I would definitely expect a curve sketching question, newtons laws/gravitation/orbits are regulars, something to integrate (worst case scenario would be substitution and you can't see what you should substitute, or a integration by parts and you don't recognise it as such, doubt most places would be so harsh though). You can expect a fictitious scenario, i.e. in my Cambridge one my interviewer asked me to walk him through all the engineering considerations that need to be made when designing a bridge, a very broad question aimed at seeing how you think. Electronics/electricity is obviously a good one, but usually only on the basics but you'd be surprised how many people trip up on those.
For chem eng, I'd expect a question on thermodynamics, nothing too complex but you should have covered 1st law in physics A-level, maybe one to see if you can apply newtons laws to continuum mechanics (i.e. fluid flow), its easy but that you need to consider mass flow rates and so momentum=mv becomes mom = m[dot]v (m[dot] is mass differentiated w.r.t. time). Remember not everything comes in the form of a mathematical question, it might just be drawing diagrams and talking about it and righting down bare equations without the algebra.
The big one they can give you if they want to stretch you is deriving the escape velocity of earth starting with the universal gravitation law F=GMm/r^2. The key is to spot that this can be written in differential form from dW = F dr, sub F in, integrate between radius of earth and infinity, and then equate the remainder to eqn of K.E. (= 0.5mv^2), rearrange, substitute in values and bada bing, out pops V. This is a classic because it draws in a lot of aspects of maths and physics together, which is what engineering is at the end of the day.
I suspect most of the above would be irrelevant unless you have an Oxbridge/Imperial interview, I've heard Imp are making a move into doing Oxbridge type interviews, though back in my day it was just simple state Newtons laws, why engineering, why Imperial blah blah.