My mtb chain snapped twice in one week?

I got my bike for christmas, its not a mtb bike its a dirt jump bike but yea, i thought more people would be willing to help me for some reason if i put mtb, but anyway, its not crappy, its this onea href="http://www.google.co.uk/imgres?imgurl=http://www.jejamescycles.co.uk/product-images-large/scorpion-awe-jump-street-bike-55321.jpg&imgrefurl=http://www.jejamescycles.co.uk/scorpion-awe-jump-street-bike-id55321.html&usg=__sq74wpHmd--FF1N2xiiwSzoVQL8=&h=372&w=600&sz=37&hl=en&start=0&sig2=qHteZJqopeNI4i8r_shMPA&zoom=0&tbnid=UThtMql-hAUQcM:&tbnh=84&tbnw=135&ei=lhM6TfbEHYGEswaOvvn0Bg&prev=/images%3Fq%3Dscorpion%2Bdirt%2Bjump%2Bbike%26um%3D1%26hl%3Den%26biw%3D1131%26bih%3D484%26tbs%3Disch:1&um=1&itbs=1&iact=hc&vpx=181&vpy=169&dur=550&hovh=84&hovw=135&tx=116&ty=65&oei=lhM6TfbEHYGEswaOvvn0Bg&esq=1&page=1&ndsp=10&ved=1t:429,r:0,s:0its" rel="nofollow"http://www.google.co.uk/imgres?imgurl=ht…/a a good bike, but the chain snapped twice in one week, all i want to know is could i have done this?, it has 3 front gears and 7 or 8 at the back, first time it happend, i just went to wheelie it and the second time, i just shifted gear, please help :) oh and also, are dirt jump bikes sutible for tracks like dalby forest?? i know theyre called 'DIRT JUMP' but still i wanna make sure, thanks guys :)