Water Flashcards
Why is a water molecule described as dipolar?
Oxygen atom has a partial negative charge and hydrogen atoms have partial positive charges, so molecule has both positive and negative poles
What two features gives water it’s unusual properties?
- hydrogen bonds
- dipolar molecule
How does the hydrogen bonding between the molecules occur?
Positive pole of one water molecule is attracted to the negative pole of another - attractive forces between opposite charges is a hydrogen bond
Is a hydrogen bond weaker or stronger than a covalent bond?
Weaker (about 1/10th the strength)
Why do molecules stick together?
Numerous Hydrogen bonds between molecules.
How does the tendency for water molecules to stick together affect the specific heat capacity?
Means it takes more energy to separate them than would be needed if they weren’t bonded to one another - so boiling point is higher than expected.
What state would water be in without hydrogen bonding?
Gas
Does water have a high specific heat capacity?
Yes
How does its specific heat capacity make aquatic environments temperature stable?
It’s high specific heat capacity allows it to act as a buffer against sudden temperature variations.
Why does water also buffer organisms against sudden temperature changes? (Especially in terrestrial environments)
Organisms are mostly water.
How does hydrogen bonding affect the latent heat of vaporisation?
It makes it very high
How does water’s latent heat of vaporisation give effective means of cooling for the body?
Evaporates water via sweat from mammals and so body heat is used to evaporate this water.
What is cohesion?
The tendency of molecules to stick together
Why does water have large cohesive forces?
It’s hydrogen bonding.
What does it’s cohesive forces allow in plants’ xylem vessels?
Allows water to be pulled up a tube as molecules stick together
What is surface tension?
Where water molecules meet air they tend to be pulled back into the body of water rather than escaping it.
Is surface tension a force?
Yes
Why is water strong enough to support small organisms such as pond skaters?
The water surface acts like a skin and is strong.
What does the fact that up to 98% of a jellyfish and mammals are typically 65% water demonstrate?
Water is the main constituent of all organisms
What are 3 reasons water is very important?
1) main constituent of living organisms
2) where life on earth arose
3) environment where many species live
What are 3 used of water in metabolism?
1) used to break down complex molecules in hydrolysis/ is produced by condensation reactions
2) chemical reactions take place in aqueous medium.
3) is a raw material in photosynthesis
For what 4 things does water act as a solvent for?
1) gases such as Oxygen and CO2
2) wastes such as ammonia and urea
3) inorganic ions and small hydrophilic molecules (E.G. AAs, ATP…)
4) enzymes whose reactions take place in solution.
What does water not easily able to be compressed mean?
Water can provide support - for example the hydrostatic skeleton of animals such as earthworm and turgor pressure of herbaceous plants
What does water being transparent mean? (2)
Aquatic plants can photosynthesise
Light rays can penetrate the jelly like fluid covering that fills the eye so light can reach the retina
