Does Cold Water Boil Faster Than Hot Water?

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Waiting for water to boil isn’t exactly on our top 10 list of the most exciting household tasks, and if you’re looking for ways to speed up the process, we don’t blame you.

You might have heard that cold water boils faster than warm water, and if this is true, it suggests that you should always use cold water if you want to be more efficient with your boiling.

But does cold water actually reach boiling point faster than warm water? Is this a myth or a fact? We’ve discussed everything you need to know in this guide.

πŸ“Œ Key Takeaways:

  • No, cold water doesn’t boil faster than hot water.
  • Hot water boils faster than cold water because it’s closer to water’s boiling point already when the heating process begins.
  • Despite this, we recommend boiling water from cold, not warm, because cold water from your faucet is safe to drink and doesn’t have the risk of contamination from your heating system.

πŸ€” Does Cold Water Really Boil Faster Than Warm Water?

There’s a myth going around that cold water boils faster than warm water. We’re here to tell you that, as of the information we know right now, this is not true.

In fact, the opposite is true: warm water boils faster than cold water. In short, this is because the speed at which water boils is simply a measure of how long it takes to hit boiling point, and warm water, which already has a higher starting temperature, generally takes less time to get there.

The reason why some people claim that cold water boils faster than warm water is due to a phenomenon known as the Mpemba effect, which theorizes that hot water freezes faster than cold water due to the difference of dissolved gases and convection currents in hot water. A few scientists theorize that this effect could also apply to the reverse, saying that cold water could heat up faster than hot water. However, the Mpemba effect is very difficult to repeatedly prove, so at the moment, this remains a scientific myth.

Boiling cold water

♨️ Why Does Warm Water Boil Faster Than Cold Water?

So, why does hot water boil faster than cold? It’s because hot water starts at a higher temperature and is closer to its boiling point.

The boiling point for hot water is exactly the same: 212Β°F (assuming you’re at sea level). We know that when you heat water, you increase the kinetic energy of its molecules, causing them to move faster. When the water is already hot, the molecules are moving faster compared to cold water, which means they’re more likely to overcome the forces holding them together in their liquid state at a faster rate.

So, when you boil hot water, it needs less additional energy to reach its boiling point compared to cold water, so the boiling process is typically faster.

Boiling water in a kettle

🀨 So, Should You Boil Warm Water Instead Of Cold?

While it’s true that hot water boils faster than cold water and is therefore more efficient for boiling, we don’t generally recommend using hot tap water for boiling.

The reason for this is that water from a hot tap can potentially be contaminated, depending on your plumbing setup and age. In most modern homes with well-maintained plumbing systems, the risk of contamination from the hot faucet is relatively low. However, the risk is still there!

The biggest risk of contamination comes from the hot water heater, which can corrode and leach metals into your water over time. There’s also the risk of bacterial accumulation in the heater tank. Since cold water bypasses the heater, we recommend only using cold water for cooking and drinking purposes – even if it takes slightly longer to heat to boiling.

πŸ“‹ What Other Factors Affect Water’s Boiling Speed?

So, we know that water temperature is one of the factors affecting the speed at which water boils. But if your aim is to boil water faster, there are certain conditions aside from the temperature of your water that you should also consider:

  • The size of the pot – The greater the size and surface area of the pot you’re using to boil the water, the longer it’ll take to boil because the actual heating of the pot (something that has to happen before water will begin to heat) takes longer.
  • The volume of water – The greater the volume of water, the longer it’ll take to boil because there are more water molecules to heat. So, if you want to reduce boiling time, only boil what you need.
  • The amount of heat – The more heat you use to boil your water, and the more powerful the burner, the faster the water will boil. So turn the heat up if you want to boil your water as fast as possible.
  • The elevation – At higher altitudes, where atmospheric pressure is lower, water boils at a lower temperature. This can increase the time it takes to reach a boil compared to boiling water at sea level.
Bringing water to a rolling broil

πŸ“‘ Final Word

We wrote this article because we wanted to provide a clear explanation as to why the claim that cold water boils faster than hot water is, unless proven otherwise, currently considered a myth. Hopefully, this resource has helped to explain the process of boiling water, and the difference between boiling hot water versus cold water. But if you have any more questions, we haven’t finished yet – check out the FAQs section below to see if we’ve answered them.

  • Laura Shallcross
    Senior Editor

    Laura is a passionate residential water treatment journalist who holds an undergraduate degree in Print Journalism and a master’s degree in Creative Writing. Over a span of 5 years she's written on a range of topics including water softening, well water treatment, and purification processes.

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