We're actually learning propigation of error in my chem class, but it seems to be used equally as much in Physics/Stats.

My teacher showed us two methods of doing it:

REAL Method (Addition/Subtraction):
square root[(error absolute 1)^2 + (error absolute 2)^2 +...(error absolute n)^2]

"Our School's" Method:
(Error absolute 1) + (Error absolute 2) +... (error absolute n)

Real Method (Mult/Div)
square root[(error % relative 1)^2 + (error % relative 2)^2 + ... (error % relative n)^2]

"Our" Method:
(Error % rel 1) + (error % rel 2) + ... (error % rel n)

He also has written
Absolute error/magnitude x 100 = Error % relative?

After doing most of a problem out, we have this:

1.0(sub 8) +/- 1(sub 8) %
We divide that by 100 to get rid of the percent and get
1.0(sub 8) +/- .18 REL error

I'm not sure what to do next, but we end up getting
1.0(sub 8) +/- 0.1(sub 9) which gives us an answer of 1.1 +/- .2 g/mL

How do I get from relative error to absolute error? In other words, what happened between the part where I got the relative error, and the part I don't know how to do?

To get from relative error to absolute error, you can use the formula:

Absolute error = Relative error x Value

In your case, you have calculated the relative error as 0.18. To find the absolute error, you need to multiply this value by the corresponding value from your problem, which is 1.08 g/mL.

Absolute error = 0.18 x 1.08 g/mL = 0.1944 g/mL

Now you have the absolute error, which represents the uncertainty in your measurement. This means that the actual value could range from 1.08 - 0.1944 = 0.8856 g/mL to 1.08 + 0.1944 = 1.2744 g/mL.

So your final result, taking into account the uncertainty, is 1.08 +/- 0.1944 g/mL. You can simplify this as 1.08 +/- 0.19 g/mL (significant figures rounding).

Note: Absolute error is usually expressed with the same number of significant figures as the measurement itself.