Keep It Cool! Refrigerator Quiz
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Image: iStockphoto.com/Elena Elisseeva
About This Quiz
Most people take their refrigerators for granted, except when they break down. While the main idea of how refrigerators work is fairly simple, how they are built is more complex. Chill out with this cool quiz to test your knowledge of how refrigerators work.
What is the core principle that makes refrigerators work?
Evaporating liquids absorb heat.
This principle also explains why water or alcohol feels cool on your skin, As they evaporate they absorb heat from your body.
Raising pressure lowers temperature.
Turning liquids to solids decreases temperature.
How long will it take the bacteria in your milk to spoil it if you leave it unrefrigerated?
All food has bacteria in it, but refrigerating your food slows the bacteria's work. Milk in the fridge can last a week or two.
What is special about the liquid inside your refrigerator's coils?
It evaporates at a low temperature.
Because the refrigerant evaporates so easily, it is simple to change its form between liquid and gas. This is necessary so the liquid can cool the inside of the refrigerator.
It is almost impossible to freeze it into a solid.
Why does your refrigerator need a compressor?
It compresses the refrigerant to begin the cooling cycle.
The compressor drives the system by compressing the refrigerant gas, which raises its pressure and temperature, so the heat-exchanging coils outside the fridge can cool it and turn it into a liquid, which evaporates in the coils inside the refrigerator and cools the contents.
It cools the refrigerant so it will absorb heat from inside the refrigerator.
It turns the refrigerant into a liquid.
What does your refrigerator's expansion valve do?
separates low and high pressure zones
The pressure in the outer coils is higher than in the inner coils of your refrigerator. The refrigerant has to pass through the expansion valve to get inside.
raises the refrigerant's temperature
pressurizes the refrigerant
At what temperature does water start to boil?
The boiling temperature of water at sea level is 212 degrees Fahrenheit, which equals 100 degrees Celsius. The Celsius scale is based on the freezing (zero Celsius) and boiling points of water.
What happens to water's boiling point as you go higher in the mountains?
The higher your altitude, the lower the air pressure. Lowering air pressure reduces the boiling point of any liquid.
Why does liquid nitrogen feel cold to humans even while it is boiling?
It has a very low boiling temperature.
With a boiling point of -320 degrees Fahrenheit, liquid nitrogen is much colder while boiling than the 70 degrees Fahrenheit at which most humans feel comfortable.
It causes a chemical reaction in the skin.
It makes sweat evaporate from the skin.
What is a refrigerator's regenerating cycle?
the process through which the refrigerant is repeatedly heated and cooled
By keeping its refrigerant in a closed system, a refrigerator is able to raise and lower its temperature repeatedly. This way it can keep removing heat from the inside.
the process in which the temperature inside the refrigerator is reduced
the process of the compressor turning on every 15 minutes or so
After the refrigerant leaves your refrigerator's compressor, where does it go next?
Compressing the refrigerant raises its temperature. By moving through the outer coils, the refrigerant can give off its extra heat to the air outside, and not heat up the stuff inside your refrigerator.
What creates the low-pressure area in a refrigerator's inner coils?
the compressor sucking gas out of them
By sucking the refrigerant gas out of the inner coils, the compressor reduces the pressure inside them. This is why the refrigerant later flows back in from the higher pressure outside, through the expansion valve.
a lower temperature inside than outside the refrigerator
At what temperature does ammonia boil?
Ammonia's low boiling point made it useful as a refrigerant, until other problems led to the development of a replacement.
Why don't refrigerators use pure ammonia as a refrigerant?
Inhaling pure ammonia gas is dangerous for humans. Were a refrigerator with pure ammonia refrigerant to develop a leak, it would be bad for anyone breathing in the fumes.
When were CFCs developed?
They were developed in the 1930s.
Du Pont chemicals developed chlorofluorocarbons as a safe refrigerant, replacing pure ammonia.
They were developed in the 1960s.
They always existed and were discovered, not developed.
Why did people stop using CFCs as refrigerants in new refrigerators?
They are bad for the ozone layer.
Though the discovery that CFCs harm the ozone layer was made in the 1970s, it wasn't until the 1990s that manufacturers stopped putting them into new refrigerators.
They were discovered to actually be toxic, after all.
There was a shortage of one of the chemicals that is used to make them.
What substances are used in the closed refrigeration system of a gas refrigerator?
ammonia, hydrogen and water
Although it works on the same principles as does a standard electric refrigerator, a gas refrigerator uses a more complex system to cool the inside.
ammonia, oxygen and nitrogen
hydrogen, oxygen and carbon dioxide
What does the separator in a gas refrigerator do?
separates ammonia from water
Gas refrigerators heat a solution of ammonia and water. The separator makes sure that only the ammonia moves on to the condenser.
separates water into hydrogen and oxygen
separates liquid ammonia from gaseous ammonia
What is the Peltier effect?
an electronic cooling process
The flow of electricity between copper and iron or bismuth creates a change in temperature at the junction between these metals.
the process of cooling via evaporation
a description of how something feels warm or cold in relation to something else
How do instant cold packs work?
by mixing water with ammonium-nitrate fertilizer
The mixture of water and the fertilizer creates a solution that absorbs heat. Thus, putting one on your skin will cool the contact area.
by mixing alcohol with hydrogen peroxide
by mixing liquid nitrogen with ammonia
How long do instant cold packs stay cold, and at what temperature?
10 to 15 minutes at 35 degrees Fahrenheit
Instant cold packs remain just above the freezing temperature for water, and the reaction that makes them absorb heat lasts for 10 to 15 minutes.
25 to 30 minutes at 30 degrees Fahrenheit
up to 45 minutes at 40 degrees Fahrenheit
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