Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about exothermic and endothermic reactions, energy changes and reaction profiles (GCSE and Key Stage 3)
Enthalpy changes are an incredibly exciting area of practical chemistry that students really enjoy. It can be a challenging topic to teach as students often struggle to understand why exothermic reactions that record an increase in temperature, have a negative enthalpy change. This can be easily addressed if students understand energy profile diagrams.
There are some fantastic teacher demonstrations that can be done, such as reacting ammonium chloride with barium hydroxide.
Introducing exothermic and endothermic reactions
Key Stage 3 worksheet on exothermic and endothermic reactions. Students consider what the en- and ex- prefixes mean. Students then answer some key diagnostic questions to see whether they understand temperature and energy changes during exothermic and endothermic reactions. (PDF)
Endothermic and exothermic reactions
GCSE worksheet that asks students to use key terms to describe why a reaction is exothermic. The worksheet considers bond breaking and bond making. Students relate these processes to exothermic and endothermic reactions. (PDF)
Energy level diagrams (reaction profiles)
GCSE worksheet on energy level (enthalpy) profiles for endothermic and exothermic reactions. Students use their prior knowledge to explain why a fire keeps you warm. The worksheet also shows students how to build energy level diagrams for exothermic and endothermic reactions. Students create their own energy level diagrams for a variety of reactions. (PDF)
Using q=mcΔT and specific heat capacity
GCSE practical investigation to calculate an enthalpy change for an ice pack. Students imagine they work for a sports company that makes ice packs to treat injuries. They evaluate a reaction and determine its suitability for use in an ice pack. This method requires students to read a thermometer to the dearest 0.5 °C.
Investigation to determine how much energy is in food. Students determine which snack has more energy: Quavers or rice cakes. They calculate temperature changes per gram of food to decide whether they would take rice cakes or Quavers on their mountain adventure.
Enthalpy and dissolving
A Level thinking task on why ionic substances dissolve: entropy and enthalpy. Students think deeply to consider why ionic substances dissolve in water, even if the enthalpy change is endothermic. (PDF)