Well, today the electrician came by and fixed everything! He explained a lot about what was going on, so I figured that I'd relay some of the information so that you don't make the same mistakes that I did. I will point out that I am NOT an electrical expert--I'm a mechanical engineer for a reason--so I'll explain all of this simply because that's pretty much as far as my knowledge goes. If you have specific questions, I highly suggest you consult a professional (ehhhemm...please refer to the title of this blog post).
First off, all of the electrical wiring in a house is split up into several smaller "circuits". A circuit may include just the outlets/overhead lights in one room, or several different rooms together (each house will be totally different). Each circuit is connected its own little breaker in the main breaker box (my breaker box is in my basement, and each breaker looks like a little switch). You might have a fuse box instead of a breaker box, and in that case, each circuit will have its own fuse. When the breaker senses a problem, or you have too much of an electrical load on any given circuit, the breaker will flip "off" to disconnect the circuit and prevent any electrical damage (if you have fuses, then a fuse will blow).
This is my main breaker box! I'm pointing to one of the many smaller breakers that the main box contains (awww, look at how cute it is!). The really big breaker switch at the top turns everything off at once.
So, now that we've got that covered...
Each outlet has two plugs (one on top, one on bottom). Initially, the two plugs are linked together so that if you connect one plug to have power, then both of them have power. See that little metal tab that I'm pointing to? That's what's connecting the two plugs.
Typical room outlets only need power to one of the two plugs because they're connected with the little metal tab, which means that if one plug has power, then both plugs have power. Kitchen outlets are the exception to this rule. If you're like me, you hook up your microwave, toaster, phone charger etc all grouped together in one little corner. Electricians like to separate the little tab connecting the two plugs of an outlet so that the top plugs can be placed on a separate circuit from the bottom plugs. That way, if you DO have a bunch of appliances hooked up in one small area, you're less likely to trip your breakers because the load is being split up onto two different circuits (breakers). If this is the case, you need to break the little metal tab connecting the two plugs to separate them--there's one metal tab on each side of the outlet!--and then provide power to EACH plug on its own circuit.
I did not know about the whole "you must separate the two plugs for kitchen outlets on separate circuits" deal when I changed all of the outlets. When I attached power to both the top and bottom plugs, I was essentially giving the whole outlet twice the amount of power that it needed (because the plugs were still connected to each other). This changed our typically docile toaster into a turbo-charged maniac (it burned a bagel in 3 seconds flat--I kid you not!!). Something like this could fry a big appliance (your refrigerator would be so sad!), or start a fire (our toaster went crazy in just a few seconds...who knows what would have happened if we'd walked away for a few minutes).
I know that this isn't as exciting as a full room redo reveal, but it's super important if you're changing out outlets in a kitchen! When in doubt, call a professional--your toaster will thank you ;)