Water Flashcards
What is H20 made up of?
1 atom of oxygen joined to 2 atoms of hydrogen by a shared pair of electrons in a covalent bond
How is water a polar molecule/a dipole? 2
- Oxygen is more electronegative than hydrogen
- The shared negative electrons are pulled towards the oxygen atom
What charge is on the hydrogen atoms in water?
A slightly positive charge - delta positive
What charge is on the oxygen atoms in water?
A slightly negative charge - delta negative
What type of molecule is water?
A dipole/polar
What is hydrogen bonding in water?
The delta hydrogen atoms are attracted to the lone pair of other oxygen atoms of the water molecules
What are the useful properties of water? 4
- Cohesive
- Solvent
- High specific heat capacity
- High boiling point
What does cohesive mean?
Molecules stick together
Why is water being cohesive useful? 3
- Helps water flow well
- Useful for transporting substances
- Makes it possible to pull water uphill e.g in xylem
Define solvent.
A liquid that other substances dissolve in
What types of substances dissolve in water? 2
- Ionic
- Polar
What type of substances don’t dissolve in water?
Non polar
Why is water being a solvent useful?
Substances for important reactions can dissolve in it to be transported
Why do ionic substances dissolve in water? 6
- Water is polar
- The hydrogen delta positive end of the water molecule is attracted to the negative ion [e.g Cl-]
- The oxygen delta negative end of the water molecule is attracted to the positive ion [e.g Na+]
- All the small charges in water add up together to equal the charge of the ion
- The ion breaks free
- Ions are hydrated, completely surrounded by water molecules and have dissolved
Give a useful ionic substance dissolved in water
NaCl - salt
What reactions is water important in?
Metabolic reactions e.g condensation/hydrolysis
Why is water cohesive?
Due to hydrogen bonds
What polar molecules are useful to dissolve in water and what makes them polar?
- Sugars - OH group
- Amino acids - NH2 group
Give a type of non polar molecule that doesn’t dissolve in water.
Lipids
How is water useful in allowing biochemical reactions to occur in cell cytoplasm?
Substances it transports are free to move around and react because they are dissolved
What do lipids require to be transported?
Proteins - they form lipoproteins
What does water having a high specific heat capacity mean? 2
- A large amount of energy causes only a small increase in temperature
- Water cools and heats up slowly
Why does water have a high specific heat capacity and a high boiling point?
Large amount of energy needed to break hydrogen bonds
Why is water having a large specific heat capacity useful for organisms? 2
- Helps them avoid rapid changes in internal temperature and maintain a steady one
- Even when external temperature varies considerably
