INFORMATION NEEDED IN THIS RESPONSE

• States that concentration is the amount of material dissolved in equal volumes of liquid.
• States that the solution with the most solute in a given volume of liquid is most concentrated.
• States that the volumes of the solvent must be equal to compare the amounts of solute in each to determine comparative concentration
• Explanation of the quantities of solvent and solute being multiplied or divided to have equivalent volumes that can be compared → Solution 1 is  2 : 50 X 6 = 12 : 300, Solution 2 is 4 : 100 X 3 = 12 : 300, Solution 3 is 5 : 150 X 2 = 10 : 300.
• States that solution 3 is least concentrated because when solutions 1 & 2 are made equivalent to solution 3 they have more solute than solution 3.

STUDENT RESPONSE EXAMPLES

I could tell Julie that solution #3 is the least concentrated.  I know this because solution 1& 2 have 2 spoons per evey 50mL of water. 

Solution #3, however, does not.  If it was at least the same it would be 150mL water and 6 sponns of salt, Julie might also think

the more water, the more concentrated it will be, but concentration is the amount of material dissolved in a measure of liquid. 

So if Julie adds 2 more spoons it will be the most concentrated. Casey W.

When Julie is comparing the amount of concentration in a solution, she need to keep in mind that what really matters is the

amount of material dissolved!  Therefore she needs to keep in mind that just because solution 3 has the most water it might not

have the most concentration.  She needs to look at them as if they all had 150mL of water in the solution which means that

solution 1 would have 6 spoons of salt and that solution 2 would have 6 spoons of salt dissolved.  Which means the

solutions 1 & 2 have equal and the most amounts of concentration compared to solution 3.  So Julie is wrong. Taylor H.

Actually, solution 3 has the least amount of concentration.  This happens because you could see solution 1 & 2 have equal concentration. 

They have equal concentration because if you doulbe the amount of water and salt they would be identical.  Also, you can seea pattern. 

Since 50mL of water + 2 spoons of salt and 100mL of water + 4 spoons of salt are equally concentrated; you can see that if you

add 25mL + another spoon of salt, the solutions' concentrations can be equal if you fallw the pattern.  If solution 1 & 2 are

equally concentrated, solution 3 would have to have 6 or more spopons of salt with the same amount of water.  Amy K.

I think that Julie is incorrect because, just because the third cup had more salt and more water, does not make it more concentrated.

              Also, concentration is the amount of material that dissolves in a measure of liquid.

So, just because you added more salt and water to cup number three doesn’t mean that the most material is dissolved in it.

To really find out what cup is more concentrated you need to make all of the amounts of water the same like this. 

After you’ve done that you need to multiply each of the spoonfuls by as many as you multiplied the amounts of water by.

Then, see which cup has the highest amount of spoonfuls.

As you can see cup #1 and 2 are more concentrated than cup # three.

This is what I can tell Julie about concentration.  Josh L.

              Julie is wrong.  Solution three is not the most concentrated.  Because there is more water so that solution is actually dilute:  to make a solution less concentrated, usually by adding more water.  The most concentrated solution are both of the other solutions.  They are both concentrated (the amount of material dissolved in a given amount of liquid) because solution one has half the amount of water but half the amount of salt as well, and solution two has double the amount of water and salt.  They are both the concentrated solution because as you go from fifty mL to one hundred it doubles in salt.  So every fifty mL of water you have two spoons of salt.  But on the last cup when you go up fifty mL you only added one more spoon.  So number three is dilute and number one and two are concentrated.  Tom J.

              Julie is wrong in saying the solution 3 is the most concentrated.  I would tell her that just because solution 3 has the most spoons of salt and the most water doesn’t necessarily mean that it is the most concentrated.  You see, before you can compare concentration of a solution, the volumes of the solvent have to all be the same.  The given volumes are not the same so by dividing their ratios of salt to water to fractions and then finding their equivalent fractions with the same denominators as each other, we can clearly see that solution 1 & 2 have the same concentrations and both have a great concentration than solution 3.  Concentration is the amount of material in a given amount of liquid.  So it really doesn’t matter if a solution has the most water, it matters how much salt & water it contains with the same volume as all of the solutions.   Kelli B

              Concentration is the amount of material dissolved in a given amount of liquid.  That means that just because on solution has the most solvent and solute, that doesn’t make that solution most concentrated.  You can figure out concentration either by percentage or ratios.  The most concentrated solution will be the solution with the highest percentage or ratio.

              In Julie’s case she would want to figure out the ratios of salt to water which are:  two spoons of salt to fifty mL of water, four spoons of salt:one hundred mL of water, and five spoons of salt:one hundred-fifty mL of water (2:50, 4:100, 5:150)  You can’t compare the data when the last number isn’t the same so you have to change them so that you can compare the (12:300, 12:300, 10:300).  The solution with the lowest ratio is solution three which is the solution that Julie picked.  Therefore, Julies is wrong and the most concentrated solutions are solution one and solution two.