Facebook – Disable Chat [Parental Controls]

Is there a way to disable facebook chat?
We have a child using it inappropriately and I think it’s best that chat be disabled. I know I can block facebook but I don’t want to do that.
PC = windows 7
Browsers installed = Chrome, IE, Firefox
thanks for any input.
Answer #1
use ad blocker plus and right click on the chat and select the ad block icon and block it that way. works for me
or ban them from the pc or block facebook if its a child dont let them on anyway.
Answer #2
I was hoping there’s a “universal” fix without configuring each browser. The child is 17
I suppose I could block other browsers from running and configure the usable one to block chat.