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Delve into the significance of water, covering its abundance on Earth, polar nature, properties like cohesion and high specific heat, and role as a universal solvent. Explore how water conducts in cells, moderates temperatures, and even supports life under frozen surfaces. Understand concepts like molarity, pH scale, and buffers, essential for biological systems in maintaining homeostasis.
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Figure 3.1 Water: A Molecule That Supports All of Life • 3/4 of the Earth’s surface • Abundance is the main reason the Earth is habitable
– + Hydrogenbonds H – + H + – – + Figure 3.2 Polar Nature of Water • Oxygen Highly electro negative • Polarity of water molecules Hydrogen bonds between molecules
Properties of Water • Cohesion: Capillary Action • High Specific Heat: Moderation of Temperature • Ice Floats • Universal Solvent
– + Hydrogenbonds H – + H + – – + Figure 3.2 Cohesion • Bonding to neighboring molecules • Due to hydrogen bonding
Water conducting cells 100 µm Figure 3.3 Cohesion • Transpiration pull water up through the microscopic vessels of plants
Figure 3.4 Cohesion • Surface tension
Water moderates air temperature • Absorbs heat from air that is warmer and releasing the stored heat to air that is cooler
Water High Specific Heat • Amount of heat absorbed or lost to change its temperature • hydrogen bonds • Evaporative Cooling: Sweat
Hydrogen bond Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Figure 3.5 Ice Floats • Hydrogen bonds in ice • More “ordered” than in liquid water less dense
Ice Floats Water is most dense at 4 deg. C • Because ice floats in water life can exist under the frozen surfaces of lakes and polar seas 1.0g/cm3= liquid 0.9g/cm3= ice
Negative oxygen regions of polar water molecules are attracted to sodium cations (Na+). – Na+ + + – + – – Positive hydrogen regions of water molecules cling to chloride anions (Cl–). Na+ – + + Cl – Cl– + – – + – + – – Figure 3.6 Solvent of Life • Polar regions of water molecule interact with ionic compounds
Water: Solvent of Life • Hydophilic • Hydrophobic Benzene
Solute Concentration • Molecular Mass: Sum of the masses of all the atom in a molecule • Avogadro's Numbe: 6.0 x 10-23 Daltons= 1g • Molar Mass: molecular mass x Avogadro’s # (usually on chemical label) (moles) • Molarity : The number of moles of solute per litter of solution.
Examples • If you have 5 M of a solute in 2.5 L of solution what is the molarity of the solution? • The Concentration of a solute in blood is 1.3 x10-10 M. How many molecules of this solute would be in a liter of blood?
What is pH? Hydronium concentration in water is 10-7. pH is –log of H+ concentration Acids increase H+ concentration Bases reduce H+ concentration Acidic = Higher H+ Basic = Higher OH-
pH Scale 0 1 Battery acid 2 Digestive (stomach) juice, lemon juice 3 Vinegar, beer, wine, cola Increasingly Acidic [H+] > [OH–] 4 Tomato juice 5 Black coffee Rainwater 6 Urine Neutral [H+] = [OH–] 7 Pure water Human blood 8 Seawater 9 10 Milk of magnesia Increasingly Basic [H+] < [OH–] 11 Household ammonia 12 Household bleach 13 Oven cleaner 14 Figure 3.8 pH scale
Buffers • Minimize changes in pH • Carbonic acid in the blood
A fat molecule Chapter 4: Carbon Compounds http://www.youtube.com/watch?v=V3NCeSlYQWQ&feature=player_detailpage
