溶解は常に発熱ではない

様々な塩の溶解による温度変化を比較する

Thermochemistry Beginner (Middle School) 25 分 ~$8.00

目的

様々な塩（NaOH、CaCl₂、NH₄NO₃、KNO₃）の溶解エンタルピーを比較し、溶解が発熱または吸熱になり得ることを示す。

背景

Students often assume dissolving always releases heat. This experiment tests four salts: NaOH and CaCl₂ dissolve exothermically (temperature rises), while NH₄NO₃ and KNO₃ dissolve endothermically (temperature drops). The results illustrate that lattice energy vs hydration energy determines the sign of ΔH.

安全上の警告

  • NaOH is extremely corrosive
  • NH₄NO₃ is an oxidizer
  • Wear goggles and gloves

必要なPPE

goggles gloves

材料

  • Sodium hydroxide pellets (10 g)
    Exothermic
  • Calcium chloride (10 g)
    Exothermic
  • Ammonium nitrate (10 g)
    Endothermic
  • Potassium nitrate (10 g)
    Endothermic
  • Distilled water (400 mL)

器具

4 polystyrene cups Thermometer Stirring rod Analytical balance

手順

1

Add 100 mL water to each of four labeled cups. Record the initial temperature of each.

5 分
2

Add 10 g NaOH to cup 1. Stir and record the maximum temperature.

3 分 Very exothermic — NaOH is corrosive
3

Add 10 g CaCl₂ to cup 2. Stir and record the maximum temperature.

3 分
4

Add 10 g NH₄NO₃ to cup 3. Stir and record the minimum temperature.

3 分
5

Add 10 g KNO₃ to cup 4. Stir and record the minimum temperature.

3 分
6

Create a table ranking the salts from most exothermic to most endothermic.

3 分
7

Discuss why some dissolve exothermically and others endothermically (lattice energy vs hydration energy).

5 分

予想される結果

NaOH: +15-20°C rise. CaCl₂: +10-15°C rise. NH₄NO₃: -15-20°C drop. KNO₃: -5-10°C drop. Clear demonstration that dissolution can be either exothermic or endothermic.

後片付け

NaOH and CaCl₂ solutions should be neutralized before disposal. All solutions can be poured down the drain after dilution.

詳細

カテゴリ
Thermochemistry
難易度
Beginner (Middle School)
所要時間
25 分
推定費用
$8.00
ステップ数
7
材料
5

その他の実験

コーヒーカップ熱量測定 40 min コールドパックの化学 20 min ヘスの法則の検証 60 min マグネシウムの燃焼熱 50 min 吸熱反応のデモンストレーション 20 min 氷の融解エンタルピー 25 min 爆弾熱量測定シミュレーション 45 min 酢酸ナトリウムの発熱結晶化 30 min 金属の比熱容量 40 min

Frequently Asked Questions

What is the objective of 溶解は常に発熱ではない?
様々な塩（NaOH、CaCl₂、NH₄NO₃、KNO₃）の溶解エンタルピーを比較し、溶解が発熱または吸熱になり得ることを示す。
How difficult is 溶解は常に発熱ではない?
This experiment is rated as Beginner (Middle School). It takes approximately 25 minutes to complete.
What safety precautions are needed for 溶解は常に発熱ではない?
Key safety precautions include: NaOH is extremely corrosive; NH₄NO₃ is an oxidizer; Wear goggles and gloves.
What materials are needed for 溶解は常に発熱ではない?
The main materials required are: Sodium hydroxide pellets, Calcium chloride, Ammonium nitrate, Potassium nitrate, Distilled water.
What results should I expect from 溶解は常に発熱ではない?
NaOH: +15-20°C rise. CaCl₂: +10-15°C rise. NH₄NO₃: -15-20°C drop. KNO₃: -5-10°C drop. Clear demonstration that dissolution can be either exothermic or endothermic.