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Frequently Asked Questions


Q. How do you get rid of the taste of chlorine in water?
A. Just let a container of chlorinated water stand in the sun for a while. Gases do not dissolve as well when water is warmer so the chlorine will evaporate out of the water.
Q. What chemicals undergo sublimation, that is, change from solid directly to gas and vice versa without ever becoming a liquid?
A. Carbon dioxide, iodine
Q. How do movie props people make ‘smoke’ from dry ice?
A. In old black and white movies, dry ice (frozen carbon dioxide) was used to make 'smoke'. Dry ice does not make a liquid. It evaporates directly from a solid to a gas. Nowadays, a different form of smoke machine is used because it was obvious when dry ice was used, because carbon dioxide is heavier that air and the 'smoke' always flowed downwards.
Q. Why does popcorn pop?
A. The water inside the kernel expands about 300 times when it becomes gaseous. This blows the corn kernel apart.
Q. What makes the bubbles in boiling water?
A. Steam or water vapour
Q. Why does water boil at a temperature lower than 100oC on Mt Everest?
A. Mt Everest is so high that the air is 'thin' (less air pressure). That means that dissolved gas molecules and water molecules can escape more easily into the atmosphere because there is less pressure.
Q. Which cools faster - white coffee or black coffee?
A. Black coffee cools faster.
Q. Why does steam rise?
A. Hot, moist air is less dense than cool, dry air, so steam rises.