The Extraordinary Properties of Water

Water A water molecule (H2O), is made up of three atoms --- one oxygen and two hydrogen. H O 1

Water is Polar In each water molecule, the oxygen atom attracts more than its "fair share" of electrons The oxygen end “acts” negative The hydrogen end “acts” positive Causes the water to be POLAR However, Water is neutral (equal number of e- and p+) --- Zero Net Charge

Hydrogen Bonds Exist Between Water Molecules Formed between a highly Electronegative atom of a polar molecule and a Hydrogen One hydrogen bond is weak , but many hydrogen bonds are strong

Interaction Between Water Molecules Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

What are the Properties of Water? 1

Quick Water Facts At sea level, pure water boils at 100 °C and freezes at 0 °C. The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). For this reason, an egg will take longer to boil at higher altitudes 1

Check Your Understanding August Alsina (A2), Mt. McKinley and Poconos Mt. McKinley: 20,322 ft Poconos: 2,693 ft In which place will A2 have to wait longer for his eggs to boil?

Properties of Water Cohesion Adhesion High Specific Heat High Heat of Vaporization Less Dense as a Solid 1

Cohesion Attraction between particles of the same substance ( why water is attracted to itself) Results in Surface tension (a measure of the strength of water’s surface) Produces a surface film on water that allows insects to walk on the surface of water 1

Helps insects walk across water Cohesion … Helps insects walk across water

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Adhesion Attraction between two different substances. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton. Capillary action- adhesion + cohesion; how water travels up thin tube Example: transpiration process which plants and trees remove water from the soil, and paper towels soak up water. 1

Adhesion Causes Capillary Action Which gives water the ability to “climb” structures

High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change, both for heating and cooling. Water can absorb or release large amounts of heat energy with little change in actual temperature. 1

High Heat of Vaporization Amount of energy to convert 1g of a substance from a liquid to a gas In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it. 1

High Heat of Vaporization Water's heat of vaporization is 540 cal/g. In order for water to evaporate, each gram must GAIN 540 calories (temperature doesn’t change --- 100oC). As water evaporates, it removes a lot of heat with it (cooling effect). 1

Water is Less Dense as a Solid Ice is less dense as a solid than as a liquid (ice floats) Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances. 1

Water is Less Dense as a Solid Which is ice and which is water? 1

Water is Less Dense as a Solid Ice 1

Homeostasis Ability to maintain a steady state despite changing conditions Water is important to this process because: a. Makes a good insulator b. Resists temperature change c. Universal solvent d. Coolant e. Ice protects against temperature extremes (insulates frozen lakes) 4

Check Your Understanding In this property of water, water molecules stick to each other very well

Check Your Understanding In this property of water, water molecules stick to each other very well Answer: COHESION

Check Your Understanding In this property of water, capillary action helps transport water up the roots of plants and trees

Check Your Understanding In this property of water, capillary action helps transport water up the roots of plants and trees Answer: ADHESION + COHESION

Check Your Understanding In this property of water, ice floats

Check Your Understanding In this property of water, ice floats ANSWER: Water is less dense as a solid (ice)

Check Your Understanding In this property of water, it takes water a long time to heat up or cool down

Check Your Understanding In this property of water, it takes water a long time to heat up or cool down ANSWER: High specific heat

Check Your Understanding In this property of water, hydrogen bonds are broken down, and 1 g of water requires 540 calories of heat to turn from a liquid to a gas ANSWER: High heat of vaporization

Carbon

Introduction to Carbon Carbon is the basic building block for all forms of life on Earth. Fortunately, carbon is also one of the most abundant elements on our planet. It is the fourth most abundant element in the universe and it is the second most abundant element in the human body. Oxygen is the most abundant element in the human body. Like all matter, carbon can neither be created nor destroyed, and so all living organisms must find a way to continually reuse the finite carbon supply that is available.

Why study Carbon? All of life is built on carbon Cells ~72% H2O ~25% carbon compounds carbohydrates lipids proteins nucleic acids ~3% salts Na, Cl, K… Why do we study carbon -- is it the most abundant element in living organisms? H & O most abundant C is the next most abundant

Chemistry of Life Organic chemistry is the study of carbon compounds C atoms are versatile building blocks bonding properties 4 stable covalent bonds Carbon chemistry = organic chemistry Why is it a foundational atom? What makes it so important? Can’t be a good building block if you only form 1 or 2 bonds. H C H H H

Carbon and Macromolecules! Important thing about carbon is that it can bond with many other elements to form SUPER LONG CHAINS of molecules called MACROMOLECULES!

Macromolecules Smaller organic molecules join together to form larger molecules macromolecules 4 major classes of macromolecules: carbohydrates lipids proteins nucleic acids

Polymers Long molecules built by linking repeating building blocks in a chain monomers building blocks repeated small units covalent bonds H2O HO H • great variety of polymers can be built from a small set of monomers • monomers can be connected in many combinations like the 26 letters in the alphabet can be used to create a great diversity of words • each cell has millions of different macromolecules Dehydration synthesis

How to build a polymer Synthesis joins monomers by “taking” H2O out one monomer donates OH– other monomer donates H+ together these form H2O requires energy & enzymes H2O HO H enzyme Dehydration synthesis Condensation reaction

How to break down a polymer Digestion use H2O to breakdown polymers reverse of dehydration synthesis cleave off one monomer at a time H2O is split into H+ and OH– H+ & OH– attach to ends requires enzymes releases energy H2O HO H enzyme Most macromolecules are polymers • build: condensation (dehydration) reaction • breakdown: hydrolysis An immense variety of polymers can be built from a small set of monomers Hydrolysis Digestion

Check your understanding Why is carbon so essential to life?

Check your understanding Why is carbon so essential to life? ANSWER: Because it is the basic building block of life

Check your understanding What property of carbon allows it to form macromolecules?

Check your understanding What is property of carbon allows it to form macromolecules? ANSWER: It forms four stable covalent bonds

Check your understanding This term refers to long molecules made of up of monomers

Check your understanding This term refers to long molecules made of up of monomers ANSWER: Polymers

Check your understanding Process by which a polymer is formed from monomers

Check your understanding Process by which a polymer is formed from monomers ANSWER: Dehydration synthesis a.k.a. condensation reaction

Check your understanding Process by which a polymer is split up into monomers

Check your understanding Process by which a polymer is split up into monomers ANSWER: Hydrolysis aka Digestion