BIOL1201 Water (1).pdf

Water Structure, Properties and Functions Definition ● Water is made up of tiny molecules of hydrogen and oxygen ○ Two hydrogen and one oxygen ● Pure water is colorless, tasteless and odorless ● Water exist in three forms on Earth ○ ○ ○ Solid (ice, hail, snow, frost) Liquid (rain, oceans, dew, f...

Water Structure, Properties and Functions Definition ● Water is made up of tiny molecules of hydrogen and oxygen ○ Two hydrogen and one oxygen ● Pure water is colorless, tasteless and odorless ● Water exist in three forms on Earth ○ ○ ○ Solid (ice, hail, snow, frost) Liquid (rain, oceans, dew, fog) Gas (steam or water vapor) Background Information ● Water covers two-thirds of the Earth’s surface. ● It is essential for life. Every living thing depends on water. ● The human body is comprised of over 70% of water. ● The structure of water is what allows it to have its properties and makes it essential for life. Covalent bonding ● Consists of 1 oxygen and 2 hydrogen molecules ● The 2 hydrogens are bonded to the oxygen molecule ● Covalently bonded ○ sharing of electrons between oxygen and the hydrogens Bonding and Geometry ● Oxygen and hydrogens attract the shared electrons unequally due to difference in electronegativity so each end of the molecule adopts a slight different charge ○ ○ Partial positive for hydrogen Partial negative charge for oxygen ● Bonds are polar covalent ● The molecule adopts a bent structure because of the two lone pairs of electrons on the oxygen atom. ○ 105 degrees Polarity and Hydrogen Bonds ● Polar molecules are attracted to one another by dipole-dipole forces. ● In the case of water, each hydrogen atom is strongly attracted to the lone-pair electrons on an adjacent oxygen atom. ● These are called hydrogen bonds and are stronger than conventional dipole-dipole forces. Universal Solvent ● ● ● ● ● ● Water is referred to as the universal solvent because of its ability to dissolve more substance than any other liquid. The polarity of water allows it to dissolve and dissociate many particles. It dissolves polar substances (hydrophilic). Non-polar substances do not dissolve in water (hydrophobic). Helps cells transport and use substances like oxygen and nutrients Allow chemical reactions to occur Density ● The density of a substance is its mass per unit volume. ○ ● ● ● It is denoted by the symbol “ρ”. Measures the compactness of a substance. Water is less dense as a solid. Solid – water molecules are bonded together – space between fixed ● Liquid – water molecules are constantly bonding and rebonding – space is always changing Cohesion, Adhesion and Surface Tension Cohesion = water attracted to other water molecules because of polar properties Adhesion = water attracted to other materials Surface tension = water is pulled together creating the smallest surface area possible Capillary Action ● Capillary Action = water’s adhesive property is the cause of capillary action. ● Water is attracted to some other material and then through cohesion, other water molecules move too as a result of the original adhesion. High Heat Capacity ● The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. ● Water has high heat capacity. ○ It takes a lot of energy to raise the temperature of a certain amount of water by a degree ● This property allows water to help regulate the temperature in the environment and in the bodies of living organisms. High Heat of Vaporization ● Heat of Vaporization is the amount of energy needed to change one gram of a liquid substance to a gas at constant temperature. ● Water has a high heat of vaporization. ○ a high input of energy is required to transform one gram of liquid water into water vapor ● Hydrogen bonds makes it difficult to separate the water molecules from each other (high boiling point). ● At boiling point of 100° Celsius , heat is able to break the hydrogen bonds between water molecules and the kinetic energy allows them to escape (vaporize). ● As water evaporates, energy is taken up by the process which then cools the environment. ● This allows humans and other organisms that sweat to maintain homeostasis of body temperature due to evaporative cooling. Acid and Base properties ● Water is referred to as amphiprotic. ○ ○ It can either accept or donate a proton. Thus, it can act as an acid or base. ○ For eg, protein structure can be disrupted by very acidic or basic pH’s. ● Water can buffer cells from the effects of dangerous acids and bases. ● Highly acidic/ basic substances take up excess hydrogens or donate excess hydrogens which can disrupt the structure of molecules in the cells. ● Water protects by acting as either an acid or base by either donating or accepting hydrogens. ● Therefore, it acts as a buffer.