Question 15
Which gas is sealed inside packets of milk powder?
The right answer is the one marked above.
Nitrogen. It is used as a blanketing gas — its low reactivity is exactly what makes it useful, because it keeps oxygen away from what is being stored.
The same property gives nitrogen its other uses: filling electric bulbs and thermometers, providing an inert atmosphere when making electronic devices, and filling vehicle tyres. Liquid nitrogen is used for something different again — as a very low temperature cooling agent.