Matter and Its Properties · SHS2 Chemistry

Lesson notes

Learning Objectives

Indicator: 2.1.1.LI.3 - Explain Hess’s law of constant heat summation and apply it to construct energy cycle diagrams as well as calculate relevant enthalpy changes.

By the end of the lesson, learners can:

State Hess’s law of constant heat summation in their own words.
Draw and label simple energy cycle diagrams showing alternative routes from reactants to products.
Calculate enthalpy changes of reactions using Hess’s law with given enthalpy changes of formation.
Calculate enthalpy changes of reactions using Hess’s law with given enthalpy changes of combustion.
Apply Hess’s law to determine enthalpy changes that cannot be measured directly by experiment.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Matter and Its Properties (1.1)
Content standard: 2.1.1.CS.1 - Demonstrate knowledge and understanding that energy changes occur in chemical reactions as a result of reorganization of atoms at different rates. 2.1.1.LO.1 Describe the different energy changes that occur as a result of reorganization of atoms. 3 Gender Equality and Social Inclusion 4 Socio-Emotional Learning 2.1.1.LO.2 Use the concept of chemical kinetics to explain that chemical reactions proceed at different rates depending on their conditions and design experiment to investigate these conditions.
Indicator: 2.1.1.LI.3 - Explain Hess's law of constant heat summation and apply it to construct energy cycle diagrams as well as calculate relevant enthalpy changes.
Suggested placement: Semester 1, Week 3 (Week 3 of the year)
Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.
Curriculum reference: NaCCA curriculum document, p. 63

Exemplars (from the NaCCA curriculum)

Activity-Based Learning: State Hess' law and apply it to construct simple energy cycle diagrams.
Inquiry-Based Learning:
- Carry out calculations involving-determination of enthalpy changes that cannot be found by direct experiment using thermochemical equations, energy cycles and given data. Examples: Enthalpy change of reaction from enthalpy change of combustion and enthalpy change of formation.
- Use Born-Haber cycle to determine ionization energy and electron affinity, lattice energy, dissociation energy, atomization energy, sublimation energy, etc.
Digital Learning: Watch videos to reinforce concept.
Teaching and Learning Materials:
- * Worksheets: for drawing and labelling enthalpy profile diagram. * Worksheets for supporting calculation of standard enthalpy changes. * Worksheets with task on applying Hess' law to calculate enthalpy of reaction. * Calculator * Hot water * Hydrochloric acid * Sodium hydroxide pellets * Thermometer * Copper sulphate * Zinc powder * Virtual lab on calorimetry * Use of gas syringe * Chemical balance * Calcium chloride
- * Probe
- Beakers (100ml and 400ml)
- Ammonium chloride * Calorimetry setup * Conical flask * Beakers * Marble chips * Hydrochloric acids * Kits for sulphur-clock experiment * Kits for investigating effect of of H O 2 2 * Graph sheets
- WEBSITE
- Videos on the topic:khanacademy.org
- catalyst on decomposition
Assessment (2.1.1.AS.3). The document marks these depth-of-knowledge levels for this indicator: Level 4 Extended critical thinking and reasoning.