In hotter water

Science questions and answers

Q How does the addition of salt affect the boiling point of water?

A Adding salt to water raises the temperature at which it boils, which is one reason why cooks put it in water - to boil things faster. Adding salt changes the chemical composition of the water (including things like the interactions between the molecules) and this alters the boiling point. The boiling point of any pure substance is always the same, but the slightest impurity can cause a change.

Q Why don't oil and water mix?

A The difference between oil and water is essentially one of charge and attraction. Water molecules are polar and attract things. This is not true for oil molecules, which are non-polar. Therefore, for energetic reasons, it's easier for oil and water to sit apart. A lot of energy is required to mix forcibly oil and water because of the repulsion of the molecules. This energy can be provided by shaking the oil and water.

Q Why do mints make your mouth feel cool?

A You might think the minty taste and cooling sensation many mints give are the effects of peppermint flavouring, but there's more to it than that. The taste of a mint is picked up by the four types of taste buds on the tongue (sweet, bitter, salty and sour) and by smell sensors in the nose. The peppermint flavouring is like a key that opens locks in the taste buds, which allow the message "Mmm, that's so minty" to be sent to the brain.

The cooling effect of a mint isn't anything to do with the peppermint flavouring or the senses of taste and smell. Cool sensations are sent to the brain along different nerves. A drop in temperature is the key that usually opens the locks in these nerves. Opening the locks allows the message "Mmm, that's so cool" to travel to the brain. But the chemical menthol in mints also opens this coolness lock, thus fooling the brain into thinking there has been a temperature drop.

Q What is the total global energy consumption per annum?

A According to the BP Statistical Review of Energy Consumption, the world used energy equivalent to 7.8 billion tonnes of oil in 1992. This figure is probably still fairly accurate as the amount of energy used per year has been fairly level for the past few years. This is because countries such as Russia have cut down on energy use.

n These questions and answers are provided by Science Line. You can use its Dial-A-Scientist service on 0345 600444.

Suggested Topics
Start your day with The Independent, sign up for daily news emails
ebooks
ebooksA special investigation by Andy McSmith
Arts and Entertainment
Larry David and Rosie Perez in ‘Fish in the Dark’
theatreReview: Had Fish in the Dark been penned by a civilian it would have barely got a reading, let alone £10m advance sales
News
Details of the self-cleaning coating were published last night in the journal Science
science
News
Approved Food sell products past their sell-by dates at discounted prices
i100
News
Life-changing: Simone de Beauvoir in 1947, two years before she wrote 'The Second Sex', credited as the starting point of second wave feminism
peopleHer seminal feminist polemic, The Second Sex, has been published in short-form to mark International Women's Day
News
i100
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

Recruitment Genius: General Manager

£50000 - £70000 per annum: Recruitment Genius: This provider of global logisti...

Recruitment Genius: Sales Manager - £70,000 OTE

£35000 - £70000 per annum: Recruitment Genius: A Sales Manager (Vice President...

Recruitment Genius: Digital Marketing Executive

£18000 - £20000 per annum: Recruitment Genius: A Digital Marketing Executive i...

Recruitment Genius: Finance Assistant / Credit Controller

£16000 - £18000 per annum: Recruitment Genius: They are an award-winning digit...

Day In a Page

Homeless Veterans campaign: Donations hit record-breaking £1m target after £300,000 gift from Lloyds Bank

Homeless Veterans campaign

Donations hit record-breaking £1m target after huge gift from Lloyds Bank
Flight MH370 a year on: Lost without a trace – but the search goes on

Lost without a trace

But, a year on, the search continues for Flight MH370
Germany's spymasters left red-faced after thieves break into brand new secret service HQ and steal taps

Germany's spy HQ springs a leak

Thieves break into new €1.5bn complex... to steal taps
International Women's Day 2015: Celebrating the whirlwind wit of Simone de Beauvoir

Whirlwind wit of Simone de Beauvoir

Simone de Beauvoir's seminal feminist polemic, 'The Second Sex', has been published in short-form for International Women's Day
Mark Zuckerberg’s hiring policy might suit him – but it wouldn’t work for me

Mark Zuckerberg’s hiring policy might suit him – but it wouldn’t work for me

Why would I want to employ someone I’d be happy to have as my boss, asks Simon Kelner
Confessions of a planespotter: With three Britons under arrest in the UAE, the perils have never been more apparent

Confessions of a planespotter

With three Britons under arrest in the UAE, the perils have never been more apparent. Sam Masters explains the appeal
Russia's gulag museum 'makes no mention' of Stalin's atrocities

Russia's gulag museum

Ministry of Culture-run site 'makes no mention' of Stalin's atrocities
The big fresh food con: Alarming truth behind the chocolate muffin that won't decay

The big fresh food con

Joanna Blythman reveals the alarming truth behind the chocolate muffin that won't decay
Virginia Ironside was my landlady: What is it like to live with an agony aunt on call 24/7?

Virginia Ironside was my landlady

Tim Willis reveals what it's like to live with an agony aunt on call 24/7
Paris Fashion Week 2015: The wit and wisdom of Manish Arora's exercise in high camp

Paris Fashion Week 2015

The wit and wisdom of Manish Arora's exercise in high camp
8 best workout DVDs

8 best workout DVDs

If your 'New Year new you' regime hasn’t lasted beyond February, why not try working out from home?
Paul Scholes column: I don't believe Jonny Evans was spitting at Papiss Cissé. It was a reflex. But what the Newcastle striker did next was horrible

Paul Scholes column

I don't believe Evans was spitting at Cissé. It was a reflex. But what the Newcastle striker did next was horrible
Miguel Layun interview: From the Azteca to Vicarage Road with a million followers

From the Azteca to Vicarage Road with a million followers

Miguel Layun is a star in Mexico where he was criticised for leaving to join Watford. But he says he sees the bigger picture
Frank Warren column: Amir Khan ready to meet winner of Floyd Mayweather v Manny Pacquiao

Khan ready to meet winner of Mayweather v Pacquiao

The Bolton fighter is unlikely to take on Kell Brook with two superstar opponents on the horizon, says Frank Warren
War with Isis: Iraq's government fights to win back Tikrit from militants - but then what?

Baghdad fights to win back Tikrit from Isis – but then what?

Patrick Cockburn reports from Kirkuk on a conflict which sectarianism has made intractable