Water Flashcards
What are the five key properties of water?
- It is a metabolite
- It is an important solvent in reactions
- Has a high heat capacity - buffers temperature
- Has a large latent heat of vaporisation
- Cohesive
Why is water being a metabolite an advantage?
- in condensation and hydrolysis reactions
- in hydrolysis, requires a molecule of water to break a bond
- in condensation reaction, releases a molecule of water as new bond forms
What is the advantage of water being an important solvent in reactions?
- dissolves solutes such as salt as water is polar the slightly negative atom is attracted to the positive ion
- transport of inorganic ions in blood plasma
What is the advantage of water having high heat capacity?
- buffers temperature which is useful to animals as water temperature doesn’t change rapidly
- hydrogen bonds give to water
- takes lots of energy to heat
What is the advantage of water having a large latent heat of vaporisation?
- provides cooling effect with loss of water through evaporation
- water evaporates and carries away heat energy when hydrogen bonds holding water break
- allows molecules or water on surface to escape as gas
- take a lot of heat
What is the advantage of water having strong cohesion?
- supports water columns and provides surface tension
What is cohesion?
- water molecules are attracted to one another
What is surface tension?
- water molecules are more attracted to each other than the air
What does it mean that water is a metabolite?
- water is involved in many reactions such as photosynthesis, hydrolysis and condensation reaction
- 90% of plasma in blood is water and cytoplasm cell is largely composed of water
What does it mean that water is a good solvent?
- many substances dissolve in it
- polar or charged molecules dissolve readily in water due to the fact that water is dipolar (slightly negative and positive)
- slightly positive charge on hydrogen atoms attract negative ions solutes and slight negative charge in oxygen atoms attract any positive ions in solutes
- so many essential polar substances dissolved in water enabling them to be transported easily around animal and plants either in the blood or xylem to cells they are needed in inside of the organism
What are polar molecules described as?
- hydrophilic (attracted to water)
Which molecules cannot dissolve in water?
- non polar molecules such as lipids and are described as hydrophobic
Hydrophobic meaning
- repelled by water
What does it mean that water has a high specific heat capacity?
- a lot of energy required to raise the temperature of water
Why does water have high specific heat capacity?
- some of the heat energy is used to break the hydrogen bonds between water molecules
Why is high specific heat capacity useful to organisms?
- Temperature of water remains relatively stable even if surrounding temperature fluctuates significantly
- so internal temperatures of plants and animals should remain relatively constant despite the outside temperature due to the fact a large proportion of the organism is water
Why is high specific heat capacity important?
- so enzyme do not denature or reduce in activity with temperature fluctuations
- to provide a stable environment in terms of temperature for aquatic organisms
What does it mean that water has a large latent heat of vaporisation?
- a lot of energy is required to convert water in its liquid state to a gaseous state
Why does water have a large latent heat of vaporisation?
- hydrogen bonds as energy is needed to break the hydrogen bonds between water molecules to turn it into gas
Why is large latent heat of vaporisation advantageous?
- water provides a significant cooling effect
- when human sweat they release water onto their skin
- large amounts of heat energy from the skin is transferred to the water to evaporate it, removing a lot of heat and cooling the organism
What bonds cause cohesion?
- hydrogen bonds
Why is cohesion advantageous?
- due to water molecules sticking together when water moves up the xylem in plants due to transpiration it is as a continuous column of water
- easier to draw up a column rather than individual molecules
- provides surface tension to water
- enables small invertebrates to move and live on the surface, providing them a habitat away from predators within water
Water is polar. What does polar/dipolar mean?
- there is an uneven distribution of charge
- Oxygen is slightly negative and Hydrogens are slightly positive
What bond is between the hydrogens and the oxygen?
- covalent bond
What is cohesion due to?
- polarity of water
Why is frozen water less dense than liquid?
- as water freezes, it expands and floats
What is an advantage of frozen ice layer on water?
- insulates the water below it so it doesn’t freeze
Why is water transparent?
- allows photosynthesis to occur as light is let through
