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Unit 1 the role of water

Unit 1 the role of water



This is a detailed powerpoint presentation of the role and functioning of water.

This is a detailed powerpoint presentation of the role and functioning of water.



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    Unit 1 the role of water Unit 1 the role of water Presentation Transcript

    • Clitheroe, F & Dilley, L.(2010),Natural SciencesLearner’s Book, Grade 9.Oxford University Press.ISBN: 9780195762945
    •  Water is a chemical substance withthe chemical formula H2O. Its molecule contains one oxygen and twohydrogen atoms connected bycovalent bonds. Water molecules areconnected by Hydrogenbonds.
    • The polarity of water moleculesresults in hydrogen bonding• Water = unique properties that allows it to support& maintain living systems• – Due to its structure & interaction with othermolecules• The water molecule is a polar molecule: Theopposite ends have opposite charges Polarity allows water molecules to formhydrogen bonds with each otherCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
    • Fig. 3-2Hydrogenbond–H+HO+++–––Slightly + H of 1 moleculeattracted to slightly – O ofnearby molecule –Hydrogen bond keepsthem together.In liq water the bond is veryweak -Continually reforming &breaking
    • Four properties of water contributeto Earth’s fitness for life• 4 of water’s properties that facilitate anenvironment for life are: 1. Cohesive behavior (predictable behavior) 2. Ability to moderate temperature 3. Expansion upon freezing 4. Versatility as a solvent (dissolve varioussubstances)Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
    • ¾ of the Earth’s surface iscovered by water of theoceans.Every cell consists of 50 –90% water.Needed to transportmolecules in & out cells.Many organisms live in water.
    • Water can be found in 3 phases:1. Gasses2. Liquids3. Solids
    •  Consist of water molecules that move aroundfreely: A lot of energy and space between molecules. Attraction between molecules very weak. Called water vapour. Found in atmosphere.
    •  When temperature increases, it causes liquidwater to change to water vapour(evaporate).
    •  Water molecules move around lessthan gasses but more than solids. More energy than solids but lessthan gas. Attraction forces betweenmolecules is stronger than gasmolecules but weaker than solids. It takes on the shape of thecontainer it is in. Found everywhere. If solid water is heated, liquid waterforms.
    •  Solid water molecules are called ice. Molecules only vibrate at one spot.Minimal amount of energy but verystrong attraction forces betweenmolecules. Molecules arrange in a structured waycalled a crystal lattice. Found everywhere. If liquid water is cooled down itbecomes a solid.
    •  Water has a high heat capacity Amount of heat required to raise the temperature of 1g ofwater by 1˚C. Prevents water from freezing or boiling if atmospherictemperature changes protecting aquatic organisms. Water has a high heat of evaporation Amount of heat required to vaporize a liquid. Helps animals, they sweat, water evaporates when theyoverheat, to cool them down. Water has a high heat of fusion Amount of heat required to melt a solid.
    •  More things can dissolve in water than anyother liquid. The liquid that a substance dissolves in iscalled a solvent. Blood contains 55% water called bloodplasma. Gasses have to dissolve in the blood plasmaand then diffuse into the red blood cells totransport the oxygen to the body cells andand carbon dioxide to the lungs.
    •  All chemical reactions to controlmetabolism take place in water. E.g.Digestion, breathing etc. Water takes part in some chemicalreactions e.g. Photosynthesis What is photosynthesis? The processwhereby plants use water, sunlight andcarbon dioxide to produce food andoxygen. Enzymes speed up chemical reactionsin the presence of water.
    •  Water helps transport substances in thebody of a plant or animal: E.g. In humans, food and gasses aretransported via the blood circulatorysystem (consisting of mainly water). E.g. In plants, mineral salts, absorbedfrom the soil are dissolved in water andcarried to all parts of the plant.
    •  Most organisms need water toreproduce. Mosses and ferns can onlyreproduce if they are covered witha thin film of water. All animals need water toreproduce, the sperm needs waterto swim to the ova (egg cell). Aquatic animals reproduce in thewater.
    •  Vertebrates (like humans)have a bonyskeleton to support the shape of theirbodies. Invertebrates do not consist of bones,most of them have water that helps tosupport the body shape, called ahydrostatic skeleton. Water pushes against the sides of the body,exerting pressure to maintain the shape. E.g.Worms and snails. Xylem tubes together with water helpsplants stay upright. (Think about a plant deprived of water)
    •  Humans use “water” to cool down. This water is known as sweat.(perspiring) Sweat is produced by sweat glands. When the sweat evaporates from thebody, it cools down. This happens during strenuous exercise,stress and illness.
    •  Plants lose water through theirleaves. Process of transpiration. Transpiration helps to cool theplant down. What is transpiration? Loss ofwater in the form of watervapour through openings calledstomata, on the leaves ofplants. Helps plants suck water up stemto leavesSTOMATACross section through leaf to see
    •  Cover pot plant/branch of plantwith a plastic bag Seal bag with a string. Leave bag for few hours. Observe Result: Water droplets form onthe sides of the plastic bag. What happened? Transpirationoccurred You can try this at home