What dilution did I make?!?
An introduction to dilutions
Dilutions are fractions
•  When we add water to orange juice
concentrate to make orange juice for breakfast,
we are making a dilution.
•  The dilution that we have made can be
determined by the expression:
Parts of orange juice concentrate
Total parts of prepared orange juice
Preparing orange juice
If we follow the directions to make orange juice from
concentrate, we add 3 cans of water to one can of orange
juice concentrate:
Dilution:
1 can orange juice
OJ
4 cans total
H2O
H2O
H2O
OJ
The final concentration of the orange juice is 1/4 of the
original concentration
Preparing orange juice
If we like our orange juice less strong, we can add more water:
Dilution:
1 can orange juice
OJ
5 cans total
H2O
H2O
H2O
H2O
OJ
The final concentration of the orange juice is 1/5 of the
original concentration
Preparing orange juice
If we like our orange juice stronger, we can add less water:
Dilution:
1 can orange juice
OJ
3 cans total
H2O
H2O
OJ
The final concentration of the orange juice is 1/3 of the
original concentration
Note that, as the fraction representing the dilution gets smaller, the color of
the orange juice becomes lighter. This is because you are diluting the orange
juice more with additional water.
1/3 dilution
1/4 dilution
1/5 dilution
It’s easy to determine the dilution made:
The dilution is: parts of solute*
total parts of solution**
*Solute--the liquid you are diluting
**Solution--the combination of solute and water
“Parts” can be anything…
(as long as they are the same….)
A 1/3 dilution could be:
1 can solute
3 cans solution
Parts can be anything…
(as long as they are the same….)
A 1/3 dilution could be:
1 tablespoon
3 tablespoons
More commonly…
•  Parts will be some common unit of volume in
the lab:
1 mL solute
or 1 L solute
3 mL solution 3 L solution
But….
The “parts” cannot be different:
Suppose you added 1 mL of solute to enough water to make 1 L total of
solution. What dilution did you make?
1 mL is NOT correctly expressed 1L
This dilution would need to be expressed as:
1 mL
or
0.001 L
1000 mL
1 L
Note that the units
do not cancel out!
Look! The units cancel!
Either expresses a 1/1000
dilution!
Just remember….
To find the dilution--just put parts of solute over
parts of solution. It doesn’t have to be pretty!
Example:
If you add 8.3 mL of water to 1.5 mL of solute what
dilution have you made?
The total volume of solution is 1.5 mL + 8.3 mL =
The dilution is:
1.5 mL solute 9.8 mL solution
=
1.5
9.8
9.8 mL solution
Well…
That’s not a pretty dilution, but it was
easy to figure out!!!