Science doubt? plz answer this Q (esp Mr. sci teacher) (its an addition to the previous one)?
Science doubt?
Science doubt?
my sci fair proj. is
THE EFFECT OF DIFFERENT SOLUTES ON THE TEMPERATURE OF BOILING WATER.
the solutes i have used are :
sugar
salt
rock salt
baking soda
vinegar
eno
citric acid
and
disprin (the tablet)
the variation in the boiling pt is about 94 degrees C - 107 degrees celsius.
there is no drastic change
is that fine
is this project good
are my results valid ?
I AM CONFUSED!
+ i dont have the time to do it all over again or recheck my findings...
i was quite confident untill my frnd told me that THERE ISNT MUCH CHANGE AND THERE SHOULD BE A RISE NOT A FALL.....
I"M CONFUSED
Additional Details
3 minutes ago
i have added 30 g of solute to 500 ml. of water
1 minute ago
also tell me how much time does distilled water take to reach boiling pt.
Answer:
When you add a solute into water that is ionic in nature the boiling point should RISE!
An equation has been developed for this behavior and is:
∆T = i Kb m
when ∆T is the raise in temperature observed, i is a parameter base on the number of ions released into the system, Kb is a constant for the substance (determined experimentally), and m is the molarity of the substance added.
The only exception is if you add a solute that forms an azeotrope with the solvent in question (water in your case) and this COULD lead to a lower boiling fraction.
So your values of 94 to 100 do not make sense. The values above 100 - 107 do make sense.
There shouldn't be a drastic change unless your solutes are either in large enough quantities or chilled to cold temperatures before being added. So long as the boiling water has a heat source its temperature will remain relatively constant when you add small amounts of room temperature solutes. If you were to add 8 Oz of ice cold water then you should see a more drastic change.
Oh oh. You do have odd results and if you can't explain them it won't make a very impressive science fair project. You should see the temp of boiling water with solute is higher.(DONT try to change/ fake your results!!) I wonder what your procedure was like. Did you take the temp right after adding the solute or did you let it get back to boiling? If you are not in very advanced science and can explain what the problem might be you will probably do ok.
Didn't your teacher tell you to work in advance so that you could fiz problems.
your last question depends on too many variables. amount of water, heat source, temp of water to start with. you could measure using your own set up.
THere is not an answer to your question of how long does 500 ml of distilled water take to boil. The reason is I do not know your heat source and how much heat it adds per minute. The formula to find heat is H=mass(500) x specific heat(which is 1 for water X change in temperature. So you also need to know at what temperature the water started, then when the water gets to 100 degreesC, it takes the heat of vaporization to change it to steam which is 540 calories per gram.(in water, a gram is = to ml)
Starting with 30 grams of each solute, probably there is not enogh effect of other factors that I mentioned before. There should not have been a decrease in the boiling point.
Just for reference, in making candy, you can get 3 or more cups of sugar to dissolve in a cup of water and it raises the boiling point from 212 F to 220 F. Celcius degrees are larger than F so would show less change, and you added far less.
Hi Aishu,
I remember answering your first question about what solutes to use... looks like you chose good ones! Many of the above answers you are getting are going into too much detail than what you should worry about for an 8th grade science project. As a professional chemist, I can tell you that they are right that the boiling point of water with solute dissolved in it should always go up (above 100 degrees). This is called "boiling point elevation".
If you are measuring boiling points that are below 100 degrees, I suspect it is because you are measuring the temperature as soon as you see signs of boiling. Unfortunately, the point at which you see the first signs of this may not actually be the boiling point. When a liquid is heated, it will continue getting hotter until the boiling point is reached, and once this boiling point is reached it will convert into a gas until there is no liquid left. This entire process will happen at the SAME TEMPERATURE. So the best way to measure it is actually to continue waiting until the solution is vigorously boiling, and the temperature is no longer rising. Whatever this maximum temperature is will be your boiling point.
However, it may be too late for you to go back and measure things this way. Also, boiling point elevation will normally only be a few degrees for moderate amounts of solutes, so don't worry about that aspect. I would suggest that you simply stick with the results you have and do your best to explain them based on what you know. You are the scientist, and if you measured a drop in boiling point for some of your solutes, than you can report that. As long as you do your best to give an explanation as to why different solutes had different effects, you will do just fine! Hope you have fun at your science fair.
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Science doubt?
my sci fair proj. is
THE EFFECT OF DIFFERENT SOLUTES ON THE TEMPERATURE OF BOILING WATER.
the solutes i have used are :
sugar
salt
rock salt
baking soda
vinegar
eno
citric acid
and
disprin (the tablet)
the variation in the boiling pt is about 94 degrees C - 107 degrees celsius.
there is no drastic change
is that fine
is this project good
are my results valid ?
I AM CONFUSED!
+ i dont have the time to do it all over again or recheck my findings...
i was quite confident untill my frnd told me that THERE ISNT MUCH CHANGE AND THERE SHOULD BE A RISE NOT A FALL.....
I"M CONFUSED
Additional Details
3 minutes ago
i have added 30 g of solute to 500 ml. of water
1 minute ago
also tell me how much time does distilled water take to reach boiling pt.
Answer:
When you add a solute into water that is ionic in nature the boiling point should RISE!
An equation has been developed for this behavior and is:
∆T = i Kb m
when ∆T is the raise in temperature observed, i is a parameter base on the number of ions released into the system, Kb is a constant for the substance (determined experimentally), and m is the molarity of the substance added.
The only exception is if you add a solute that forms an azeotrope with the solvent in question (water in your case) and this COULD lead to a lower boiling fraction.
So your values of 94 to 100 do not make sense. The values above 100 - 107 do make sense.
There shouldn't be a drastic change unless your solutes are either in large enough quantities or chilled to cold temperatures before being added. So long as the boiling water has a heat source its temperature will remain relatively constant when you add small amounts of room temperature solutes. If you were to add 8 Oz of ice cold water then you should see a more drastic change.
Oh oh. You do have odd results and if you can't explain them it won't make a very impressive science fair project. You should see the temp of boiling water with solute is higher.(DONT try to change/ fake your results!!) I wonder what your procedure was like. Did you take the temp right after adding the solute or did you let it get back to boiling? If you are not in very advanced science and can explain what the problem might be you will probably do ok.
Didn't your teacher tell you to work in advance so that you could fiz problems.
your last question depends on too many variables. amount of water, heat source, temp of water to start with. you could measure using your own set up.
THere is not an answer to your question of how long does 500 ml of distilled water take to boil. The reason is I do not know your heat source and how much heat it adds per minute. The formula to find heat is H=mass(500) x specific heat(which is 1 for water X change in temperature. So you also need to know at what temperature the water started, then when the water gets to 100 degreesC, it takes the heat of vaporization to change it to steam which is 540 calories per gram.(in water, a gram is = to ml)
Starting with 30 grams of each solute, probably there is not enogh effect of other factors that I mentioned before. There should not have been a decrease in the boiling point.
Just for reference, in making candy, you can get 3 or more cups of sugar to dissolve in a cup of water and it raises the boiling point from 212 F to 220 F. Celcius degrees are larger than F so would show less change, and you added far less.
Hi Aishu,
I remember answering your first question about what solutes to use... looks like you chose good ones! Many of the above answers you are getting are going into too much detail than what you should worry about for an 8th grade science project. As a professional chemist, I can tell you that they are right that the boiling point of water with solute dissolved in it should always go up (above 100 degrees). This is called "boiling point elevation".
If you are measuring boiling points that are below 100 degrees, I suspect it is because you are measuring the temperature as soon as you see signs of boiling. Unfortunately, the point at which you see the first signs of this may not actually be the boiling point. When a liquid is heated, it will continue getting hotter until the boiling point is reached, and once this boiling point is reached it will convert into a gas until there is no liquid left. This entire process will happen at the SAME TEMPERATURE. So the best way to measure it is actually to continue waiting until the solution is vigorously boiling, and the temperature is no longer rising. Whatever this maximum temperature is will be your boiling point.
However, it may be too late for you to go back and measure things this way. Also, boiling point elevation will normally only be a few degrees for moderate amounts of solutes, so don't worry about that aspect. I would suggest that you simply stick with the results you have and do your best to explain them based on what you know. You are the scientist, and if you measured a drop in boiling point for some of your solutes, than you can report that. As long as you do your best to give an explanation as to why different solutes had different effects, you will do just fine! Hope you have fun at your science fair.
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