How is dry ice made in factories?

In one line

The rule

Dry ice is the solid form of carbon dioxide (CO₂), made by cooling and compressing CO₂ gas until it becomes a solid at −78.5°C.

There is no single formula, but the process uses:

• CO₂ (carbon dioxide gas)
• Pressure and cooling to turn it into a solid

Let's understand it simply

Imagine the fizz in a cold drink. That fizz is carbon dioxide gas (CO₂). Factories collect this gas from places where it is made, like in making ammonia or from burning fuels. They squeeze the gas very hard and make it super cold. When they suddenly let the pressure go, the gas turns into snow-like solid. This is dry ice.

Think of it like squeezing steam (water gas) until it becomes ice, but here it is CO₂, not water. Dry ice is much colder than normal ice and does not melt into water. It just disappears into the air (this is called "sublimation").

How it works

1. Factories collect pure CO₂ gas from chemical plants or fermentation (like making alcohol).
2. The CO₂ gas is compressed (squeezed) at high pressure, making it a liquid.
3. This liquid CO₂ is cooled to a very low temperature.
4. The pressure is suddenly released. The liquid CO₂ expands and turns into a white, snow-like solid (dry ice) by a process called "sublimation" (changing directly from gas to solid, skipping liquid).
5. The dry ice snow is pressed into blocks or pellets using machines.

The story behind it

Dry ice was first discovered in 1835 by French chemist Charles Thilorier. He noticed that when he opened a container of liquid CO₂, a white solid formed and quickly vanished. Factories started making dry ice in the early 1900s, mainly for keeping food cold during transport. The name "dry ice" was given because it does not become wet when it disappears.

Where you see it in real life

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• Ice cream carts: Dry ice keeps ice cream frozen during delivery, even in hot Indian summers.

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• Shipping vaccines: Some vaccines need to stay very cold. Dry ice helps keep them safe.

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• Stage shows: The fog you see on stage is made by putting dry ice in hot water.

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• Science labs: Dry ice is used to cool things quickly or make fun experiments.

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• Preserving food: Fish and meat are packed with dry ice to stay fresh during long journeys.

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• Removing dents: Mechanics sometimes use dry ice to pop out small dents in cars.

Why it matters

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• Dry ice is much colder than normal ice (−78.5°C vs 0°C), so it is useful for keeping things very cold.

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• It does not leave water behind, so it is perfect for shipping things that must stay dry.

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• Used in science, medicine, and food industries.

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• Questions about dry ice come in chemistry and general science exams, especially about states of matter and sublimation.

Worked example

Let’s say a factory wants to make 10 kg of dry ice.

Given: CO₂ gas collected from a chemical plant
Step 1: Compress CO₂ gas at high pressure to make it a liquid
Step 2: Cool the liquid CO₂ to a very low temperature
Step 3: Release the pressure suddenly; the liquid CO₂ turns into dry ice snow
Step 4: Collect the dry ice snow and press it into 10 kg blocks
Step 5: Store the blocks in special containers to stop them from sublimating

Common mistakes

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• Thinking dry ice is made from water: It is made from carbon dioxide, not water.

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• Believing dry ice melts into liquid: It goes straight from solid to gas (sublimation), not to liquid.

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• Touching dry ice with bare hands: It can cause burns because it is so cold.

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• Confusing dry ice with normal ice: Normal ice is frozen water; dry ice is frozen CO₂.

Remember it

Dry ice is frozen carbon dioxide that skips liquid and turns straight from solid to gas. Factories make it by squeezing and cooling CO₂ gas.