Acidic sauce

Curious about what's in that famous 'raspberry sauce à la Mendelchef'?

Substances can have different properties. One of those properties is something called pH or acidity. With this, we can indicate how acidic or non-acidic (basic) they are. Here is how it works:

• If a substance has a low pH, like lemon juice, it is acidic.

• If the pH is around 7, like tap water, it is neutral.

• And if the pH is higher than 7, as with ammonia or soapsuds, it is alkaline.

Our vase contains coloured water. That colour comes from a special substance: an pH indicator. That indicator will change colour and thus be able to tell us something about the acidity of the liquid. Handy, isn't it? When you dissolve CO₂ in water, it becomes acidic. Carbon dioxide or CO₂ is the same stuff that makes bubbles in soft drinks! If you add the CO₂ ice (or dry ice) to coloured water, the water becomes acidic and changes the colour of the indicator.

When there is too much CO₂ in the air, such as from car and factory emissions, it can cause problems. When CO₂ gets into the sea, it makes the water more acidic. This is bad for the animals that live in it, such as coral reefs and shellfish. It makes it difficult for them to build up their calcium-based skeleton or shell. If the water becomes too acidic, they cannot live in it.

The solution? Emit less CO₂! One way to do this is by switching to green energy and taking more bicycles instead of cars.