Why does plastic and wood float on water?

Question

The usual answer is that they are less denser than water. How is that solids are less denser than liquids?

Answer 1

It depends upon how the molecules are packed....usually the solid form of a substance is more dense becuase of closer packing than its liquid form...but even to this there are exceptions....Ice floats on water when chemically both are water
so one floating on the other means that the first one is less dense.
state of a substance depends upon not only the packing but more importantly the bonds that hold them together...ie the type of interactions among fellow molecules.
in Ice extra bonds( hydrogen bonds) are formed that make them more rigid but at the same time formation of the bonds causes the molecules to acquire a larger but fixed distance and thus decreasing the density...
hope u understood.
so being solid does not always co-relate with being more dense..

Answer 2

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Water's density is not 1. Anything that floats in water, does so because it's unit density is less than water. That is, a unit volume of X object has less mass (and weight) than the same unit volume of water. Basically, objects sink into the water until they displace (take the place of) a volume of water equal to their own weight. If the entire object displaces a volume of water which weighs less than the object (a stone or a lead weight, for example) the object will sink. Which explains why a coin will sink the the bottom of a well, but a plank of wood or plastic bottle of water will float. The coin is more dense than the water, which is more dense than the wood or plastic bottle of water. If you put water in a metal bottle, it would sink. If you had one bucket full of water to the brim, and put a plastic cup on top it would float. Same thing with ice. Some water would displace with the ice. But if you tried to add another cup of water it wouldn't float because the densities are the same. Water can't 'float' in water, so it would just displace its volume (i.e. one cup) and spill over.

Answer 3

plastic is waterproof and no water and be absorbed to increase its weight.
wood has more air trapped in it and as air is less dense than water, wood floats on water.
both wood and plastic are less dense than water and therefore can float on water.

Answer 4

Archimedes' Law - Archimedes' principle is the fundamental natural law of buoyancy, first identified by the Greek mathematician and inventor Archimedes in the 3d century BC. It states that any object floating upon or submerged in a fluid is buoyed upward by a force equal to the weight of the displaced fluid.

This buoyant force is caused by the weight of the fluid, which causes the fluid pressure to increase steadily with increasing depth from the surface. Any submerged object is subject to a greater pressure force on its lower surface than on its upper surface, creating a tendency for the object to rise. This tendency is counteracted by the weight of the object, which will sink if it is heavier than the surrounding fluid and will rise if it is lighter. If the object weighs the same as an equivalent volume of the fluid, it will be in equilibrium and remain motionless. Buoyancy may be thought of as the density of a fluid relative to the densities of objects submerged in it

Answer 5

linlyons is right

There are types of wood that don't float - ironwood.
There are dense plastics that don't float.

Answer 6

Try Styrofoam

Answer 7

they take up a lot of space for their mass.

density = mass/volume

if it has low mass and high volume, then the density will be smaller. in this case, it's small enough to be smaller than the density of water.

Answer 8

the elements that make certain wood or plastic is lighter than the H2O elements

Answer 9

They are LESS DENSE than water!

Answer 10

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