Squash vs. quash
Wrong: Saddam Hussein squashed the rebellion.
Right: Saddam Hussein quashed the rebellion.
To squash is to crush, flatten, or pulp. To quash is to suppress, quell, or subdue. Although a dictator might be said to crush a rebellion, he doesn't literally press it into a flat mass to squeeze the juice out of it. The correct term for ending a rebellion, or to deny a legal motion, is to quash it. Although the difference in meaning between these two words may seem trivial, as Mark Twain once said: “The difference between the almost right word and the right word is really a large matter—it's the difference between the lightning bug and the lightning.”
Purposely vs. purposefully vs. on purpose
Right: You did that purposefully.
Right: You did that purposely.
Right: You did that on purpose.
Purposely means intentionally (as opposed to accidentally) or on purpose. If you do something for an express purpose, you do it purposefully. Both expressions are correct, but be sure you use them correctly.
More next time.