If all planets came from the same cloud and elements,why aren t all planets the same?

I asked my science teacher this and he said it was because of the order they came out, however i do not understand. If you do a science experiment mixing two elements(or compounds),you will always get the same result as long as all of the constants needed are the same. So if all planets came from the same cloud how... show more I asked my science teacher this and he said it was because of the order they came out, however i do not understand. If you do a science experiment mixing two elements(or compounds),you will always get the same result as long as all of the constants needed are the same. So if all planets came from the same cloud how could there be gas and rocky planets?
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