Why does the hydroxyl group make this substance more soluble in water?
Water, by the physical arrangement of it's atoms, has a dipole associated with it. Oxygen's electronegativity essentially leaves Hydrogen without any electrons, creating a positive field near the hydrogen and a negative field near oxygen. The same case occurs with the hydroxyl group, and then these dipoles more readily interact.
This integral is impossible... help...?
There are a few ways to deal with tricky integrals like these. First, we try to make this new problem look like an old problem. We can do this with integration by parts, algebra, u-substitution, or trig substitution. Sometimes, you might have to get creative.
Why does the science section give me so much information when the questions don't require that much depth?
Part of the design of the science section of the ACT is to attempt to overwhelm you with so much information, but there is a method I use when trying to make sense of it all. A few of the questions can be answered simply by looking at the graphs indicated. Questions that ask about the experiment can be put into context of the place they appear in the background information, and then you can find the answer from here.