冷敷包的化学原理

研究硝酸铵的吸热溶解

Thermochemistry Beginner (Middle School) 20 分钟 ~$6.00

目标

测量硝酸铵溶于水时的温度变化，演示用于即用型冷敷包的吸热溶解过程。

背景

Ammonium nitrate dissolves endothermically in water, absorbing heat from the surroundings and causing a significant temperature drop. This principle is used in commercial instant cold packs for first aid. The dissolution has ΔH = +25.7 kJ/mol.

安全警告

  • Ammonium nitrate is an oxidizer — keep away from organic materials and heat
  • Do not mix with anything other than water for this experiment
  • Wear goggles

所需PPE

goggles

材料

  • Ammonium nitrate (NH₄NO₃) (30 g)
    Or from a commercial cold pack
  • Distilled water (100 mL)
    Room temperature

设备

Polystyrene cup calorimeter Thermometer Stirring rod Analytical balance

步骤

1

Add 100 mL of distilled water to the polystyrene cup calorimeter. Record the initial temperature.

3 分钟
2

Weigh 30 g of ammonium nitrate.

2 分钟 Ammonium nitrate is an oxidizer
3

Add the ammonium nitrate to the water. Stir gently to dissolve.

3 分钟
4

Record the temperature every 30 seconds as it drops. Note the minimum temperature.

5 分钟
5

Feel the outside of the cup — it should feel cold.

1 分钟
6

Calculate ΔH of dissolution per mole: q = mcΔT, n = mass/M(NH₄NO₃), ΔH = q/n.

5 分钟

预期结果

Temperature should drop 15-20°C. 30 g NH₄NO₃ = 0.375 mol. q = 100 × 4.18 × ΔT. Calculated ΔH should be approximately +25 kJ/mol (±15%).

清理

The ammonium nitrate solution is safe to dispose down the drain (dilute). Rinse the calorimeter.

详情

类别
Thermochemistry
难度
Beginner (Middle School)
时长
20 分钟
预估费用
$6.00
步骤数
6
材料
2

更多实验

冰的熔化焓 25 min 吸热反应演示 20 min 咖啡杯量热法 40 min 弹式量热计模拟 45 min 溶解并非总是放热的 25 min 赫斯定律验证 60 min 醋酸钠的放热结晶 30 min 金属的比热容 40 min 镁的燃烧热 50 min

Frequently Asked Questions

What is the objective of 冷敷包的化学原理?
测量硝酸铵溶于水时的温度变化，演示用于即用型冷敷包的吸热溶解过程。
How difficult is 冷敷包的化学原理?
This experiment is rated as Beginner (Middle School). It takes approximately 20 minutes to complete.
What safety precautions are needed for 冷敷包的化学原理?
Key safety precautions include: Ammonium nitrate is an oxidizer — keep away from organic materials and heat; Do not mix with anything other than water for this experiment; Wear goggles.
What materials are needed for 冷敷包的化学原理?
The main materials required are: Ammonium nitrate (NH₄NO₃), Distilled water.
What results should I expect from 冷敷包的化学原理?
Temperature should drop 15-20°C. 30 g NH₄NO₃ = 0.375 mol. q = 100 × 4.18 × ΔT. Calculated ΔH should be approximately +25 kJ/mol (±15%).