Alkali and current are words usually used in science. As a science student, you will need to master a large new vocabulary in order to be able to discuss, understand and write about scientific topics. As a student of English, you should also remember the terms and how to spell them!
For every science topic you learn, there will be a specific list of vocabulary to remember. "Alkali" is relevant to chemistry and discussions of any substance's pH, but "current" is relevant to work with electricity and thus physics. In biology you will need to remember the correct terms for circulatory systems, respiration, reproduction, genetics, micro-organisms, etc. In physics, you will need to learn the vocabulary necessary to discuss light, forces, energy and motion, among other topics, and in chemistry, you should know the correct terminology to describe materials, the structure of atoms, the elements, and different types of changes and reactions.
Each of these areas has a large specialist vocabulary, so the sooner you get to work learning the correct terminology, the better!
Test your knowledge of words used in science by playing this quiz on the subject.