then represent it with ΔH notation, and finally classify the reaction type. Emphasize sign conventions: negative ΔH for exothermic, positive ΔH for endothermic.

## Slide 4: Two Ways to Find ΔH for a Reaction
**Standard Enthalpies of Formation**
Students predict the enthalpy change for a chemical equation using standard enthalpies of formation of reactants and products ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23639)). This method uses tabulated reference values rather than direct measurement.
**Hess' Law**
Hess' law allows the enthalpy change for a net reaction to be calculated by combining a series of known reactions ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23640)). This works because enthalpy is a state function, independent of the pathway taken.
*Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23639), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23640)*
> Notes: Give a worked example of each: (1) ΔH reaction = sum ΔHf products minus sum ΔHf reactants; (2) manipulating and adding two or three given reactions and their ΔH values to obtain a target equation. Check that students can flip a reaction (reverse sign of ΔH) and scale coefficients (scale ΔH proportionally).

## Slide 5: Calorimetry in Practice
In a calorimetry experiment, students measure the temperature change of a known mass of water or solution surrounding a reaction to calculate heat transfer, then use that data to determine the enthalpy change of the chemical reaction itself ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)). This experimental approach links the mathematical relationship Q = mcΔt directly to real reaction data ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)), and the resulting energy diagram shows reactants, products, enthalpy change and activation energy ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23653)).
> Determining ΔH experimentally
In a calorimetry experiment, students measure the temperature change of a known mass of water or solution surrounding a reaction to calculate heat transfer, then use that data to determine the enthalpy change of the chemical reaction itself ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)). This experimental approach links the mathematical relationship Q = mcΔt directly to real reaction data ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)), and the resulting energy diagram shows reactants, products, enthalpy change and activation energy ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23653)).
*Sources: [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23653)*
> Notes: Suggested lab: reaction of an acid and base in a coffee-cup calorimeter, or dissolving a salt in water. Have students calculate Q for the water, assume Q reaction equals negative Q water, then divide by moles of limiting reactant to find molar enthalpy. Discuss sources of error: heat loss to surroundings, calorimeter constant, incomplete reaction. Also review labeling energy diagrams with activation energy and ΔH ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23653)).

## Slide 6: Bringing It Together
**Summary:** This unit connects heat transfer calculations, enthalpy definitions, ΔH notation, Hess' law, standard enthalpies of formation and calorimetry into one framework for quantifying energy changes in chemical reactions ([Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)). Students also explain these changes at the particle level, referring to bonds breaking and forming and shifts between potential and kinetic energy ([Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23652)).
**Question:** If a calorimetry experiment measures a smaller temperature change than the true value due to heat loss to the surroundings, how would that affect the calculated molar enthalpy for an exothermic reaction?
*Sources: [Topic](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632), [Outcome](https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23652)*
> Notes: Use the closing question as an exit ticket or discussion starter. Expect students to understand calorimetry as a method to determine energy changes in chemical reactions. Extension: ask students to propose a calorimeter constant correction. Support: revisit the sign convention chart for exothermic versus endothermic ΔH before answering.

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*AILI presentation · language en · model claude-sonnet-5 · generated 2026-09-17 · id 8e0029b9-9728-482c-adfa-5ddd3e69b1ce*

### Sources

- node:n1: Unit A: Thermochemical Changes (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23632)
- node:n2: General Outcome 1 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23633)
- node:n3: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23634)
- node:n4: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23636)
- node:n5: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23638)
- node:n6: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23639)
- node:n7: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23640)
- node:n8: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23641)
- node:n9: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23643)
- node:n10: General Outcome 2 (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23650)
- node:n11: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23652)
- node:n12: Specific Outcomes for Knowledge (https://goa-cc-uat-aili-app-001.azurewebsites.net/explore/node/23653)