will a pen or pen cap float in water ?

1. We can say something will float or sink in water ,if we know that its is either having more or less density than water.
2. Density is directly related to mass of a substance. So those things which are heavier than water will sink in water. Like a pen,as it has a plastic body and a refill in it,its weight is more as compared to that of cap which has air pockets and its is lighter than water. 
3. Thus , a pen cap floats but the pen sinks in water.