water Flashcards
in water, which atom’s nucleus has electrons closer to it and why?
oxygen because it has more protons in the nucleus which means that there is a greater force of attraction between protons (in nucleus) and electrons(in shells)
in water, what charge does the oxygen atom have?
slightly negative (s-)
in water, what charge do the hydrogen atoms have?
slightly positive (s+)
what is a hydrogen bond?
the electrostatic attraction between a slightly positive charge on the atom of one molecule and the slightly negative charge of a different atom
which properties of water do we only need to know the basics for?
transparent
low viscosity(runny)
adhesion
non-compressible
which properties of water are required to know at alevel?
cohesive
good solvent
metabolite
high specific heat capacity
high latent heat of vaporisation
why does water have a high specific heat capacity?
- many hydrogen bonds between water molecules
-lots of energy is needed to overcome these many bonds
-this happens first before energy can be transferred to the actual water molecule to increase the kinetic energy and heat the water
what is the phrase which says that water helps maintain a stable temperature which is an advantage for living things?
water buffers temperature changes
why is water buffering temperature changes important for living things?
it keeps temp inside a living thing stable so provides the optimum temperature for reactions and enables thermoregulation
what is specific heat capacity?
the amount of energy required to raise the temperature of one gram of a substance by one degree
what is latent heat of vaporisation?
the amount of heat energy required to change the state of a substance from a liquid to a gas
why is the latent heat of vaporisation of water high?
because a lot of energy is required to break the many hydrogen bonds between molecules
what is sweat made from?
water and ions
how is sweat able to evaporate?
water molecules absorb heat energy from the body. heat energy breaks the hydrogen bonds and the molecules have more kinetic energy so evaporate
what is the benefit to living things that sweat?
evaporation of sweat has a large cooling effect- preventing rises in body temperature so enzymes don’t denature and chemical reactions occur at the optimum rate
why does the evaporation of sweat have a large cooling effect?
a lot of energy is removed from the body in order to break the hydrogen bonds in the water molecules of sweat so it can evaporate
what is a solvent?
a substance that can dissolve another substance (a solute)
what are polar substances?
substances with a charge (positive or negative)
what kind of polar is water and why?
dipolar because it has both a slightly positive and negative charge
why can’t water dissolve lipids?
fats are non polar
what are the two benefits or water being a good solvent for living things?
- substances dissolved in water can be transported around the body/structure
- it provides a medium for chemical reactions to take place (collisions=reactions)
what is a metabolite?
a reactant or product of a metabolic reaction
what is a condensation reaction?
a chemical reaction that joins two molecules to form a single molecule, releasing a smaller molecule (e.g. water)
what is a hydrolysis reaction?
a reaction where a molecule of water breaks one or more chemical bonds
what is cohesion of water?
one water molecule ‘sticks’ to the next via hydrogen bonding
explain why water is cohesive?
hydrogen bonds form between water molecules due to the slightly positively charged hydrogen atoms of one molecule being attracted to the slightly negative charged oxygen atom of a second molecule
explain why water is a good metabolite?
water can be a reactant in a chemical reaction because the bonds in the water molecule can break and the atoms can bond with other atoms- water can also be a product that is made in chemical reactions
explain why water is a good solvent?
can dissolve polar substances because it too has polarity.
For example, the s+ charge on the hydrogen atom allows water molecule to be attracted to s- charges.
An ion would therefore become surrounded by water and be dissolved
why is water buffering temperature changes important for aquatic organisms?
the temperature of water they live in does not change rapidly- temp more stable than air
how can water having a high latent heat of vaporisation be important for plants?
transpiration of water (evaporation of water from leaves) cools plants
why is water being cohesive important for xylem vessels?
water molecules can form a continuous column of water so mass flow can occur. If one water molecule moves then the other water molecules will flow with since they’re joined via h bonds - therefore there can be bulk transport of substances down pressure gradients
so mass flow of water from roots to leaves in xylem
how does surface tension of water enable small animals to walk on the surface of water?
surface tension of water occurs because the top layers of water molecules do not have any water molecules above them to which they can be attracted - there is a net attraction downwards and surface tension produced supports body of an insect
give an example of where water is used as a metabolite in a hydrolysis reaction?
ATP is hydrolysed to release the energy for the cell’s activities
give two examples of where water is used as a metabolite in a condensation reaction?
when amino acids are joined together to produce proteins
join ADP and Pi to make ATP during respiration
give examples of how substances dissolved in water can be transported?
blood plasma is mainly water and dissolved within this water are glucose, ions, carbon dioxide , urea etc; when blood flows these dissolved substances are transported
plants transport dissolved substances in water of xylem.
