تفاعل الصوديوم مع الماء

مراقبة التفاعل العنيف للمعدن القلوي مع الماء

Classroom Demonstrations Advanced (University) 25 دقيقة ~$12,00

الهدف

إظهار تفاعلية المعادن القلوية بتفاعل الصوديوم مع الماء، مع ملاحظة انطلاق الهيدروجين وتكوين الهيدروكسيد.

الخلفية

Sodium metal reacts vigorously with water in a classic demonstration of alkali metal reactivity: 2Na + 2H₂O → 2NaOH + H₂. The sodium skates across the water surface as hydrogen gas is evolved, often melting into a ball from the heat of reaction. Adding phenolphthalein indicator to the water reveals the spreading pink color of NaOH as it forms. This reaction illustrates metallic bonding (soft metal), oxidation states, and the trend of increasing reactivity down Group 1.

تحذيرات السلامة

  • Sodium is highly reactive — NEVER handle with bare hands
  • Keep sodium away from water until ready for demonstration
  • Cut sodium on a dry tile; keep pieces small (pea-sized maximum)
  • Use safety shield between reaction and audience
  • Hydrogen gas is flammable — larger pieces may ignite the hydrogen
  • NaOH solution formed is corrosive
  • Never use pieces larger than a small pea for this demonstration

معدات الوقاية الشخصية المطلوبة

goggles gloves lab_coat face_shield

المواد

  • Sodium metal (1 small piece)
    Pea-sized, stored under mineral oil
  • Phenolphthalein indicator (5 mL)
    Added to water
  • Distilled water (500 mL)
  • Mineral oil (For storage)

المعدات

Large glass trough or crystallizing dish Safety shield Forceps Scalpel or knife (for cutting sodium) Filter paper Tile for cutting

الإجراء

1

Fill the trough with about 300 mL of water. Add a few drops of phenolphthalein indicator. Set up the safety shield.

3 دقيقة
2

Using forceps, remove a small piece of sodium from the mineral oil. Blot excess oil with filter paper on a dry tile.

2 دقيقة Keep all water away from cutting area
3

Cut a very small piece (no larger than a pea). Return the remainder to the mineral oil.

2 دقيقة Cut on dry surface only
4

Drop the sodium piece into the water from behind the safety shield. Step back immediately.

1 دقيقة STEP BACK after dropping
5

Observe: the sodium floats, melts into a ball, darts across the surface, fizzes (H₂ evolution), and the water turns pink (NaOH + phenolphthalein).

5 دقيقة Do not lean over the trough
6

After the reaction is complete, test the pH of the solution with pH paper (should be >12).

3 دقيقة Solution is now corrosive NaOH
7

Discuss: Group 1 reactivity trend (Li < Na < K < Rb < Cs), the redox nature of the reaction, and why sodium floats (density 0.97 g/mL < 1.0 g/mL).

7 دقيقة

النتائج المتوقعة

The sodium piece fizzes vigorously on the water surface, darting around as hydrogen is released. It melts into a shiny ball. The phenolphthalein turns the water bright pink in a spreading pattern. With very small pieces, no flame occurs; slightly larger pieces may produce a yellow sodium flame.

التنظيف

Neutralize the NaOH solution with dilute HCl before disposing down the drain. Ensure no unreacted sodium remains. Clean the trough thoroughly.

التفاصيل

الفئة
Classroom Demonstrations
الصعوبة
Advanced (University)
المدة
25 دقيقة
التكلفة التقديرية
$12,00
الخطوات
7
المواد
4

مزيد من التجارب

التجميد الفوري: الماء المبرد فائقاً 120 min الكأس المختفي (توافق معامل الانكسار) 15 min الكيمياء الضوئية مع اللومينول 30 min تفاعل الثيرميت 30 min تفاعل بريغز-راوشر المتذبذب 40 min تفاعل ساعة اليود 45 min حرق المغنيسيوم في الجليد الجاف 25 min سائل غير نيوتوني: أوبليك 20 min عمود كثافة قوس قزح 30 min معجون أسنان الفيل 20 min

Frequently Asked Questions

What is the objective of تفاعل الصوديوم مع الماء?
إظهار تفاعلية المعادن القلوية بتفاعل الصوديوم مع الماء، مع ملاحظة انطلاق الهيدروجين وتكوين الهيدروكسيد.
How difficult is تفاعل الصوديوم مع الماء?
This experiment is rated as Advanced (University). It takes approximately 25 minutes to complete.
What safety precautions are needed for تفاعل الصوديوم مع الماء?
Key safety precautions include: Sodium is highly reactive — NEVER handle with bare hands; Keep sodium away from water until ready for demonstration; Cut sodium on a dry tile; keep pieces small (pea-sized maximum).
What materials are needed for تفاعل الصوديوم مع الماء?
The main materials required are: Sodium metal, Phenolphthalein indicator, Distilled water, Mineral oil.
What results should I expect from تفاعل الصوديوم مع الماء?
The sodium piece fizzes vigorously on the water surface, darting around as hydrogen is released. It melts into a shiny ball. The phenolphthalein turns the water bright pink in a spreading pattern. With very small pieces, no flame occurs; slightly larger pieces may produce a yellow sodium flame.