2.2 Water Flashcards
What are the uses of water because of its liquidity at room temperature ?
• provide habitats for living things in rivers, lakes and rivers e.g fish
•form a major component of the tissues in living organisms
• provide a reaction medium for chemical reactions
•provide an effective transport medium e.g in blood and vascular tissue
What are the properties of water ?
•High specific heat capacity
•High latent heat of vaporisation
•Density
•Cohesion and surface tension
Because ice is less dense than water it means…
•Ice floats
•Ice can act as a habitat for organisms e.g polar bears to breed
•Ice insulates the water below and prevents it from freezing —-> this means that organisms can continue to live in the water under the ice
Why is water a good solvent?
-because water is polar —> enables water molecules to attract solute molecules
What are the roles of water?
*Excellent solvent
*Plays a important role in metabolic reactions
What does water’s high specific heat mean?
We have to put in or take out a large amount of energy to change the temperature of water
—-> Allows water to act as a habitat for aquatic organisms (they would not be able to function if the temp of watt changed rapidly eg on cold or hot days)
What happens when water is heated?
When heated, the heat energy goes towards weakening or breaking the hydrogen bonds rather than increasing the kinetic energy of the water molecules—> this means that water acts as a buffer against rapid temperature changes
What is the structure of a molecule of water?
•One atom of oxygen covalently bonded to two atoms of hydrogen
•The oxygen molecule has a small negative charge
•The hydrogen atoms have a small positive charge—> because of these charges water is a polar molecule
What do the opposite charges mean in a water molecule?
•Water is a polar molecule
•The molecules are attracted to eachover (hydrogen bonds)
What are hydrogen bonds? (are they strong bonds?)
The forces of attraction between water molecules due to water’s polarity.
•Hydrogen bonds are weak bonds, however they are large in volume so collectively strong
What does water’s high latent heat of vaporisation mean?
Takes a large amount of heat energy to evaporate water
•This allows organisms to cool themselves without losing a great deal of water e.g sweating —-> during sweating, heat energy is used to evaporate water from the surface of the skin and this transfer of heat energy allows organisms to cool down
What does water being a good solvent mean? And how does it make it an excellent habitat for aquatic organisms ?
Lots of substances can dissolve in water e.g. both eukaryotic and prokaryotic cells contain a large amount of dissolved substances, chemicals involved in metabolic reactions such as respiration
•Bodies of water such as pond and rivers contain dissolved oxygen, used by organisms such as fish to carry out respiration——> makes water an excellent hahitat for these organisms
•Be used to transport substances e.g. -Blood plasma contains a large number of dissolved substances including carbon dioxide, mineral ions
-Water in the xylem contains dissolved mineral ions such as the magnesium ion needed for plant growth
What is cohesion?
Water molecules sticking together due to the hydrogen bonds between the water molecules
•Cohesion allows long collumns of water to travel in the xylem tube
•Causes surface tension where water meets air
How is water an ideal transport medium in plants?
•Cohesion allows long collumns of water to travel in the xylem tube
•Water in the xylem contains dissolved mineral ions such as the magnesium ion needed for plant growth
Why is surface tension useful? (what is it)
-where water meets air
• Surface tension is useful as it allows the surface of water to act as a habitat e.g insects such as pond skaters
