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Feeling Salty

Short answer: Sodium is a soft alkali metal that reacts with water to form sodium hydroxide (caustic soda) and hydrogen gas, giving off heat. With larger pieces, that heat can ignite the hydrogen.

A 2015 study in Nature Chemistry, filmed with high-speed cameras, suggested the violent start isn't just burning hydrogen: the metal loses electrons to the water so fast that the remaining positively charged metal ions repel each other and the surface bursts apart, a Coulomb explosion, exposing fresh metal. The title nods to table salt, sodium chloride, where sodium is tame and bound to chlorine. The footage shows a lump of metal thrown into a pond, then white bursts and spray on the water.

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What should you know about Feeling Salty?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. Sodium and water make sodium hydroxide and hydrogen.

    DD-285-F01 · Write-up · Exhibit B (The products)

  2. The initial burst may be a Coulomb explosion.

    DD-285-F02 · Write-up · Exhibit D (Coulomb explosion)

Video transcript: Feeling Salty: Drop Sodium in a Lake and the Lake Fights Back

DID YOU KNOW? Sodium is a highly reactive alkali metal that reacts violently with water. When sodium comes into contact with water it rapidly releases hydrogen gas and heat which can ignite the hydrogen causing a fiery explosion! NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 12.0s Reel ·

Video coming soonFeeling Salty · Instagram Reel
Feeling Salty: Drop Sodium in a Lake and the Lake Fights Back Instagram Reel · · 12.0s

The write-up

Drop sodium in a lake and the lake fights back. High-speed cameras suggest the first burst is a Coulomb explosion.

  1. Exhibit A

    Alkali metal

    Sodium is a soft, highly reactive alkali metal.

  2. Exhibit B

    The products

    With water it forms sodium hydroxide and flammable hydrogen gas.

  3. Exhibit C

    Heat and ignition

    The reaction releases heat that can ignite the hydrogen.

  4. Exhibit D

    Coulomb explosion

    High-speed video suggests the first burst is a Coulomb explosion of charged metal.

  5. Exhibit E

    Not table salt

    In table salt, sodium is bound to chlorine and doesn't react this way.

Questions people ask about Feeling Salty

What kind of element is sodium?

It sits in group 1 with lithium and potassium.

Source: Write-up · Exhibit A (Alkali metal) · Wikipedia: Sodium

What gas does sodium release in water?

Sodium hydroxide forms too.

Source: Write-up · Exhibit B (The products) · Wikipedia: Sodium

What can ignite the hydrogen?

Bigger pieces get hotter.

Source: Write-up · Exhibit C (Heat and ignition) · Wikipedia: Sodium

What did high-speed cameras suggest starts the burst?

Charged metal ions repel and burst apart.

Source: Write-up · Exhibit D (Coulomb explosion) · Mason et al., Nature Chemistry (2015): Coulomb explosion during the early stages of the reaction of alkali metals with water; Scientific American: Sodium's Explosive Secrets Revealed (Jan 27, 2015)

Why doesn't table salt explode in water?

Sodium chloride is stable.

Source: Write-up · Exhibit E (Not table salt) · Wikipedia: Sodium

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. What kind of element is sodium?

    1. An alkali metal
    2. A noble gas
    3. A halogen
    4. A metalloid
    Show the answer

    Answer: A. An alkali metal It sits in group 1 with lithium and potassium. Source: Write-up · Exhibit A (Alkali metal) · Wikipedia: Sodium

  2. What gas does sodium release in water?

    1. Hydrogen
    2. Oxygen
    3. Chlorine
    4. Helium
    Show the answer

    Answer: A. Hydrogen Sodium hydroxide forms too. Source: Write-up · Exhibit B (The products) · Wikipedia: Sodium

  3. What can ignite the hydrogen?

    1. The reaction's heat
    2. Sunlight
    3. Static from the water
    4. Nothing
    Show the answer

    Answer: A. The reaction's heat Bigger pieces get hotter. Source: Write-up · Exhibit C (Heat and ignition) · Wikipedia: Sodium

  4. What did high-speed cameras suggest starts the burst?

    1. A Coulomb explosion
    2. A nuclear reaction
    3. Freezing
    4. Magnetism
    Show the answer

    Answer: A. A Coulomb explosion Charged metal ions repel and burst apart. Source: Write-up · Exhibit D (Coulomb explosion) · Mason et al., Nature Chemistry (2015): Coulomb explosion during the early stages of the reaction of alkali metals with water; Scientific American: Sodium's Explosive Secrets Revealed (Jan 27, 2015)

  5. Why doesn't table salt explode in water?

    1. Its sodium is bound to chlorine
    2. It's too small
    3. It's coated
    4. It has no sodium
    Show the answer

    Answer: A. Its sodium is bound to chlorine Sodium chloride is stable. Source: Write-up · Exhibit E (Not table salt) · Wikipedia: Sodium

Cite this case file

Easterling, Marcus. "Feeling Salty." The Detail Department (DetailEnjoyer), case file DD-285, last updated Jul 30, 2024. https://detailenjoyer.com/case/feeling-salty/

Permalink: https://detailenjoyer.com/case/feeling-salty/ · Last updated

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