Here is the step-by-step solution to determine if each reaction is endothermic or exothermic.
1. When two chemicals are mixed the temperature of the mixture increases.
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Reasoning: If the temperature goes up, it means heat is being released into the mixture. Reactions that release heat are called exothermic. The equation also shows "heat" as a product (on the right side), which confirms heat is coming out.
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Choice: b. exothermic reaction
2. A candle burns brightly and releases heat.
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Reasoning: Burning is a type of chemical reaction called combustion. All burning reactions release energy in the form of heat and light. Since heat is released, it is exothermic.
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Choice: b. exothermic reaction
3. When two chemicals are mixed their temperature drops or decreases.
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Reasoning: If the temperature goes down, the reaction is absorbing heat from its surroundings to make the reaction happen. This makes the surroundings feel cold. Reactions that absorb heat are called endothermic.
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Choice: a. endothermic reaction
4. Heat is needed to react two chemicals.
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Reasoning: The phrase "heat is needed" tells us that heat is an input for the reaction. In the equation, "heat" is on the left side with the reactants. When a reaction requires heat to start or continue, it is endothermic.
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Choice: a. endothermic reaction
5. Plants need light to make their food.
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Reasoning: This process is photosynthesis. Plants take in energy from sunlight (which is a form of heat/light energy) to convert carbon dioxide and water into glucose. Because the plant absorbs energy from the sun to make the reaction happen, it is endothermic.
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Choice: a. endothermic reaction
6. Your car burns gasoline as you drive from home to school.
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Reasoning: Just like the candle, burning gasoline is a combustion reaction. The engine burns fuel to create energy that moves the car. This process releases a lot of heat. Therefore, it is exothermic.
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Choice: b. exothermic reaction
7. Jerry is baking homemade bread in the oven.
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Reasoning: Baking involves putting dough into a hot oven. The dough absorbs heat from the oven to cook and rise. Since the reaction (cooking the bread) requires heat absorption from the outside source (the oven), it is considered an endothermic process.
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Choice: a. endothermic reaction
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Final Answer:
1. b. exothermic reaction
2. b. exothermic reaction
3. a. endothermic reaction
4. a. endothermic reaction
5. a. endothermic reaction
6. b. exothermic reaction
7. a. endothermic reaction
Parent Tip: Review the logic above to help your child master the concept of endothermic and exothermic reactions worksheet.
