2.2 Flashcards
What does water consist of
two hydrogen atoms and one oxygen atom joined by covalent bonds
what charge is oxygen
is is more electronegative than hydrogen atoms meaning it has a greater pull on the electron cloud
meaning it has a slightly negative charge, leaving hyrogen atoms with a slightly positive charge
what charge is hydrogen
slightly positive
why does water have such important biological properties
because of its polarity
what is polarity
the property of being polar
why are water molecules polar
due to their dual nature, they have both positive and negative charges and act like small magnets
allowing for the formation of hydrogen bonds between water molecules; the partial positive hydrogen atoms of one molecule are attracted to the partial negative oxygen atoms of other water molecules.
what are hydrogen bonds
weak interactions between water molecules and are responsible for many important properties of water such as cohesion and adhesion
how are hydrogen and covalent bonds depicted
covalent bods - straight bold line
hydrogen bonds - dotted thin lines
what does the polarity of water allow them to do
allows them to attract other polar or charged compounds and form hydrogen bonds with them, meaning the most polar or charged compounds can be dissolves in waters such as sugars and salts
what are good examples of hydrophilic compounds
sugars and salts
what are non-polar substances examples
fats and oils
why do fats and oils not dissolve in water
there is no attraction between them, they repel each other because they are hydrophobic
what else has very strong hydrophobic properties
waxy cuticle on the lead, causing water to form droplets to minims contact between the lead and the water
a hydrophilic substance is one that is
soluble in water
what is cohesion
the tendency of water molecules to stick to each other due to the hydrogen bonding between them
each water molecule can potentially form four hydrogen bonds with other water molecules in a tetrahedral arrangement
what allows for high surface tension of water
the large amount of hydrogen bonds gives cohesive forces great strength, allowing stickiness of water, causing it to act as a strong elastic membrane, allowing small organisms that are denser than water to float on the water surface.
what is surface tension also responsible
for water droplets adopting a spherical shape, minimizing the ratio of area to volume
what is adhesion
this is the interaction that water molecules have with other different molecules (eg glass surfaces) which explains why water molecules stick to other polar compounds by forming hydrogen bonds
what do forces of adhesion result in
capillary action
what is capillary action
the movement of water molecules and all the things that are dissolved in it within thin spaces without relying on gravity
why is adhesion and capillary action important
allows for water to be transported up the stems of plants
what is the difference between cohesion and adhesion
cohesion is interaction among water molecules while adhesion is interacting between water molecules and a surrounding material or surface
what are thermal properties
the hydrogen bonds that hold water molecules together are responsible for the unique thermal properties of water including the high specific heat capacity
what is specific heat capacity
the amount of heat that must be absorbed or released for 1g of a substance to change its temperature by 1 degree celsius
