2.2 water Flashcards
Hydrogen bond
A weak intermolecular force between two polar molecules. The oxygen in one water molecule hydrogen bonds with the hydrogen of another water molecule
Intermolecular force
An attraction between two molecules
Energy (Joules)
Allows for work (ex: heat and kinetic energy)
Boiling point
The temperature at which liquid becomes a gas (100 degrees C in water)
Melting point
The temperature a solid becomes a liquid (0 degrees C in water)
Specific heat capacity
The amount of energy required to raise the temperature of 1g of a substance by 1 degree Celsius
Latent heat of vaporization
The amount of energy needed to evaporate a substance at its boiling point
Evaporation
Liquid to gas
Solvent
A substance that dissolves another substance
Solubility
Having the ability to dissolve
Cohesion
Attraction between two molecules of the same kind
Adhesion
Attraction between two different molecules or surfaces
Covalent bonds
When they share electrons (ex: oxygen and hydrogen share electrons)
What is electron-greedy? (Electronegative)
When an element has a high affinity for electrons so it tends to pull electrons towards its nucleus (like oxygen)
Is hyrdogen electron-greedy?
No, it only has one proton in its nucleus so it doesn’t hold electrons very well
What symbol represents being negatively or positively charged?
Delta
What is polar molecule called?
A dipole
Up to how many h-bonds can a water molecule form?
4
What can a positively charged hydrogen atom form an h-bond with?
A negatively charged fluorine, oxygen, or nitrogen atom of another molecule
Why does water have high surface tension?
Bc it sticks to itself (it’s cohesive)
Why does water have a high heat capacity?
Bc it takes a lot of energy to break a hydrogen bond and cause the water molecules to start evaporating
What must happen before a change if state can occur?
Hydrogen bonds must be broken
Why is water an excellent medium for living organisms?
It is slow to change temperature and thus supports the maintenance of constant conditions
Water vs Methane
- Water is polar
- can form intermolecular hydrogen bonds
- hydrogen bonds b/w molecules absorb heat energy, reducing kinetic energy
Methane vs water
- methane is non-polar
- can only form weak dispersion forces b/w its molecules
- bc it has no h-bonds, heat creates more kinetic energy
What is the average energy of a hydrogen bond?
20 kJ/mol
Water vs. methane: Which has a higher melting + boiling point?
Water
Water vs. methane: Which has a higher specific heat capacity?
Water
Water vs. methane: Which has a higher heat if vaporization?
Water
Water vs. methane: Which has a higher heat of fusion?
Water
Process of sweating
- When you get hot, the heat excites the water molecules on your skin so much that it breaks the hydrogen bonds
- The sweat evaporates and takes away the heat
How does cohesion allow bugs and the Basilisk lizard to walk on its surface?
The high surface tension of water makes it sufficiently dense for certain smaller organisms to move along its surface
What has the highest cohesion of any non-metallic liquid?
Water
What is the significance of adhesion?
Water can move via capillary action
Capillary action
Attraction to charged or polar substances (e.g. glass) allows water to flow against gravity
How does capillary action relate to plants?
Water is transported up the xylem via transpiration
What can water dissolve?
Any substance that contains charged particles (ions) or electronegative atoms (polar)
Hydrophilic substances
- Substances that dissolve in water
- all polar molecules and ions
How do hydrophilic substances dissolve?
Their polarity is stronger than the cohesive forces of the water, so they break the H-bonds. The water will then form H-bonds around the polar substance
Significance of water’s solvent property
Water is a good transport medium (e.g. the blood system can transport soluble materials in its plasma)
Water soluble substances
- NaCl
- oxygen (in low amounts)
- many hydroxyl groups
- amino acids (in ionized state)
Hydrophobic substances
- large, non-polar substances (such as fats and oils)
- cannot penetrate the strong cohesive forces or water
- do no dissolve
How do lipids travel through the bloodstream?
They form complexes with proteins (making lipoproteins)
Which is more dense: solid or liquid (water)?
Liquid is more dense
Significance of water density
Ice floats on water -> prevents oceans from freezing as ice layer prevents exposure to cold temperatures
Significance of water’s transparency
Aquatic plants can undergo photosynthesis
freezing point
the temperature at which a liquid solidifies (0°C for water).
hydrophilic
molecules capable of interacting with water through hydrogen bonding (having an affinity for water).
hydrophobic
molecules that lack an affinity for water (water insoluble).
methane
a light, colourless gas (CH4).
polarity
property of having distinct and opposite charges (poles).
surface tension (of water)
the intermolecular hydrogen bonds between molecules of water at the surface.
transparency
property that allows light to penetrate molecules of water.
draw a hydrogen molecule
see p. 171
draw a hydrogen bond
see p.171
how does sodium chloride travel in the blood?
ionic compound dissolving in water carried in the blood’s plasma.
how do amino acids travel in the blood?
negative and positive charges. Soluble in water but their solubility depends on the R group, being hydrophilic or hydrophobic. All are carried in the blood plasma.
how does glucose travel in the blood?
polar molecule. Freely soluble in water and is dissolved in blood plasma.
how does oxygen travel in the blood?
nonpolar molecule. Dissolves in water sparingly and can be saturated. Hemoglobin has been developed to bind with
oxygen and increase the capacity of blood to transport oxygen.
blood plasma
the liquid component of blood and is composed of water which contains proteins, ions, and dissolved nutrients.
chemical formula of urea
CO(NH₂)₂
