Presentation on theme: "Section 2 Water and Solutions"— Presentation transcript:
1 Section 2 Water and Solutions Chapter 2Section 2Water and SolutionsGrade 10 BiologyFall 2010
2 Bell Ringer http://www.youtube.com/watch?v=orW7CEwcAW8 List some common acids and basesWhy do you think water is such an essential compound?
3 Objectives Analyze the properties of water Describe how water dissolves substancesDistinguish between acids and bases
4 Water in Living Things 70 percent of your body is made of water About two-thirds of the molecules in your body are water moleculesWater is the medium in which most cellular events take place
5 Storage of EnergyWater absorbs heat more slowly and retains this energy longer than many other substances doMany organisms release excess heat through water evaporationEx. SweatingIn organisms, the ability to control temp. enables cells to maintain a constant internal temp. when the external temp. changesHomeostasis
6 Cohesion and AdhesionHydrogen bonds between molecules cause the cohesion of liquid waterCohesion: an attraction between substances of the same kindMolecules at the surface of water are linked together by hydrogen bondsThis attraction between water molecules causes a condition known as surface tension
7 Cohesion and AdhesionWater molecules are attracted to similarly polar substancesAdhesion: an attraction between different substancesAdhesion powers process called capillary action
9 Aqueous SolutionsSolution: a mixture in which one or more substances are evenly distributed in another substanceMany important substances in the body have been dissolved in blood or other aqueous fluidsBecause these substances can dissolve in water, they can more easily move within and between cells
10 PolarityThe polarity of water enables many substances to dissolve in waterWater is a polar substance
11 Polarity Ionic compounds and polar molecules dissolve best in water Why?When dissolved in water ions become surrounded by polar water moleculesIons are attracted to the ends of water molecules with the opposite charge, solution is mixture of water molecules and ionsSimilar attraction results with polar moleculesIons or molecules become evenly distributed in water
12 Polarity Non-polar molecules do not dissolve well in water Why?When non-polar substances are placed in water, the water molecules are more attracted to themselves than the non-polar moleculesResult is the non-polar molecules are shoved together
13 Acids Acids: compounds that form hydrogen ions when dissolved in water When an acid is added to water, the concentration of hydrogen ions in the solution is increased above that of pure waterHydrogen ion = H+Acidic compounds have a pH value less than 7
14 BasesBase: compounds that reduce the concentration of hydrogen ions in a solutionMany bases form hydroxide ions when dissolved in waterHydroxide ion = OH-Basic compounds have a pH value greater than 7
15 pH pH scale: based on the concentration of hydrogen ions in solution All solutions have a pH value between 0 and 14Each whole number represents a factor of 10A solution with a pH value of 5, has 10 times as many hydrogen ions as one with a pH value of 6
16 Review T/F Non-polar molecules dissolve very easily in water. T/F Cohesion and adhesion of water molecules help a plant move water from its roots to its leaves.T/F When a base is added to water, the concentration of hydrogen ions increases.T/F A substance has a pH value of 11 therefore it is basic.
17 Answer F: Non-polar molecules dissolve very easily in water. T: Cohesion and adhesion of water molecules help a plant move water from its roots to its leaves.F: When a base is added to water, the concentration of hydrogen ions increases.T: A substance has a pH value of 11 therefore it is basic.