3.2 Water Flashcards
What does it mean when a molecule is polar?
It has regions of negativity and regions of positivity
What is a hydroxyl group?
O + H bond covalently. OH group is slightly polar - O has more electrons than H.
How are hydrogen bonds formed?
When polar molecules interact with each other, + and - regions of the molecule attract each other + form H bonds
Describe the property of hydrogen bonds.
Weak - constantly break and reform in water molecules
Do hydrogen bonds occur in small numbers or high numbers?
High numbers
Why is water liquid at room temperature?
Due to H bonding between water molecules.
- It takes lots of energy to increase water’s temp. + cause it to evaporate
What happens to water when it freezes?
Water becomes less dense when it freezes.
Why does water become less dense when it freezes?
Below 4°C, H bonds fix positions of polar molecules slightly further apart than the average distance in the liquid state.
- This produces a giant, rigid open structure, with every O atom at the centre of a tetrahedral arrangement of H atoms.
This results in a solid less dense than liquid water.
So ice floats.
Why does water move as one mass?
The molecules are attracted to each other - cohesion
How does water have adhesive properties?
Water molecules are attracted to other materials
What creates a skin surface tension of water?
Due to water molecules being more cohesive to each other than to air
