Building a rocket for my science fair project?

well...im TRYING to build a rocket for my science fair project..but I really dunno howw!

im in 7th grade and I want to build it outa household items, if possible.

tell me any suggestions!!

ok I think I can help you out on this one although its not a real fire exhausting rocket but its a simple fun rocket
Materials:
2liter bottle of soda
airpump
cardboard square
water
paper
tape

ok so you have to make a hole in the bottle cap in order
to pump in the air and the cardboard is just to like make it seem like a rocket you know just put triangle shapes on the sides and get a regular piece of paper and form it into a cone and tape on the bottom of the bottle.
Next you fill the bottle up halfway with water then insert the bicycle pump and I hope you made the hole so it'll fit the pump exactly anyways start pumping the air and the pressure should make the bottle explode out of the pump and you might get wet depends on how far away you are from the rocket and BAM! project A+