Phản Ứng Natri với Nước

Quan sát phản ứng mãnh liệt của kim loại kiềm với nước

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

Mục tiêu

Minh họa tính hoạt động của kim loại kiềm bằng cách cho natri phản ứng với nước, quan sát sự sinh khí hydro và tạo thành hydroxit.

Bối cảnh

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.

Cảnh báo an toàn

  • 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

PPE cần thiết

goggles gloves lab_coat face_shield

Vật liệu

  • 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)

Thiết bị

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

Quy trình

1

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

3 phút
2

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

2 phút 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 phút Cut on dry surface only
4

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

1 phút 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 phút 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 phút 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 phút

Kết quả dự kiến

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.

Dọn dẹp

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

Chi tiết

Danh mục
Classroom Demonstrations
Độ khó
Advanced (University)
Thời gian
25 phút
Chi phí ước tính
$12,00
Số bước
7
Vật liệu
4

Thí nghiệm khác

Chất Lỏng Phi Newton: Oobleck 20 min Cốc Thủy Tinh Biến Mất (Khớp Chiết Suất) 15 min Cột Cầu Vồng Mật Độ 30 min Đóng Băng Tức Thì: Nước Siêu Lạnh 120 min Kem Đánh Răng Voi 20 min Magie Cháy Trong Băng Khô 25 min Phản Ứng Dao Động Briggs-Rauscher 40 min Phản Ứng Đồng Hồ Iot 45 min Phản Ứng Thermit 30 min Phát Quang Hóa Học với Luminol 30 min

Frequently Asked Questions

What is the objective of Phản Ứng Natri với Nước?
Minh họa tính hoạt động của kim loại kiềm bằng cách cho natri phản ứng với nước, quan sát sự sinh khí hydro và tạo thành hydroxit.
How difficult is Phản Ứng Natri với Nước?
This experiment is rated as Advanced (University). It takes approximately 25 minutes to complete.
What safety precautions are needed for Phản Ứng Natri với Nước?
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 Phản Ứng Natri với Nước?
The main materials required are: Sodium metal, Phenolphthalein indicator, Distilled water, Mineral oil.
What results should I expect from Phản Ứng Natri với Nước?
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.