Endothermic and Exothermic Reactions worksheet with scenarios for identifying heat changes in chemical and physical processes.

Here are the answers to your worksheet, with simple explanations for each one.

1. Your car burns gasoline as you drive from home to school
* Type: Exothermic
* Explanation: Burning fuel (combustion) releases energy in the form of heat and motion to move the car. Because it gives off heat, it is exothermic.

2. Jerry is baking homemade bread in the oven.
* Type: Endothermic
* Explanation: The dough needs to absorb heat from the oven to cook and rise. Since it takes in heat, it is endothermic.

3. The ice melts in your glass of water.
* Type: Endothermic
* Explanation: For solid ice to turn into liquid water, it must absorb heat energy from the surrounding water or air. Taking in heat makes it endothermic.

4. Sodium and chlorine combine in an explosive reaction to form table salt.
* Type: Exothermic
* Explanation: An explosion releases a massive amount of energy quickly. Any reaction that releases heat or light (like an explosion) is exothermic.

5. Barry lights his candles to get his hot air balloon to fly.
* Type: Exothermic
* Explanation: Lighting a candle creates a flame. Fire releases heat energy, which warms the air inside the balloon. Releasing heat is exothermic.

6. Water freezes on the pavement and the roads become icy.
* Type: Exothermic
* Explanation: When liquid water turns into solid ice, it loses heat energy to the cold air around it. Giving off heat is exothermic.

7. Mom puts a pot of water on the stove and the water begins to boil.
* Type: Endothermic
* Explanation: To make water boil, you have to add heat from the stove. The water absorbs this energy to change from a liquid to a gas. Absorbing heat is endothermic.

8. Water condenses on the side of your glass of cold lemonade.
* Type: Exothermic
* Explanation: Condensation happens when water vapor in the air touches the cold glass and turns into liquid drops. To change from a gas to a liquid, the water vapor must release its heat. Releasing heat is exothermic.

9. A glass of water left out overnight evaporates.
* Type: Endothermic
* Explanation: Evaporation is when liquid turns into a gas. The water molecules need to absorb energy from the room to escape into the air. Absorbing energy is endothermic.

10. A plant carries out photosynthesis.
* Type: Endothermic
* Explanation: Plants need sunlight (solar energy) to make their food. Since they are taking in energy from the sun to make the reaction happen, it is endothermic.

11. A tree grows.
* Type: Endothermic
* Explanation: Growing requires building new cells and structures, which takes energy. The tree gets this energy by absorbing sunlight and nutrients. Using absorbed energy makes it endothermic.

12. The snow melted when we finally had a warm day last week.
* Type: Endothermic
* Explanation: Just like ice melting in a glass, snow needs to absorb heat from the warm air to turn into water. Taking in heat is endothermic.

13. Corey adds hydrochloric acid slowly to water and notices that the flask feels hot.
* Type: Exothermic
* Explanation: If the container feels hot, it means the chemical reaction inside is releasing heat into the flask. Releasing heat is exothermic.

14. The trainer shakes a cold pack to put it on an injured student’s knee.
* Type: Endothermic
* Explanation: Cold packs work by mixing chemicals that absorb heat from their surroundings (your knee). Because the reaction takes in heat, making the area feel cold, it is endothermic.

15. An egg is cooked in a frying pan.
* Type: Endothermic
* Explanation: Cooking an egg requires heat from the pan. The egg absorbs this heat to change from raw to cooked. Absorbing heat is endothermic.