A1.1 - water Flashcards
why do living things need water ?
for a solvent, metabolite, thermoregulatory and habitat.
how did water help the earth begin?
it provided an energy and chemical rich environment where naturally occurring organic molecules can develop. water could also support the development of primitive and compartmentalised cells.
how are living organisms dependant on water?
water makes up cytoplasm ( which gives the cell structure and support) water also forms the fluid of inside organelles, facilitates transport in and out of cells and provides a habitat for many organisms.
what makes the covalent bonds between water molecules polar?
the uneven sharing of electrons create a polarity between the negatively charged oxygen and the positively charged hydrogen atoms.
why does hydrogen bonding occur between water molecules?
because of the polarity, oxygen has a negative charge but hydrogen has a positive charge, because opposites attract a weak covalent bond is formed.
what is electronegativity influenced by ?
the number of protons in the nucleus and the number of shells.
what happens to the electrons when a shell is less then half full?
they lose their electrons thus they have low electronegativity.
what happens to electrons when a shell is more then half full?
they tend to gain electrons thus they have a higher electronegativity.
why do the poles occur ? ( refer to oxygen and hydrogen electronegativity)
oxygen has a higher electronegativity then hydrogen thus it attracts more of the shared electrons . this uneven distribution results in the negative charge on the oxygen atoms because when you gain electrons you get a negative charge.
are hydrogen bonds permenant?
no, they can break and reform.
how many bonds can water molecule form with other water molecules?
they can form 4 hydrogen bonds in a tetrahedral form .
why do water molecules form hydrogen bond with other water molecules ?
because the dipoles are attracted to each other.
why does cohesion of water molecules occur ? and what does this mean ?
when the negative charge and opposite charge meet because they are attracted. the water molecules stick to each other. this means water can be transported under surface tension.
what is surface tension ?
when water molecules stick together on the surface of water. surface tension must be broken when an object touches the water .
what adaptations do some organisms have to avoid them breaking surface tension?
small body mass, large surface area and water repellent surfaces.
how do animals avoid damage through surface tension?
many diver birds are streamlined to avoid friction when breaking surface tension.
what is capillary action ?
the ability of water to flow against gravity in a narrow space.
how does capillary action work ?
the water can form bonds with a surface because it can partake in adhesion.
why can capillary action work better in different types of soil?
it is higher in clay soils as they have many small charged particles whereas sandy soils have fewer larger particles with big air gaps between them which water can flow through easily.
how does capillary action occur in soil?
as plants remove water from the surface layers of the soil the water is then replaced through capillary action.
how do plants use capillary action?
they use it to move water into cells , as water moves through the xylem the cellulose fibres can pull water into them. this way water can move from cell to cell and transport dissolved nutrients.
why is capillary action used in soil and not osmosis?
Osmosis requires different water concentrations and a partially permeable membrane. It can occur across the tissues of the cells and the cells of the leaves because there is a membrane between each cell or tissue. Osmosis cannot happen within the soil as there is not a partially permeable membrane for osmosis to occur within.
what does hydrophilic mean ?
Hydrophilic substances dissolve in water, they are polar molecules that form hydrogen bonds with water.
