ch3 Flashcards
How to draw hydrogen bonds between water and how do they form?
- regions of neighbouring water molecules with opposite partial charges are attracted to each other causing a h bond to form.
- due to oxygens electron arrangement it is able to have two hydrogen bonds
- these bonds form break and reform rapidly
what are the 4 properties of water due to its H-bonds?
- Cohesive
- moderates temp changes
- versatile solvent
- ice is less dense
explain each property and its biological importance
-cohesive:
hydrogen bonding keeps water molecules together causing high surface tension
aids in water transport up a plant as it helps keep water together in a column in the cells(with the help of adhesion)
when the water evaporates from the leaves, the evaporation pulls water up from the roots.
-moderates temp changes
has high specific heat 1 cal/g
Water can absorb / release a large amount of heat with only a slight change in its own temp
Water resists temperature changes
Water acts like temperature buffer
high heat of evaporation
The high specific heat of water stabilizes ocean temperatures, creating a favorable environment for marine life.
organisms are made primarily of water, they are better able to resist changes in their own temperature
-ice less dense
H-bonds hold molecules ‘arms length’ apart causing large spaces between each molecules making them less dense
water gets the most dense at 4 C as as there are fewer h-bonds so molecules are able to slip close together but above 4 they start expanding again as molecules move faster.
if ice sank then lakes and oceans would freeze destroying the aquatic environment hence ice being able to float provides a stable environment underneath, the solid ice also provides a habitat for animals such as polar bears
-water is a versatile solvent
dissolving agent is a solvent and substance being dissolved is solute
even molecules as large as proteins can dissolve due to ionic and polar bonds
Substances that are non-ionic and non-polar repel water as they are hydrophilic
Working inward from the surface of each salt crystal, water eventually dissolves all the ions. The result is a solution of two solutes
polar compounds and ions are dissolved in biological fluid such as blood and sap of plants
• What is polarity?
having poles or being polar
• describe the polarity of water?
polarity of water creates a slightly positive charge on hydrogen and a slightly negative charge on oxygen due to oxygen being more electronegative then hydrogen
• what is dipoles ? explain why they occur
a pair of equal and opposite electric charges separated especially by a small distance.
occur when two atoms in a molecule have substantially different electronegativity: One atom attracts electrons more than another, becoming more negative, while the other atom becomes more positive
• why is water polar ?
Water is polar because of the V shape of the molecule and unequal sharing of electrons due to oxygen being more electronegative.
what is surface tension?
measure of how hard it is to break the surface of a liquid
• Define kinetic energy
energy that it possesses due to its motion.
• define thermal or heat energy
energy that is generated and measured by heat.
is produced when a rise in temperature causes atoms and molecules to move faster and collide with each other.
• define temperature
it is the average kinetic energy of molecules
• define heat transfer
transfer of heat from hot region to cold region until temperature is the same
• define calorie
amount of heat it requires to raise 1 g of water by 1 C
• define kilocalorie
unit of energy of one thousand calories
joule to cal
1J = 0.239 cal
