UNIT 10: Water. Essential Idea(s): Water is the medium of life. IB Assessment Statements

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1 UNIT 10: Water Name: Essential Idea(s): Water is the medium of life. IB Assessment Statements 2.2.U1 2.2.NOS 2.2.U2 2.2.A1 2.2.A2 2.2.U3 2.2.A3 Water molecules are polar and hydrogen bonds form between them. Describe the structure of an atom (in terms of protons, neutrons and electrons). Contrast ion with atom. Define anion and cation. Contrast covalent, ionic and hydrogen bonds. Write the molecular formula for water and draw the atomic structure of the molecule. Describe the cause and effect of the polar nature of water. Describe where and how water is able to form hydrogen bonds. Use of theories to explain natural phenomena- the theory that hydrogen bonds form between water molecules explain the properties of water. List four reasons that suggest the hydrogen bond theory is correct. State why scientists cannot prove without a doubt that hydrogen bonds exist between water molecules. Hydrogen bonding and dipolarity explain the cohesive, adhesive, thermal and solvent properties of water. Contrast adhesion with cohesion. Outline an example of the cohesive property of water being of benefit to life. Outline an example of the adhesive property of water being of benefit to life. Explain three thermal properties of water that are useful to living organisms. Outline a benefit to life of water's high specific heat capacity. Outline a benefit to life of water's high latent heat of vaporization. Outline a benefit to life of water's high boiling point. Explain why is water such a good solvent. List the types of molecules that water will dissolve. Comparison of the thermal properties of water with those of methane. Compare and contrast that chemical and physical properties of methane and water. Explain why water and methane have different thermal properties based on their molecular structures. Use of water as a coolant in sweat. Explain sweating as a mechanism to cool the body. Substances can be hydrophilic or hydrophobic. State that polar and ionic molecules are hydrophilic. State that non-polar, non-ionic molecules are hydrophobic. Given a diagram of a molecular structure, determine if the molecule is hydrophilic or hydrophobic. Modes of transport of glucose, amino acids, cholesterol, fats, oxygen, and sodium in blood in relations to their solubility in water. State if the following molecules are hydrophobic or hydrophilic: glucose, amino acids, cholesterol, fats, oxygen, and sodium chloride. Outline the mechanism of transport in the blood of the following molecules: glucose, amino acids, cholesterol, fats, oxygen, and sodium chloride.

2 Basics of Biochemistry Neutrons: In the atomic nucleus, which provides Protons: Electrons: Electrons interact with Cations: Anions:

3 Polar Covalent bond Non-polar Ionic bond Chemical Bonds: holding molecules together Type Description Example Diagram

4 Type Description Example Diagram Hydrogen bond * *actually an intermolecular force, not a true bond. But, the name is the name.

molecule are attracted to the partially atom of another The bonds are and quickly as the,

5 Water, Water Everywhere Structure of Water Water molecules are polar The e- are The oxygen atom Results in: Water molecules can form hydrogen bonds Partially atoms of one water molecule are attracted to the partially atom of another The bonds are and quickly as the, however the of contribute to the of water. Evidence Supporting Hydrogen Bond Theory Proof Beyond Doubt?

BIOLOGICALLY IMPORTANT PROPERTIES OF WATER Significance Property Explanation for Life ICE FLOATS Ice floats and insulates the underlying water so many plants and animals are not frozen SOLVENT

6 BIOLOGICALLY IMPORTANT PROPERTIES OF WATER Significance Property Explanation for Life ICE FLOATS Ice floats and insulates the underlying water so many plants and animals are not frozen SOLVENT COHESION Water is the main transport medium for dissolved nutrients. In animals, blood (mostly water) goes through out all parts of the body, carrying nutrients. In plants, water carries nutrients up plants and through leaves. Cohesion explains how water molecules can form a chain in delivering moisture to the top of a tree or through the blood stream Cohesion of water molecules along a surface produces SURFACE TENSION ADHESION Adhesion helps water climb up the thin tubes of plants to the leaves Adhesion and cohesion of water allows for CAPILLARY ACTION HIGH SPECIFIC HEAT Contents of cells are unlikely to freeze. Aquatic environments are thermally stable. Organisms have stable internal temperatures when the external temperature is fluctuating. HIGH HEAT OF VAPORIZATION Organisms rely on hear of vaporization to remove body heat to remain cool. Evaporative cooling.

7 SOLUBILITY IN WATER MOLECULE Glucose -PHILIC/- PHOBIC EXPLANATION IMPLICATION Amino Acid Oxygen Cholesterol Fat Sodium Chloride (salt)

8 COMPARING WATER TO METHANE METHANE WATER FORMULA BONDING POLARITY DENSITY IMPLICATIONS HEAT CAPACITY HEAT OF VAPORIZATION MELTING POINT BOILING POINT

REVIEW: Water Structure

REVIEW: Water Structure A water molecule consists of 2 hydrogen and 1 oxygen atom, hence H 2 O. Electrons are shared through polar covalent bonding between the atoms. REVIEW: Water molecules can form hydrogen