Water Quiz Notes

Water = molecule made of 2 hydrogen atoms and one oxygen atom(H2O). These atoms are held together by covalent bonds.

Water has special properties because it’s a polar molecule -has slightly negative and positive regions

Oxygen is slightly negative Hydrogens are slightly positive A water molecule can form hydrogen bonds (a type of Van der Waals bond) with other water molecules

Covalent bonds

Properties of water

1. Cohesion – attraction between two or more of the same molecule

e.g. water sticking to water through hydrogen bonds -creates surface tension and water droplets Surface tension created by hydrogen bonds is strong enough for water strider Hydrogen bonds create surface tension and hold water droplet together

2. Adhesion – attraction between two or more different types of molecules e.g. when water bonds to other things/surfaces using hydrogen bonds Cohesion and Adhesion in action Plants use adhesion and cohesion to move water up against gravity without using energy → capillary action

1. Cohesion – water forms a column

2. Adhesion – water sticks to the vessel elements (like a straw)

3. Water evaporates from the leaf

(transpiration) → pulls the entire water column up

3. Water is less dense than a solid

Water becomes less dense when it freezes – molecules spread out when hydrogen bonds form Ice is strong enough to break rocks → helps make soil Ice floats → keeps ponds, lakes, and oceans from freezing solids and allows life to continue under the ice

4. High Heat of Vaporization

It takes a lot of heat to change water from a liquid to a gas Evaporative cooling - water removes heat when it evaporates from a surface (e.g. sweating - helps to cool our body and maintain homeostasis)

5. High specific heat

-It takes a lot of heat to raise the temperature of water (compared to other substances) Water stores heat and helps to maintain and stabilize earths tem’s temperature.