Pupils pour cold water on candle experiment

THE school experiment looks simple. To show how much oxygen is in air, you stand a candle in some water, cover it with a large jar and wait for the candle to burn out. When it does, the water rises up the jar, sucked up by the lack of oxygen.

Except that this longstanding experiment, used by secondary school teachers around the world for decades, is a sham - as three schoolchildren have demonstrated.

Emma, Andrew and Rebecca Fist, aged 9, 11 and 12, of Norwood in Tasmania, decided to burn the oxygen up faster, and did the same experiment with three candles. To their surprise, they found that the water rose further up the jar - even allowing for the extra volume taken up by the candles' bases. "The water level rises much more. Why?" they wrote to New Scientist magazine.

Now, the truth has emerged: the experiment does not really show the effects of the air's oxygen depletion, but how much it shrinks when the air cools after the candle, or candles, go out.

Answering the children's question, Ian Russell, of Interactive Science Ltd, in High Peak Derbyshire, who designs hands-on science experiments, commented: "Congratulations to the children, who experimentally disproved the common textbook misconception."

He said that the principal effect making the water rise is that the candle flames heat the air around them before the jar is placed over them. "There is a short pause after the candles go out, and only then does the water level rise as the remaining air cools and contracts again." As other scientists pointed out, when the candle's hydrocarbons burn, they produce carbon dioxide - a gas that dissolves a little in water - and water vapour. The volume of oxygen lost does not match the change in water level.

Yesterday, Mr Russell said that errors like these are common in school science texts. "I call them textbook viruses: they get propagated from generation to generation."

Start your day with The Independent, sign up for daily news emails
Have you tried new the Independent Digital Edition apps?
ebooks
ebooksAn introduction to the ground rules of British democracy
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
SPONSORED FEATURES
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Guru Careers: Trainer / IT Trainer

£30 to £32k : Guru Careers: We are seeking a Trainer / IT Trainer to join an a...

Recruitment Genius: Fence Installer - Commercial

£25000 - £35000 per annum: Recruitment Genius: This privately owned Fencing Co...

Recruitment Genius: Sales Executive - OTE £22,000

£17000 - £22000 per annum: Recruitment Genius: If you answer yes, this company...

Recruitment Genius: Project / Account Manager and IT Support

£18000 - £25000 per annum: Recruitment Genius: This world leader in Online Pro...

Day In a Page

Mullah Omar, creator of the Taliban, is dead... for the fourth time

Mullah Omar, creator of the Taliban, is dead... again

I was once told that intelligence services declare their enemies dead to provoke them into popping up their heads and revealing their location, says Robert Fisk
Margaret Attwood on climate change: 'Time is running out for our fragile, Goldilocks planet'

Margaret Attwood on climate change

The author looks back on what she wrote about oil in 2009, and reflects on how the conversation has changed in a mere six years
New Dr Seuss manuscript discovered: What Pet Should I Get? goes on sale this week

New Dr Seuss manuscript discovered

What Pet Should I Get? goes on sale this week
Oculus Rift and the lonely cartoon hedgehog who could become the first ever virtual reality movie star

The cartoon hedgehog leading the way into a whole new reality

Virtual reality is the 'next chapter' of entertainment. Tim Walker gives it a try
Ants have unique ability to switch between individual and collective action, says study

Secrets of ants' teamwork revealed

The insects have an almost unique ability to switch between individual and collective action
Donovan interview: The singer is releasing a greatest hits album to mark his 50th year in folk

Donovan marks his 50th year in folk

The singer tells Nick Duerden about receiving death threats, why the world is 'mentally ill', and how he can write a song about anything, from ecology to crumpets
Let's Race simulator: Ultra-realistic technology recreates thrill of the Formula One circuit

Simulator recreates thrill of F1 circuit

Rory Buckeridge gets behind the wheel and explains how it works
Twitter accused of 'Facebookisation' over plans to overhaul reverse-chronological timeline

Twitter accused of 'Facebookisation'

Facebook exasperates its users by deciding which posts they can and can’t see. So why has Twitter announced plans to do the same?
Jane Birkin asks Hermès to rename bag - but what else could the fashion house call it?

Jane Birkin asks Hermès to rename bag

The star was shocked by a Peta investigation into the exotic skins trade
10 best waterproof mascaras

Whatever the weather: 10 best waterproof mascaras

We found lash-enhancing beauties that won’t budge no matter what you throw at them
Diego Costa biography: Chelsea striker's route to the top - from those who shared his journey

Diego Costa: I go to war. You come with me...

Chelsea's rampaging striker had to fight his way from a poor city in Brazil to life at the top of the Premier League. A new book speaks to those who shared his journey
Ashes 2015: England show the mettle to strike back hard in third Test

England show the mettle to strike back hard in third Test

The biggest problem facing them in Birmingham was the recovery of the zeitgeist that drained so quickly under the weight of Australian runs at Lord's, says Kevin Garside
Women's Open 2015: Charley Hull - 'I know I'm a good golfer but I'm also just a person'

Charley Hull: 'I know I'm a good golfer but I'm also just a person'

British teen keeps her feet on ground ahead of Women's Open
Turkey's conflict with Kurdish guerrillas in Iraq can benefit Isis in Syria

Turkey's conflict with Kurdish guerrillas in Iraq can benefit Isis in Syria

Turkish President Erdogan could benefit politically from the targeting of the PKK, says Patrick Cockburn
Yvette Cooper: Our choice is years of Tory rule under Jeremy Corbyn or a return to a Labour government

Our choice is years of Tory rule under Corbyn or a return to a Labour government

Yvette Cooper urged Labour members to 'get serious' about the next general election rather than become 'a protest movement'