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Answers to Readers' Questions on Chemistry:
Salts
The following 28 comments and questions have been sent in. They are listed according to date.
List of first 10 items
- Where are most salts found?
- What happens when you add salt to ice?
- Can I substitute for a Himalayan Salt Lamp?
- Why does salt lower the freezing point of water?
- Burned arm with ice cube dipped in salt
- Ice cream salt in a sock to reduce electric bill
- Why ice and salt burns skin
- Why does adding salt to water lower the freezing point?
- A burn from salt and ice
- Salt lamps
Where are most salts found?
Question
July 18, 2009
where are most salts found?
pamela - Kenya
18037
Answer
The ocean is made of salt water. There are various dry salt deposits where seas once were in many countries. Some are in underground caves.
What happens when you add salt to ice?
Question
April 10, 2007
Does adding salt to water make ice dissolve faster and why?
- USA
13525
Answer
Salty water has a lower freezing point than pure water. Thus, adding salt to ice will result in salty water that requires a lower temperature to freeze.
Can I substitute for a Himalayan Salt Lamp?
Question
October 18, 2006
I have seen advertisements for expensive "Himalayan Salt Lamps" which act as home ionizers. I would like to know whether placing a similar wattage lamp (40-50W) under a dish of rock salt (or another readily available salt) would produce the same ionizing effect in the home?
Thank You.
- USA
12200
Answer
You can get a salt lamp for about $30. You could probably heat a dish of rock salt and get the same ionizing effect. Although, Himalayan Salt Lamps do provide some air purification, they are also used for their looks of a light inside a large salt crystal. The amount of ionization is not that great. If you really want to purify inside air, a standard electric air ionizer is much more effective. They cost between $30 and $100.
Why does salt lower the freezing point of water?
Question
May 7, 2006
why did salt lower the freezing/melting point of ice(H2O(s))?
rids - USA
11036
Answer
Salt increases the density of water, and the freezing point is somewhat dependent on the density of the liquid.
Burned arm with ice cube dipped in salt
Question
February 28, 2006
Hey,
I was told to place an ice cube dipped in salt on my arm. It is a few inches above my wrist and it is begining to peel. It hurts. What the heck happened and what in the world can I do about it?
Hurt in Myrtle Beach - USA
10263
Answer
Ice dipped in salt can become cold enough to cause frostbite burns on the skin. Just like any type of burn, that can be painful. Put some soothing ointment on the burn and put a bandage to prevent infection. It should heal in several days.
Ice cream salt in a sock to reduce electric bill
Question
February 23, 2006
i was told that people used to put ice cream salt in a sock and put it on thier electric meter outside and this would cause the meter to slow down resulting in a lower bill. does this really work and if so why?
- USA
10202
Answer
The electric meter works by the current flowing into the house going through a small electromagnet that turns the meter. It is not affected by hot weather or freezing temperatures. I'm doubt that ice cream salt in a sock would do anything to the meter. Also, how would they know their bill was less than it was supposed to be?
Why ice and salt burns skin
Question
January 6, 2006
This comment regards two of the items copied below from your Reader Feedback page ("Got a burn from salt and ice cube" and "Ideas on why ice and salt burns skin"). Salt does decrease the freezing point of water so when salt is placed on ice the temperature of the mixture is reduced well below the 0 degrees C freezing point of pure water. This effect has been used to produce the low temperatures needed to make ice cream. It is also why salt is applied to roads and sidewalks to melt ice even when the temperature is below 0 degrees C. Yes, the ice does melt faster. Both the lowering of temperature of a mixture of salt water and ice and faster melting of the ice in that mixture is easily demonstrated by putting an ice cube in tap water (the control) and a same sized ice cube in the same amount of concentrated saltwater with a thermometer in each.
Although I do not know for sure, it seems the "burns" from salt and ice on skin is probably really frostbite from the extremely low temperature. It would not be due to a "caustic" effect. A concentrated solution of salt water at room temperature does not have the effect that the salt and ice does.
Steven - USA
9575
Answer
Thanks for the feedback on this question. The question has been quite a puzzler. The apparent explanation is that when salt is added to ice, it takes a fair amount of energy to actually melt the ice. Touching the salt and ice, starts an endothermic reaction fueling itself from body heat. In fact, the heat loss is so fast that it can give the sensation of a mild frostbite and even leave a noticeable red spot.
My remarks on the possible caustic action of the salt were incorrect.
Why does adding salt to water lower the freezing point?
Question
December 16, 2005
I konw that adding salt to ice lowers it's freezing point, but no one seems to say how this occurs? Do the splitting of the h2o molecules make the solution less dense, thus taking longer the freeze?
julie - USA
9400
Answer
When water is cooled, the molecules move slower. When it freezes, the water molecules are moving so slow that they got locked in place, as the solid ice. But when salt is added, it disrupts the process of the water becoming ice. The salt ions mixed with water require a lower temperature.
Actually, adding salt to water makes the solution denser. The more dense the water solution, the lower the freezing temperature.
A burn from salt and ice
Question
September 24, 2005
how long does it take to heal after you have a burn from the salt and ice?
and what would happen if that burn came in contact with pool chlorine, would it cause any serious damage to the skin?
lacy - USA
8278
Answer
Provided you cleaned out any excess salt in the wound, it would take at least several days to heal, just as it would with any burn or cut. Pool chlorine would kill any germs on the wound, but soaking burns or cuts in water causes them to heal slower. It is good to protect the burn with a bandage while swimming.
Salt lamps
Question
September 23, 2005
The word is out that 'SALT LAMPS' if heated, emit nigative ions in the air thus cleansing the air by attaching itself to the +tive ions in the air.How far is that true? How can NACl just emit the -Cl into the air, if it does where does the +Na go?
Kamran - Pakistan
8259
Answer
The way a salt lamp works is that when the salt is heated, it absorbs water vapor from the air to its surface. The Na and Cl ionize in the water. The negative ions neutralize any pollutants in the air and the positive charge is exchanged with an air molecule and emitted into the air. The Na and Cl go back into crystalization.
The advantage of salt lamps is that they look nice. Standard air ionizers are probably more effective for pollution control in the home.
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