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WOW! in the Classroom

Reaction Chemistry - Endothermic vs. Exothermic

The idea that energy is constant but can be converted into different forms and transferred as heat is presented. Students will learn about the difference between endothermic and exothermic reactions. They will be introduced to decomposition and neutralization reactions as well as learn about catalysts. Phase transitions, specifically gas formation, and their application to pressure volume work is presented in a fun and exciting way! (Most appropriate for grade levels 7-9.)
**This lesson includes a power point presentation. This section can be handled with print-outs if needed. Due to the nature of the reactions, access to a sink for post lesson cleanup is desired.

Lesson Time: 45-60 minutes

Adult Demonstration 1: The exothermic decomposition of hydrogen peroxide is catalyzed with yeast and the heat generated is monitored using a Vernier probe.

Student Activity 1: The concept of a catalyst is acted out by students using a gym scooter.

Adult Demonstration 2: The endothermic decomposition/neutralization of sodium bicarbonate and acetic acid is demonstrated. The temperature change is monitored using a Vernier probe.

Adult Demonstration 3: The above reaction is repeated with a test tube and a balloon in order to demonstrate the ability of the gas formed to do pressure-volume work.

Student Activity 2: Sodium bicarbonate and citric acid tabs are combined with water to fuel small film canister “rockets.” This activity reinforces the idea that chemical reactions can be used to do work.

Group work: Students will need to work in groups of 2 for the final activity. In order to save time, teachers are
asked to create the groups before Wizard arrives.


Standards
:
6.PS.1
Matter is made up of small particles called atoms. Elements are a class of substances composed of a single kind of atom.  Molecules are the combination of two or more atoms that are joined together chemically.
6.PS.2 Temperature is a measure of the average motion of the particles in a substance. Energy transfer can result in a change in temperature or a phase change. When substances undergo changes of state, atoms change their motion and position. Heat is a process of energy transfer rather than a type of energy.
6.PS.3 There are two categories of energy: kinetic and potential. Objects and substances in motion have kinetic energy. Objects and substances can have energy as a result of their position (potential energy).
7.PS.2 When substances interact and form new substances the properties of the new substances may be very different from those of the original substances, but the amount of mass does not change.
7.PS.3 Energy can be transformed or transferred but never lost
7.PS.4 Energy can be transferred in a variety of ways.
8.PS.2  Forces can act to change the motion of objects
PS.EW.1 Conservation of energy: Quantifying kinetic energy; quantifying gravitational potential energy
PS.EW.2 Transfer and transformation of energy (including work)
PS.M.5 Reactions of matter: Chemical reactions