2 Driving QuestionsHow do the special properties of water contribute to Earth’s suitability as an environment of life?How does the arrangement of covalent bonds within a water molecule lead to its polar property
3 Water and SolutionsI want you to compare your body to the body of a jellyfish Do we have anything in common? We may seem different than each other, but we both had bodies that are made of cells that consist mostly of water. The chemical reactions of all living things take place in the aqueous environment of the cell.
4 PolarityIn water molecules, H20, the hydrogen and oxygen atoms share electrons to form Covalent bonds The electrons are not shared equally. Oxygen LOVES electrons! This will cause a partially negative charge on the oxygen This means the hydrogen ends will have a partially positive charge This opposite ended charges cause what why we call water a polar molecule Think “poles”
6 Solubility of WaterThe polar nature of water allows it to dissolve polar substances such as sugars, ionic compounds, and some proteins. Water is an important solvent and helps break down other compounds to smaller more manageable ones.
7 Hydrogen BondingThe polar nature of water causes water molecules to be attracted to one another Positively charged portions of water molecules are attracted to negatively charged portions of another water molecule. Hydrogen bond is the force of attraction between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial or full negative charge
8 Hydrogen BondingThe number of hydrogen bonds that exist depend on the state the water is in. Gas, liquid, solid. Which has more hydrogen bonds? Solid-All water molecules are hydrogen bonded Liquid-more hydrogen bonds are broken than formed Gas-Very little hydrogen bonding occurring It is hydrogen bonding that accounts for our next topic Adhesion and cohesion
9 CohesionWater molecules stick to each other as a result of hydrogen bonding. An attractive force that holds molecules of a single substance together is known as cohesion Cohesion is responsible for surface tension Think of a needle floating on the surface of water. Think of filling water past the rim of a glass, bulges up, doesn’t over flow
10 AdhesionAdhesion is the attractive force between two particles of different substances, such as water molecules and glass molecules Have you ever heard of capillary action? this is the attraction between molecules that results in the rise of the surface of a liquid when in contact with a solid.
11 Temperature moderator Water has high heat capacity. means that water can absorb or release relatively large amounts of energy in the for of heat, with only a slight change in temperature. Did you know the temperature increase of water is due to the breaking of hydrogen bonds? This bond breaking causes the water molecules to move around more releasing energy. If the temperature of water drops, the hydrogen bonds are reformed and energy is not expelled.
12 Density of IceEver wonder why ice floats? It all has to do with hydrogen bonding! Imagine that…. When water freezes, water molecules arrange in a pattern that causes large open spaces. This means there are less molecules of water
13 SolutionsA solution is a mixture in which one of more substances are uniformly distributed in another substance. can be a mixture of liquids, solids, gases A solute is a substance dissolved in a solvent A solvent is the substance in which the solute is dissolved Whenever we use water as the solvent, we call that an aqueous solution These are universally important to life on Earth. There are 3 very important aqueous solutions found in biology