Water Properties PDF

SIGNIFICANCE OF WATER Water is a polar molecule It is a covalent compound it shares its electrons unequally between the hydrogen atoms & the oxygen atom. the oxygen atom becomes a little bit negative, the hydrogen atoms becoming a little bit positive Water is a “polar covalent” mo...

SIGNIFICANCE OF WATER Water is a polar molecule It is a covalent compound it shares its electrons unequally between the hydrogen atoms & the oxygen atom. the oxygen atom becomes a little bit negative, the hydrogen atoms becoming a little bit positive Water is a “polar covalent” molecule due to these charged ends. This feature gives water a number of unique properties...  Water is the ‘Universal Solvent’ Water dissolves a large number and variety of solutes, sodium ion both organic & inorganic, chloride ion and both polar & ionic. example: NaCl is an ionic compound When salt crystals are placed in water, the slightly positive and negative ends of the water NaCl in water molecules attract the ions in the crystal. The ionic bonds holding the sodium and chlorine ions together are broken and the ions are pulled into solution.  Water finds itself attractive Water tends to be cohesive, as it forms hydrogen bonds with itself. COHESION = water molecules stick to one another ADHESION = water molecules stick to other surfaces As a result, water molecules stick to one another which allows for: Surface tension – water can support small objects. The hydrogen bonds between neighboring molecules cause a “film” to develop at the surface. Transpiration – This causes water to move upward against gravity in plant stems. It also causes water to adhere to spider webs Circulation – water has the ability to“climb” structures & flow through tubes. Water has a high specific heat capacity The specific heat capacity of water is H 2O = 4200 J / kg’C This means that a lot of energy (4200J of energy) is needed to raise the temperature of 1kg of water by 1 degree Celsius. Conversely, water can lose a lot of energy without a significant drop in temperature. Water acts as an Water acts as a insulator coolant water doesn’t easily change When water evaporates, temperature. energy is used to change This helps living organisms state. maintain a steady internal This lowers the body temperature. temperature via sweating or panting Water acts as a habitat many organisms live in water (lakes, oceans, etc) they depend on the water temperature to regulate their internal temperature. Since water requires a substantial drop in energy to freeze, it remains liquid under the ice cap. Water is involved in chemical reactions Many reactions occur in an aqueous environment & many produce water or use water as a reactant. Hydrolysis: is a chemical process in which compounds are cleaved into two parts by the addition of a molecule of water. One fragment of the original molecule gains a hydrogen ion, H+ from the water the other group collects the remaining hydroxyl group,OH − Condensation: Also called dehydration synthesis Is the reverse of hydrolysis Two molecules combine to form a larger molecule, with the loss of a water molecule Dissociation: Is a process in which molecules or ionic compounds separated into smaller particles. Is usually reversible Is often facilitated when molecules are placed into water Water is a buffer: Buffer = a chemical that resists changes in pH Water can split into H+ and OH- ions In pure (distilled) water, the concentration of H+ and OH- ions is equal this results in a neutral pH - water is neither acidic nor alkaline All organisms are composed mostly of water, which helps them maintain an optimal pH pH impacts the activity of enzymes Water is transparent: It permits sunlight to transmit through it Photosynthesis can occur in aquatic systems Animal can see through water