Water and Life
Hydrogen bond: O- will bond with H+ on a different molecule of H2O
H2O can form up to 4 bonds
Oxygen is a more electronegative atom than Hydrogen, and this allows it to attract H+ atoms from different molecules.
Each O- atom can form two bonds H+ atoms from other molecules and each H+ atom can form one bond with other O- atoms
Cohesion: H-bonding between like molecules
Surface Tension: measure of how difficult it is to break or stretch surface of liquid
Water is very cohesive because of hydrogen bonding between its molecules, and therefore has a high surface tension.
Adhesion: bonding between unlike molecules
Adhesion of H2O to vessel walls counters the pull of gravity
Transpiration: movement of H2O up plants
H2O clings to each other by cohesion; cling to xylem tubes by adhesion
H bonds are responsible for water’s property of transpiration
They allow H2O molecules to hold together through cohesion and thus act against the force of gravity to move from the roots of a plant to the leaves through water conducting vessels.
Capillary action: the movement of water within porous material due to adhesion, cohesion, and surface tension.
Because water molecules are cohesive to one another and adhesive to the vessel walls of the plant, as the water in plants is transpired a void/hole/pore will be created and more water from the roots will be drawn upward into the plant because of attractions to the walls of tubes within the stems.
Heat: total amount of KE in system
Temperature: measure intensity of heat due to average KE of molecules
Water’s high specific heat
Change temp less when absorbs/loses heat
Large bodies of water absorb and store more heat 🡪 warmer coastal areas
Create stable marine/land environment
Humans ~65% H2O 🡪 stable temp, resist temp. change
Evaporative Cooling
Evaporative cooling: when a liquid evaporates and the surface left behind cools.
This happens because the molecules with the greatest KE evaporate and leave behind the molecules with the smallest KE.
This moderates temps in lakes and ponds, and prevents mammals and plants from overheating.
Water has high heat of vaporization
Molecules with greatest KE leave as gas
Stable temp in lakes & ponds
Cool plants
Human sweat
Insulation by ice
Less dense, floating ice insulates liquid H2O below
Life exists under frozen surface (ponds, lakes, oceans)
Ice = solid habitat (polar bears
Solution: liquid, homogeneous mixture of 2+ substances
Solvent: dissolving agent (liquid)
Solute: dissolved substance
Water: versatile solvent
Water is one of the most commonly used solvents
Though it is not a universal solvent, the polarity of water molecules allows for it to dissolve plenty of solutes because of how polar it is.
Substances with ionic/polar regions can usually dissolve in water.
The liquid result of a solvent and solute in a homogenous mixture is a solution.
Hydrogen bond: O- will bond with H+ on a different molecule of H2O
H2O can form up to 4 bonds
Oxygen is a more electronegative atom than Hydrogen, and this allows it to attract H+ atoms from different molecules.
Each O- atom can form two bonds H+ atoms from other molecules and each H+ atom can form one bond with other O- atoms
Cohesion: H-bonding between like molecules
Surface Tension: measure of how difficult it is to break or stretch surface of liquid
Water is very cohesive because of hydrogen bonding between its molecules, and therefore has a high surface tension.
Adhesion: bonding between unlike molecules
Adhesion of H2O to vessel walls counters the pull of gravity
Transpiration: movement of H2O up plants
H2O clings to each other by cohesion; cling to xylem tubes by adhesion
H bonds are responsible for water’s property of transpiration
They allow H2O molecules to hold together through cohesion and thus act against the force of gravity to move from the roots of a plant to the leaves through water conducting vessels.
Capillary action: the movement of water within porous material due to adhesion, cohesion, and surface tension.
Because water molecules are cohesive to one another and adhesive to the vessel walls of the plant, as the water in plants is transpired a void/hole/pore will be created and more water from the roots will be drawn upward into the plant because of attractions to the walls of tubes within the stems.
Heat: total amount of KE in system
Temperature: measure intensity of heat due to average KE of molecules
Water’s high specific heat
Change temp less when absorbs/loses heat
Large bodies of water absorb and store more heat 🡪 warmer coastal areas
Create stable marine/land environment
Humans ~65% H2O 🡪 stable temp, resist temp. change
Evaporative Cooling
Evaporative cooling: when a liquid evaporates and the surface left behind cools.
This happens because the molecules with the greatest KE evaporate and leave behind the molecules with the smallest KE.
This moderates temps in lakes and ponds, and prevents mammals and plants from overheating.
Water has high heat of vaporization
Molecules with greatest KE leave as gas
Stable temp in lakes & ponds
Cool plants
Human sweat
Insulation by ice
Less dense, floating ice insulates liquid H2O below
Life exists under frozen surface (ponds, lakes, oceans)
Ice = solid habitat (polar bears
Solution: liquid, homogeneous mixture of 2+ substances
Solvent: dissolving agent (liquid)
Solute: dissolved substance
Water: versatile solvent
Water is one of the most commonly used solvents
Though it is not a universal solvent, the polarity of water molecules allows for it to dissolve plenty of solutes because of how polar it is.
Substances with ionic/polar regions can usually dissolve in water.
The liquid result of a solvent and solute in a homogenous mixture is a solution.
