Today S Objectives s2

Chemistry of Water Inquiry into Life – pg. 24-28 Today’s Objectives: ▸ Describe characteristics of water and its role in biological systems, including: ▸ Describe the role of water as a solvent, temperature regulator, and lubricant ▸ Describe how the polarity of the water molecule results in hydrogen bonding

Chemistry of Water ▸ Why do we care about water chemistry in a Biology course? ▸ 1) The first cells ______in water ▸ 2) All living things are ______water ▸ 3) Due to hydrogen bonding, water molecules cling together which rises the melting and boiling points. Without hydrogen bonding, most water on the Earth would be steam, making life unlikely ▸ These and other unique properties of water make it ______to the existence of life Cell Compounds ▸ In the formation of ______, both organic or inorganic, atoms must bond together to form ______▸ In order to do this, the ______around the various nuclei in the compound must also be stable. ▸ The stability can be achieved through some degree of ______between the atoms Review of Bonding ▸ If the atoms in a compound share their electrons reasonably equally, their association is termed a ______▸ The alternative is a very ______. This is called ______where it seems as though one atom actually ______- ▸ Neutral atoms become ______when they lose electrons and ______when they gain electrons Polar Covalent Bonding ▸ In between these two extremes is what is termed ______▸ Polar covalent molecules have ______▸ A ______is a region with a slight positive or negative charge. A water molecule is an example of this kind of molecule ▸ If the electrons in a covalent bond are not shared equally by the two atoms, then this is a ______▸ Larger atoms have a greater electronegativity than smaller atoms. ______is the ability of an atom to attract electrons. Bonding in Water ▸ In a water molecule, each hydrogen atom shares an ______with the oxygen atom ▸ The oxygen atom is much ______and tends to attract the shared electrons more (higher ______). Therefore, oxygen has a ______charge while the hydrogen's have a ______charge Polarity of Water ▸ Because water molecules have dipoles, water molecules are loosely ______to one another ▸ The negative charge on the ______attracts the positive charge on the ______▸ This produces a weak bond called a ______▸ Each water molecule can form up to ____ hydrogen bonds at a time with its neighbors ▸ Although the hydrogen bond is ______, the vast number of these bonds gives water it’s unique properties Water is a ______▸ Due to it’s polarity, water ______chemical reactions ▸ It ______a great number of substances, which are then called ______▸ Solutes that are ______dissolve much more ______than non-polar solutes ▸ For example, when ______(such as NaCl), are put into water, the______ends of the water molecules are attracted to the sodium ions, and the ______ends are attracted to the chloride ions ▸ This causes the sodium ions and chloride ions to ______, or dissolve, in water ▸ http :// programs.northlandcollege.edu/biology/Biology1111/animations/dissolve.html ▸ Since blood is mainly water, the ability of water to dissolve and transport substances greatly aids in bringing about necessary ______.

Water regulates temperature ▸ Water can help regulate temperature because of its ______(ability to ______without a great change in temperature) ▸ This is due to the many ______that link water molecules together ▸ In hot weather, water warms slowly, and in winter it releases heat slowly ▸ This property helps us regulate body temperature in different temperatures (our body is over ______!) ▸ As a liquid ______, the surface of the liquid that remains behind cools – called ______▸ This occurs because the most ______molecules are the most likely to evaporate, leaving the ______molecules behind ▸ Example: oceans keep surrounding land masses cool in summer, warm in winter ▸ Example: Body systems are mainly water, so bodies tend to keep fairly constant temperature despite changing external conditions Ice is less dense than liquid water ▸ Therefore, ice forms on top of water, ______lower levels. This allows living things to function ______the ice ▸ If ice was more dense than liquid water, it would ______to the bottom and push more water upwards to freeze ▸ If ice sank, all water would eventually ______Water is transparent ▸ Allows light to ______well into water bodies to the ______below Water is cohesive and adhesive ▸ ______means water molecules stick to ______▸ This is evident because water flows freely, yet water molecules don’t separate from each other ▸ Cohesion plays a major role in the transport of water against gravity in plants ▸ ______means that water molecules stick to ______▸ This keeps surfaces moist and lubricated ▸ Diffusion of gases occurs much more efficiently across moist surfaces ▸ Adhesion also assists in the transport of water against gravity in plants as water adheres to the walls of vessels

Water has a high surface tension ▸ ______is a measure of the ______required to stretch or ______of a liquid ▸ Is related to ______▸ Water has a higher surface tension than most other liquids because ______between molecules ______stretching or breaking ▸ Some animals can stand, walk, or run on the surface of the water because of the surface tension Homework: ▸ Read pg. 24-28 – Chemistry/properties of Water ▸ Read pg. 29-30 – Acids, bases, buffers