Why does water change in volume as its temperature changes?

Answer 1

The density of a liquid is determined by the mean molecular separation distance D (how far apart the molecules are, on average). The actual size of each molecule changes very little with temperature, unless a chemical reaction occurs. D, in turn, is determined by a balance between molecular attraction (molecules in a solid or liquid invariably have this; thats why they condense) and repulsion due to their relative motion (they bounce off of each other). Higher temperature means their relative velocities during collisions are usually higher, and collisions are more frequent, so D generally increases. There are unusual cases, though, were this general rule doesn't apply due to an unusual temperature dependence on molecular attraction near freezing. If the temperature gets too high, collisional repulsion wins out abruptly and (almost) entirely, and the liquid evaporates.

Answer 2

Under certain circumstances, volume becomes a function of pressure and atomic/molecular alignment. This is an odd example, since water actually expands when it's cooled to freezing.

But NORMALLY, the moreenergetic particles become, the more energy the impart to their surroundings. IE, they "press" harder on any enclosing boundaries (such as the wall of a balloon). This causes the encosing object to expand. The bigger it gets, the more volume (more space inside). So, once the internal pressure is higher than the external pressure, the insides arepushign harder than the outides, and the insides win, so the balloon or bubble wins and it expands.

Likewise, when it cools off, a balloon or bubble tends to contract since it's losing energy, and the constituent gas atoms are all bouncing less violently inside the balloon/bubble. Thus the outside medium is more highly pressurized and presses in, shoving the innards into a smaller space. And a smaller space has a smaller volume (same amount in a smaller space).

Hope that makes sense.

Cold = less energy = higher pressure outside = area encompassed by the innards shrinks.
Hot = more energy = more violent and energetic reation with outside = higher pressure inside than outside = innards expand.

Again, that's normally... Water and maybe a few other exotic elements or molecules have a slightly different structure and expand when they freeze, which is unusual, but due more to structure than total energy/pressure.

Answer 3

Hi. Water, like most substances, consists of molecules that vibrate due to heat energy. More heat means more vibration and this takes up more space. Actually water is kind of weird because it is densest at about 38 or 39 degrees F, not 32 deg F. So warming water from 32 to 38 causes it to shrink.

Answer 4

Water actually contracts when it gets cooler, but then expands again when it freezes. Water also expands while it gets warmer. Its all about H2O molecules and how they react to ambient heat.

This is why scientists are so concerned about global warming. As the air heats, it expands and holds onto more carbon dioxide. Believe it or not, the warming of the earth is also causing the oceans to expand, resulting in coastal flooding and erosion.

Answer 5

coz an increase in temperature increases the movement of the H20 molecules, as their bonds become weaker. Thus, they take up more space.

Answer 6

its molecules expand. Same at the body, concrete, and everything else. it allows the heat to escape faster.