Lesson 1: Introduction to Heat and Energy
Curriculum Expectations
D2.3 solve problems involving analysis of heat transfer in a chemical reaction, using the equation Q = mc∆T (e.g., calculate the energy released in the combustion of an organic com- pound, and express the results in energy per mole of fuel [J/mol])
D3.1 compare the energy changes resulting from physical change (e.g., boiling water), chemical reactions (e.g., bleaching a stain), and nuclear reactions (e.g., fission, fusion) in terms of whether energy is released or absorbed.
D3.3 explain how mass, heat capacity, and change in temperature of a substance determine the amount of heat gained or lost by the substance
D3.1 compare the energy changes resulting from physical change (e.g., boiling water), chemical reactions (e.g., bleaching a stain), and nuclear reactions (e.g., fission, fusion) in terms of whether energy is released or absorbed.
D3.3 explain how mass, heat capacity, and change in temperature of a substance determine the amount of heat gained or lost by the substance
Lesson Hook: Enthalpy of Dissolution - CuSO4
- This is an excellent teacher-led demonstration that illustrates changes in energy during reactions. During the chemical reaction between water and anhydrous CuSO4, students will observe a colour change as well as evolution of heat through temperature change.
- The demonstration lends itself to a discussion of the nature of energy and chemical reactions - the idea that some reactions release energy and others require energy.
Equipment
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Safety Precautions
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Procedure
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Suggested approach:
- Facilitate a discussion to elicit prior knowledge of students. Establish what they think the relationship between reactions and energy and have students give examples of common reactions associated with energy.
- Introduce the demonstration, asking if students have seen CuSO4 in solution before (a clear, blue solution). Demonstrate the blue colour in the clear beaker (step 3 of procedure). Ask students if this is a chemical or physical reaction.
- Following the demonstration, ask students how would they determine how much energy was released to the water using the information they know about the reactants (amount, temperature). This ties in to the rest of the lesson, involving specific heat capacities and energy calculations.
Activity modified from Grade 12 Chemistry - McGraw Hill (p.277)
Pedagogical Approach
Drawing connections:
- Elicit prior knowledge and encourage extended thinking from students by asking how you would measure the amount of energy that was released by the reaction. What is known about the experiment, what is unknown?
- The discussion can also be approached from a mathematical/logical perspective. What are the important factors of the experiment that we can use to find the energy released? Heat energy is related to temperature - what did we measure the temperature of? After small-groups discussion, elicit responses from students about what can be used to find the energy. Eventually, the mass and temperature of the water will be the most important aspects, so how do we get from those values to energy.
- From this point, examine the units with the class (i.e. Q = mass* _____* temperature change :: (J) = (g) * __ * (°C)). What are we missing from this equation in order to get to a unit of Joules? This is an alternative way of introducing specific heat capacity which allows for students to derive the units themselves.
- Connect these ideas of chemical change to physical and nuclear reactions through discussion and note with the class.
Consolidation: Exit Card
- Ask students to give an example of an open, closed and isolated system.
- Describe (in words) how to calculate the energy released from a chemical reaction using temperature change.