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They key points covered in this video include:
1. Incompressibility of Water
2. Density of Water
3. Importance of Water Density
Incompressibility of Water
Like all liquids, water is incompressible - you can see this for yourself by squeezing full and empty plastic bottles. This feature of water is used by soft-bodied animals which don't have an endoskeleton or exoskeleton for support. Instead, these soft-bodied animals, such as earthworms, have a hydrostatic skeleton. Hydrostatic skeletons are fluid-filled cavities that prevent the earthworm from being compressed. Plants also have water in their cells to allow them to resist external forces. This prevents the plant from collapsing under its own weight. The incompressibility of water also can be used by some animals in order to move.
Density of Water
Density is a measure of how much mass a substance has in a given volume. Normally, as substances change state from a liquid to a solid, they become more dense. Water is unusual because its solid state is less dense than its liquid state. As a liquid, water molecules move past each other, constantly forming and breaking hydrogen bonds. As liquid water cools, more hydrogen bonds are formed and water becomes more dense - maximum density is reached at 4oC. As water then freezes to ice, each water molecules forms the maximum four hydrogen bonds. In order to achieve this, the water molecules need to be more spaced out in a regular geometrical structure. This results in ice being less dense than water.
Importance of Water Density
Objects sink when they are more dense than water and float when they are less dense. The density of water makes it an ideal habitat as it is dense enough to allow many organisms to float. As ice is less dense than water, it also floats on the surface. Floating ice is essential for life as: It provides a habitat for creatures who live in cold climates, It provides an insulating layer against the external cold which prevents lakes and rivers from freezing solid.
Summary
Like most liquids, water is incompressible
This allows it to be used to support soft-bodied animals and plants
This property can also be used to aid movement in some animals such as spiders
The hydrogen bonds that form as water freezes result in the water molecules in ice being more spaced out
This makes ice less dense than water so it floats on top of water
This provides a habitat for organisms that live in cold climates
It also creates an insulating layer that prevents the whole body of water from freezing, allowing organisms to survive sub-zero temperatures
11 июл 2024
