📚 Investigating Endothermic Changes | 探究吸热变化
In this investigation, you will explore endothermic changes - chemical or physical processes that absorb energy from their surroundings and cause a temperature decrease. By measuring temperature changes when certain substances are mixed with water, you can identify whether a reaction is endothermic and practise key scientific skills such as controlling variables, recording data and evaluating evidence.
在本次探究中，你将研究吸热变化——即从周围环境吸收能量并导致温度下降的化学或物理过程。通过测量某些物质与水混合时的温度变化，你可以判断反应是否吸热，并练习控制变量、记录数据和评估证据等关键科学技能。
1. What Are Endothermic Changes? | 什么是吸热变化？
An endothermic change is a process that takes in energy, usually as heat, from its surroundings. The word 'endothermic' comes from 'endo-' meaning inside and 'therm' meaning heat, so energy goes into the system.
吸热变化是从周围环境中吸收能量（通常为热能）的过程。'endothermic' 一词中，'endo-' 表示内部，'therm' 表示热，因此能量进入体系。
During an endothermic reaction, the temperature of the surroundings falls because heat energy is transferred from the surroundings to the reacting substances. This temperature drop is an observable sign that the change is endothermic.
在吸热反应中，周围环境温度下降，因为热能从周围环境传递给反应物。这种温度下降是判断变化为吸热的一个可观察标志。
2. Energy Transfer in Endothermic Reactions | 吸热反应中的能量转移
In any chemical reaction, bonds between atoms are broken and new bonds are formed. Breaking bonds requires energy, while forming bonds releases energy. In an endothermic reaction, more energy is needed to break bonds than is released when new bonds form, so the reaction absorbs net energy from its surroundings.
在任何化学反应中，原子之间的化学键断裂并形成新键。断键需要能量，而成键释放能量。在吸热反应中，断键所需能量大于成键释放的能量，因此反应从周围环境净吸收能量。
This net energy intake lowers the kinetic energy of nearby particles, which is measured as a fall in temperature. The reaction vessel feels cold because it is losing heat to the reaction.
这种净能量吸收降低了附近粒子的动能，宏观上表现为温度下降。反应容器摸起来很冷，因为它正在将热量传递给反应体系。
3. Everyday Examples of Endothermic Changes | 日常生活中的吸热变化实例
Everyday examples of endothermic changes include photosynthesis, where plants absorb light energy, and cold packs used for sports injuries. Instant cold packs often rely on the dissolving of ammonium nitrate or the reaction between citric acid and sodium hydrogencarbonate.
日常生活中的吸热变化实例包括植物吸收光能的光合作用，以及用于运动损伤的冷敷包。速冷冷敷包通常利用硝酸铵溶解或柠檬酸与碳酸氢钠的反应。
In the laboratory, a common endothermic demonstration is mixing citric acid solution with sodium hydrogencarbonate. The mixture fizzes and its temperature drops noticeably.
在实验室中，一个常见的吸热演示是将柠檬酸溶液与碳酸氢钠混合。混合物冒泡，温度明显下降。
Some physical changes, such as the dissolving of ammonium chloride in water, are also endothermic. Ice melting is endothermic because it absorbs heat to weaken the forces holding water molecules in a solid lattice.
一些物理变化，如氯化铵溶于水，也是吸热过程。冰融化也是吸热过程，因为它吸收热量以削弱将水分子固定在固体晶格中的作用力。
4. Aim of the Investigation | 探究目的
The aim of this investigation is to measure the temperature change when a solid is dissolved or reacted, and to use the results to decide whether the change is endothermic.
本次探究的目的是通过测量固体溶解或反应时的温度变化，并利用结果判断该变化是否吸热。
A simple, safe system for KS3 is to add a measured mass of sodium hydrogencarbonate to a measured volume of citric acid solution in an insulated cup, and record the temperature every 30 seconds.
对于 KS3，一个简单安全的体系是：在隔热杯中加入一定质量的碳酸氢钠和一定体积的柠檬酸溶液，每 30 秒记录一次温度。
A control experiment with the same volume of water and no solid can help you see that the temperature drop is caused by the reaction, not by the room or stirring.
使用同体积水且不加固体的对照实验可以帮助你
Published by TutorHao | KS3 Chemistry Revision Series | aleveler.com
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