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Tackling our own ice age

Choice of deicer depends on cost and effectiveness

In Canada, we are faced with melting ice along roads and paths at low temperatures.

The most commonly used deicer is ordinary salt (sodium chloride), although any water-soluble material (a solute) will have some effect.

This is because the water solution of the solute freezes at a lower temperature than does pure water.

An ice/salt mixture acts as a freezing mixture because the salt melts the ice, but, in doing so, the temperature of the mixture is lowered.

As the ice begins to melt, the salt will be diluted more and more, so that it is less effective.

The most efficient use is to allow the deicer to penetrate through the ice to loosen the ice to concrete bonds, and then scrape the whole lot off.

The choice of deicer depends on the cost and its effectiveness.

For instance, sodium chloride is relatively cheap, but only effective down to -21 C.

Fortunately, -21 C temperatures occur only a few days per year in Kamloops.

If the temperature is lower than -21 C, the salt will not work at all.

Calcium chloride is much more effective and can be used down to -50 C, but it is more expensive.

Magnesium chloride is another possible low-temperature alternative.

Unfortunately, all these materials can lead to spalling or structural damage of improperly formulated concrete, corrosion of metals and killing of vegetation along roadsides.

Urea has been suggested as a substitute.

It is non-corrosive and a good plant fertilizer, but it is much more expensive and only effective to -11 C.

We also routinely add antifreeze to car radiators to lower the freezing temperature.

Ethylene glycol is commonly used, and a 50:50 mixture with water will stop the radiator from freezing to below -40 C.

Ethylene glycol tastes sweet, but it is poisonous, so keep it stored carefully and check below the car for coolant leaks so that cats, dogs or kids don’t sample it.

Propylene glycol is much less toxic, but more expensive.

Ordinary sugar would also act as a deicer, but it is too expensive.

If you partially freeze a sugar solution, the solid that crystallizes out is almost pure water (as ice).

The liquid that is left has a higher concentration of the sugar.

This is the principle behind ice wine.

Okanagan ice-wine makers rely on -8 C temperatures to freeze out some of the water and concentrate the sugars and flavours.

For more information on this and previous articles, visit our website at biglittlesciencecentre.org.

TRY THIS AT HOME!

Make Your Own Compass

You need:

1 bar magnet, or a horseshoe magnet

A small compass

1 sewing needle

1 plastic bucket

1 Styrofoam coffee cup

Do this:

1) Set a compass down on a table. Make sure there are no magnetic objects around it (other than planet Earth). Locate magnetic north by watching which way the north end of the compass points.

2) You can make your own compass needle. Stroke a sewing needle with a bar magnet several times.

3) Make a raft out of the bottom of a Styrofoam coffee cup and poke the needle through the walls of the “raft”.

4) Set the raft down on the water in a plastic bucket, and watch it float around until the magnetized needle lines up with earth’s magnetic field.

Think about it!

Compare your homemade compass with the commercial one. Do they both point in the same direction?

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