Here is the completed worksheet with explanations for each answer:
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Endothermic and Exothermic Reactions
1.
During a chemical reaction, what is always transferred?
Answer: Energy is always transferred.
Explanation: In any chemical reaction, energy is either absorbed or released, often in the form of heat, light, or sound.
2.
Describe what is meant by the "conservation of energy."
Answer: The conservation of energy means that energy cannot be created or destroyed; it can only be transformed from one form to another.
Explanation: In a chemical reaction, the total amount of energy before and after the reaction remains constant, though it may change forms (e.g., chemical energy to thermal energy).
3.
How is energy transferred in chemical reactions?
Answer: Energy is transferred through the breaking and forming of chemical bonds.
Explanation: Breaking bonds requires energy (endothermic), while forming bonds releases energy (exothermic). The net energy change determines whether the overall reaction is exothermic or endothermic.
4.
What name is given to reactions that transfer energy to the surroundings?
Answer: Exothermic reactions.
Explanation: These reactions release energy (usually as heat) into the environment, causing the surroundings to warm up.
5.
How do you know that an exothermic reaction has taken place?
Answer: You can feel the container get warmer or observe a temperature increase in the surroundings.
Explanation: Since exothermic reactions release heat, the system loses energy, and the surroundings gain it, leading to a rise in temperature.
6.
What is the name given to chemical reactions that transfer energy from the surroundings to the reactants?
Answer: Endothermic reactions.
Explanation: These reactions absorb energy from the surroundings, usually in the form of heat, causing the surroundings to cool down.
7.
Name 2 examples of an exothermic reaction.
Answer:
- Combustion of wood
- Respiration in living organisms
Explanation: Both processes release energy (as heat and/or light) into the surroundings.
8.
Name 2 examples of an endothermic reaction.
Answer:
- Photosynthesis
- Melting ice
Explanation: Photosynthesis absorbs sunlight to convert carbon dioxide and water into glucose and oxygen. Melting ice absorbs heat from the environment.
9.
What is meant by the term "thermal decomposition"?
Answer: Thermal decomposition is a chemical reaction where a compound breaks down into simpler substances when heated.
Explanation: It is an endothermic process because energy is required to break the bonds in the original compound.
10.
If a reaction gives out energy to the surroundings, what happens to the energy of the products?
Answer: The products have less chemical energy than the reactants.
Explanation: In exothermic reactions, the excess energy is released as heat, so the products are more stable and contain less stored chemical energy.
11.
Not every collision between particles results in a chemical reaction. Why?
Answer: Because not all collisions have enough energy (activation energy) or the correct orientation to break existing bonds and form new ones.
Explanation: For a reaction to occur, particles must collide with sufficient energy and proper alignment. This is known as the collision theory.
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✔ This worksheet helps students understand key concepts about energy changes in chemical reactions, including exothermic vs. endothermic processes, conservation of energy, and factors affecting reaction rates.
Parent Tip: Review the logic above to help your child master the concept of exothermic vs endothermic worksheet answers.
