To see if hyperthreading is ON or OFF run Task Manager (Ctrl+Shift+Esc) and click the "Performance" tab. If there are two CPU graphs then for a Core i3 it means HT is OFF. Four graphs means HT is ON.
For Word and web browsing you probably won't see any difference in performance, heat or battery life. Those types of programs are normally constrained by how fast the user can type or click links, and that's WAY slower than the CPU.
The only reason you might see a difference with hyperthreading is if the program has to use the CPU heavily. For example a web page with a 3D Flash object showing a continuously moving scene might perform better while doing other work with 4 threads instead of just 2.