Water Flashcards
What is the structure of a water molecule?
- Water is a (di)- polar molecule.
- Has unevenly distributed charge (due to oxygen atoms being slightly negative and hydrogen atoms being slightly positive.
Where are hydrogen bonds formed in water molecules?
- Hydrogen bonds are formed between the slight negative oxygen atom (on one water molecule) and the slightly positive hydrogen atom (on another water molecule.)
What is meant by di- polar molecule?
- Di- polar molecule has two different regions that are charged.
What is meant when we say water is a “metabolite?” Examples of reactions water is involved in?
- This means that water is involved in chemical reactions (remember metabolism = sum of chemical reactions. )
- Examples: photosynthesis, hydrolysis, condensation reactions.
() - extra info for clarification
Why is 90% of the plasma in the blood water and why is the cytoplasm mainly composed of water?
- Because water is a metabolite (involved in chemical reactions. ) A good supply of water is necessary to be present in the body for the chemical reactions that occur in body (ie. hydrolysis/ condensation.)
What are the 5 key properties of water?
1.) It is a metabolite in many metabolic reactions.
2.) It is an important solvent in which metabolic reactions occur (metabolic reactions occur quicker in solution.)
3.) Has a high heat capacity, buffering changes in temp.
4.) Has a large latent heat of vapourisation - providing a cooling effect.
5.) Has strong cohesion between water molecules.
What do we mean when we say water is a good solvent? Why is water a good solvent (think in terms of its structure?)
- Many polar (ie. charged) molecules dissolve easily in water due to fact it is dipolar.
- Slight positive hydrogen will attract any negative ions in solutes.
- Slight negative oxygen will attract any positive ions in solutes.
- This will separate the solute/ dissociate the ions in the compound - and the solute will be dissolved.
What are polar molecules that can be dissolved in water often referred to as being?
- Hydrophillic (attracted to water.)
What are non-polar molecules (that can’t dissolve in water) often referred to as?
- Hydrophobic (repelled by water.)
Why is it useful in humans and plants for water to be a good solvent?
- Means that essential polar molecules can be transported around the body easily in plasma/ blood (in humans.) to cells needed.
- Plants –> sugars can dissolve in water in phloem/ mineral ions can dissolve in water in xylem - transporting polar molecules to required cells.
Why is it useful that water has a high specific heat capacity?
- This means the temperature of water remains relatively stable, even if surrounding temp changes.
- Internal temp of plants/ animals remain relatively constant despite outside temp (large amount of water in organisms.)
- It also provides a stable temperature for aquatic organisms.
What do we mean when we say water has a high specific heat capacity? Why does water have a high SHC?
- This means a lot of energy is required to raise the temperature of water.
- This is because some of the heat energy is used to break the hydrogen bonds between water molecules (rather than increasing the temperature.)
Why is it important that the temperature of animals/ plants remains relatively constant?
- Important so enzymes don’t denature (high temp) or reduce in activity (low temp) with temperature fluctuations.
What is meant when we say water has a large latent heat of vapourisation? Why does water have a large latent heat of vapourisation?
- This means a lot of energy is required to convert water from a liquid state to a gaseous state.
- Due to hydrogen bonds between molecules, a lot of energy is required to break the hydrogen bonds between water molecules/ convert the water into a gas.
Why is it useful for humans that water has a large latent heat of vapourisation? Explain the example of sweating….
- Provides a cooling effect.
- Ie. humans sweat/ release water onto skin. Large amounts of heat energy can be transferred from the skin to the water (before the water evaporates.)
- So, large amounts of heat energy are transferred to environment when the water evaporates but this occurred with little loss of water.
