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Answers to Readers' Questions on Chemistry:
Solutions
The following 25 comments and questions have been sent in. They are listed according to date.
List of first 10 items
- Why does sugar dissolve faster in hot water than in cold water?
- Why does not sand dissolve in water ?
- Why can't you filter out salt from salt water?
- Does vinegar mix with oil
- Separating salt from seaweed meal
- Why does sugar dissolve faster in hot water?
- Why is CO2 non-polar?
- How can you tell if a liquid is pure?
- Boiling temperature of salt and sugar water
- Chromatography
Why does sugar dissolve faster in hot water than in cold water?
Question
August 17, 2009
Hi!!! I'm searching for my experiment's answer:
Why does sugar dissolve faster in hot water than in cold water?
Katrina - Philippines
18157
Answer
Water molecules are moving about faster and have more energy when the water is hot than when it is cold. That means the molecules collide with the sugar molecules more often and with more energy. The sugar molecules get separated from their crystalline structure and thus dissolve faster.
Why does not sand dissolve in water ?
Question
March 1, 2009
Why sand does not dissolve in water ?
Bibi - Kuwait
17359
Answer
Sand is made of Silicon Dioxide, the same material that glass is made of. Neither dissolve in water. Materials that dissolve in water usually have a structure that causes them to break up or to ionize in water.
Why can't you filter out salt from salt water?
Question
March 1, 2009
Why can not we get the salt back from salt solution by filtering it ?
Bibi - Kuwait
17357
Answer
When salt dissolves in water, it breaks into Sodium and Chlorine ions. Filtering cannot catch these atoms. Only evaporating away the water will allow the ions to combine again into NaCl.
Does vinegar mix with oil
Question
February 4, 2008
Does vinegar mix with oil?
jane - Canada
15275
Answer
Not very well. A good experiment is to put some of each in a jar and shake it up. After a while they separate out.
Separating salt from seaweed meal
Question
January 25, 2008
How can we separate salt from other mineral substances and seaweed in a mixture of seaweed meal? What would be the easiest manner?
Rodney - Aruba
15214
Answer
You can soak the material in water and then use a filter to separate salt and mineral water from the seaweed meal. Boiling away the water will leave the salt and minerals in the container. You can also use an osmosis filter, but that is expensive and difficult.
Why does sugar dissolve faster in hot water?
Question
October 2, 2007
We have done experiments at school that prove that sugar dissolves more quickly in hot water than cold water, especially when it is stirred, but I still don't understand why this happens!
Hallam - UK
14462
Answer
When you heat water, its molecules are moving faster. That causes the water molecules to pull away the sugar molecules and put them into solution with the water faster than if the water is cold and its molecules are moving slowly.
But also, when the water is hot, its molecules are further apart, as can be seen when hot water expands. That means more sugar molecules can fit between the water molecules.
So hot ware not only dissolves the sugar faster, but it also allows more sugar to dissolve in it than with cold water.
Why is CO2 non-polar?
Question
August 2, 2007
why carbon di oxide is a non polar gas?
MOHIUDDIN - Bangladesh
14146
Answer
See the lesson on Polar and Non-Polar Molecules at:
http://www.school-for-champions.com/chemistry/polar_molecules.htm
How can you tell if a liquid is pure?
Question
April 9, 2007
in a laboratory,if teacher gives you a test to be in which there is an unknown
liquid, suggest a method to understand whether this liquid is apure substance or not?
fariha - Afghanistan
13510
Answer
Often, you can use the process of distillation or boiling to tell if the liquid is pure. If nothing is boiled off before the liquid boils, or if no residue is left when the liquid is all this still, then it is a pure liquid.
Boiling temperature of salt and sugar water
Question
October 27, 2005
Hi my name is Gabriel Peralta from La Ceiba, Honduras, Central America. I want to ask you something because I'm having a Science Fair in this month. My topic is Which kind of water will boil first? A)normal water B)salted water C)sugared water And i don't find any information. I want to ask you if you can help me by givinh me a page for the information. Thank you.
Gabriel Jesus Peralta - Honduras
8713
Answer
Salt water and sugar water are both solutions. Look in our Science lessons on Solutions for some information.
The boiling point is higher for salt and sugar water. For the experiment, you should try to make sure you put an equal amount of salt and sugar in for your tests.
The following links can help in with ideas about the experiment: http://www.physlink.com/Education/AskExperts/ae163.cfm
http://www.isd77.k12.mn.us/resources/cf/ExmSciProj.html
Chromatography
Question
October 14, 2005
Dear School For Champs Team,
I have a chromatography assignment and was wondering if you could find a bit of background information about chromatography for me? I can't seem to get what i am looking for! I need a bit of info about what chromatography is used for and, does it have anything to do with coffee filters or something? Even the smallest bit of info would be greatly appreciated!
Kind Regards,
Stella - Australia
8545
Answer
You can put a drop of water soluable material like ink on the end of a strip of wet coffee filter paper. The ink will slowly creep through the paper, spreading out into its components, according to their weight or how well they dissolve. Often the result is colored bands.
See: http://www.shodor.org/ssep/lessons/ink.html and
http://www.yesmag.bc.ca/projects/paper_chroma.html
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