Science Notes

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1. The properties of water are essential to all life on Earth. a. Outline the significance of the labeled parts of this diagram, showing the attraction between three water molecules. | w.| Negative charge oxygen atom|

| x.| Positive charged oxygen atom|
| y.| Weak hydrogen bond between δ+ and δ- parts of neighboring water molecules. | | z.| Strong hydrogen bond |
| δ-| Slight negative charge as large oxygen atom attracts shared electrons closer to itself than the hydrogen atom. | | δ+| |

Extension: at this point you might want to consider how ionic and covalent bonding work, in order to really understand how the slight positive (δ+ ) and slight negative (δ- ) charges are generated. 2. Water has many properties which are essential for life. Complete the table below.

| Explanation | Significance to living things|
Thermal Properties| When a solid changes to a liquid and a gas more heat is added. This is quite hard as to change phases you have to break the hydrogen bonds and it takes a lot of energy to change from one phase to another. | Water’s thermal properties means that it has the ability to cool us down. When sweat evaporates off our body it takes heat away from our body. | Cohesion| Water’s polar nature makes water “sticky”. This happens because the water molecules stick together due to the hydrogen bonds. | If water were not “sticky” water would not form droplets. In addition, cohesion allows plants to transpire and pull water up to the leaves.| Solvent Properties| Again due to water’s polar nature water is known as the “universal solvent” and as a result is it good at dissolving substances. Polar substances are hydrophilic and non-polar substances are hydrophobic. | Water’s solvent properties mean that it can transport waste through veins and arteries. It enables trees to transport gases and solutes as well. | (include uses as a coolant, medium for metabolic reactions, transport medium)

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