Scientist Dr Bec Thistlethwaite contributes a column to The Courier on the science in our daily lives. Readers are invited to send their science questions in to Dr Bec via [email protected]
Open a can of soft drink and you hear the hiss of escaping gas.
Pour it into a glass and bubbles race to the surface.
But the real fun begins when you take a sip and feel that sharp, tingly fizz on your tongue.
What’s really going on?
Fizzy drinks are carbonated, which means carbon dioxide gas is dissolved under pressure in the liquid.
When you open the can, the pressure is released and the gas escapes as bubbles.
That’s the part you see and hear.
But the sensation you feel isn’t just bubbles popping on your tongue, it’s chemistry.
Inside your mouth, some of that carbon dioxide reacts with water in your saliva to form a weak acid called carbonic acid.
Your tongue has special nerve endings that detect this acid.
They don’t register it as a taste exactly, but as a mild irritation.
Your brain interprets the signal as a prickly, tingling sensation.
That’s why soda feels ‘fizzy’ even if you’ve let it go flat and the bubbles have mostly disappeared.
Bubbles do still play a role, though.
As they rise and burst, they help spread the gas across your tongue, keeping the reaction going.
Temperature matters too.
Cold drinks hold more dissolved carbon dioxide, which is why chilled soda fizzes longer and feels more refreshing.
So that tickle in your mouth is really your body detecting a chemical reaction between gas and water.
It’s the same reaction that makes you burp if you drink too quickly.
The extra carbon dioxide has to escape somehow!
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