(2) Endothermic and Exothermic Reactions

Explain why burning wood is considered an exothermic reaction. Use evidence from the text to support your answer.

• Burning wood absorbs energy from the environment, making it an endothermic reaction.

• Burning wood releases stored energy, converting potential energy into kinetic energy, which makes it an exothermic reaction.

• Burning wood neither absorbs nor releases energy, so it is neither exothermic nor endothermic.

• Burning wood stores energy in the form of heat, which is why it is an exothermic reaction.

Compare and contrast exothermic and endothermic reactions in terms of energy changes and provide an example of each.

• Exothermic reactions absorb energy, while endothermic reactions release energy; examples include photosynthesis and burning wood, respectively.

• Exothermic reactions release energy, while endothermic reactions absorb energy; examples include burning wood and photosynthesis, respectively.

• Both exothermic and endothermic reactions release energy; examples include photosynthesis and burning wood.

• Both exothermic and endothermic reactions absorb energy; examples include burning wood and photosynthesis.

Design an experiment to determine whether a given chemical reaction is exothermic or endothermic. What steps would you include, and what evidence would you look for?

• Measure the temperature before and after the reaction; if the temperature increases, it is endothermic.

• Measure the temperature before and after the reaction; if the temperature decreases, it is exothermic.

• Measure the temperature before and after the reaction; if the temperature increases, it is exothermic, and if it decreases, it is endothermic.

• Measure the temperature before and after the reaction; if the temperature remains the same, it is exothermic.

Analyze the role of sunlight in photosynthesis and explain why it is necessary for this endothermic reaction.

• Sunlight provides the energy needed to break down glucose molecules, which is essential for photosynthesis.

• Sunlight provides the energy needed to combine carbon dioxide and water into glucose and oxygen, storing energy in the process.

• Sunlight is not necessary for photosynthesis as it is an exothermic reaction.

• Sunlight cools down the plant, making photosynthesis possible.

Evaluate the statement: "Instant cold packs are an example of an exothermic reaction." Use reasoning to support your answer.

• True, because instant cold packs release energy, making them exothermic.

• False, because instant cold packs absorb energy from their surroundings, making them endothermic.

• True, because instant cold packs neither absorb nor release energy.

• False, because instant cold packs store energy in the form of heat.

Predict what would happen to the temperature of the surroundings if an exothermic reaction occurs. Justify your prediction.

• The temperature of the surroundings would decrease because energy is absorbed.

• The temperature of the surroundings would increase because energy is released.

• The temperature of the surroundings would remain the same because no energy change occurs.

• The temperature of the surroundings would decrease because energy is released.

Discuss how the energy changes in photosynthesis can impact the food chain. Provide reasoning for your answer.

• Photosynthesis decreases energy in the food chain by storing energy in glucose.

• Photosynthesis increases energy in the food chain by storing energy in glucose, which can be used by plants and animals.

• Photosynthesis has no impact on the food chain as it neither stores nor releases energy.

• Photosynthesis decreases energy in the food chain by releasing energy from glucose.

Formulate a hypothesis about the effect of temperature on the rate of an endothermic reaction and describe how you would test it.

• Hypothesis: Increasing temperature will slow down an endothermic reaction. Test by measuring reaction rate at different temperatures.

• Hypothesis: Increasing temperature will have no effect on an endothermic reaction. Test by measuring reaction rate at different temperatures.

• Hypothesis: Increasing temperature will speed up an endothermic reaction. Test by measuring reaction rate at different temperatures.

• Hypothesis: Decreasing temperature will speed up an endothermic reaction. Test by measuring reaction rate at different temperatures.