In terms of a deeper scientific reason, I am not sure, but the basic reason is quite simple. "Mud" tends to look like a mix between a solid, dirt, and a liquid, water or some other liquid. Since it is, in fact, a cross between a solid and a liquid, it has properties of both. It has certain physical and visual properties that only a solid would have, such as texture and opaqueness, but it also has physical properties of a liquid. Since it leans more towards the liquid side than the solid side, we say mud "flows" rather than saying that it "rolls" or "bounces".
Hormones travel through the body by using blood streams, such as veins. The hormones then get to the target cell by moving through the liquids surrounding the cells. They then change how the cell works, thus changing the body.
Explanation:
hope the picture above help u understand:)
The molecules in ammonia are bonded together by covalent bond; this is the type of bond in which electrons are shared among atoms in the compound. Ammonia is a polar molecule and is made up of one nitrogen atom and three hydrogen atoms. The hydrogen atom in ammonia is bonded to the three hydrogen atoms via sharing of three electron pairs, one with each atom of hydrogen. For each of the three covalent bond formed, one electron is supplied by nitrogen and one by hydrogen atom.