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."

PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
News
ebooksAn unforgettable anthology of contemporary reportage
Life and Style
tech

Board creates magnetic field to achieve lift

News
There have been various incidents of social media users inadvertently flouting the law
news

Life and Style
Stack ‘em high?: quantity doesn’t always trump quality, as Friends of the Earth can testify
techThe proliferation of online petitions allows us to register our protests at the touch of a button. But do they change anything?
News
Bourgogne wine maker Laboure-Roi vice president Thibault Garin (L) offers the company's 2013 Beaujolais Nouveau wine to the guest in the wine spa at the Hakone Yunessun spa resort facilities in Hakone town, Kanagawa prefecture, some 100-kilometre west of Tokyo
i100
Sport
CSKA Moscow celebrate after equalising with a late penalty
footballCSKA Moscow 2 Manchester City 2: Premier League champions let two goal lead slip in Russia
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

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

iJobs Job Widget
iJobs General

**Primary Teachers Needed Urgently in Southport**

£80 - £120 per day: Randstad Education Liverpool: **Due to an increase in dema...

SEN Teaching Assistant Runcorn

£50 per day: Randstad Education Cheshire: SEN Teaching Assistant EBD , Septemb...

Nursery Assistant/Nurse all cheshire areas

£7 per hour: Randstad Education Cheshire: We are a large and successful recrui...

SEN Teaching Assistant

£50 per day: Randstad Education Cheshire: SEN Teaching Assistant We are curr...

Day In a Page

Indiana serial killer? Man arrested for murdering teenage prostitute confesses to six other murders - and police fear there could be many more

A new American serial killer?

Police fear man arrested for murder of teen prostitute could be responsible for killing spree dating back 20 years
Sweetie, the fake 10-year-old girl designed to catch online predators, claims her first scalp

Sting to trap paedophiles may not carry weight in UK courts

Computer image of ‘Sweetie’ represented entrapment, experts say
Fukushima nuclear crisis: Evacuees still stuck in cramped emergency housing three years on - and may never return home

Return to Fukushima – a land they will never call home again

Evacuees still stuck in cramped emergency housing three years on from nuclear disaster
Wildlife Photographer of the Year: Intimate image of resting lions claims top prize

Wildlife Photographer of the Year

Intimate image of resting lions claims top prize
Online petitions: Sign here to change the world

Want to change the world? Just sign here

The proliferation of online petitions allows us to register our protests at the touch of a button. But do they change anything?
Ed Sheeran hits back after being labelled too boring to headline festivals

'You need me, I don’t need you'

Ed Sheeran hits back after being labelled too boring to headline festivals
How to Get Away with Murder: Shonda Rhimes reinvents the legal drama

How to Get Away with Murder

Shonda Rhimes reinvents the legal drama
A cup of tea is every worker's right

Hard to swallow

Three hospitals in Leicester have banned their staff from drinking tea and coffee in public areas. Christopher Hirst explains why he thinks that a cuppa is every worker's right
Which animals are nearly extinct?

Which animals are nearly extinct?

Conservationists in Kenya are in mourning after the death of a white northern rhino, which has left the species with a single male. These are the other species on the brink
12 best children's shoes

Perfect for leaf-kicking: 12 best children's shoes

Find footwear perfect to keep kids' feet protected this autumn
Anderlecht vs Arsenal: Gunners' ray of light Aaron Ramsey shines again

Arsenal’s ray of light ready to shine again

Aaron Ramsey’s injury record has prompted a club investigation. For now, the midfielder is just happy to be fit to face Anderlecht in the Champions League
Comment: David Moyes' show of sensitivity thrown back in his face by former Manchester United manager Sir Alex Ferguson

Moyes’ show of sensitivity thrown back in his face... by Ferguson

Manchester United legend tramples on successor who resisted criticising his inheritance
Two super-sized ships have cruised into British waters, but how big can these behemoths get?

Super-sized ships: How big can they get?

Two of the largest vessels in the world cruised into UK waters last week
British doctors on brink of 'cure' for paralysis with spinal cord treatment

British doctors on brink of cure for paralysis

Sufferers can now be offered the possibility of cure thanks to a revolutionary implant of regenerative cells
Ranked seventh in world’s best tourist cities - not London, or Edinburgh, but Salisbury

Lonely Planet’s Best in Travel 2015

UK city beats Vienna, Paris and New York to be ranked seventh in world’s best tourist destinations - but it's not London