Bellwork: 10/1 Put phone up  Week 10/1-10/5 Turn in chemical bonding worksheet List some properties of water that you already know. Did you have a good weekend?

Objective Students will learn about how biochemistry is an important branch of biology Determine what chemical properties of water make it unique to life Determine what key properties of water makes it biologically significant

Today: Tests back Properties of Water Notes

This Week: Monday: H2O Notes Tuesday: Lab Notebook, Pre-Lab, Water POGIL Wednesday: H2O Lab Thursday: H2O Lab, pH Notes Friday: Internet Safety pt. I & II

Materials Unit 2 Book

Homework Google Classroom Quiz Read pages 4—43 & answer ?s on GC Due Monday @ 11:59pm Read pages 4—43 & answer ?s on GC Due @ 11:59pm tonight

Unit 2: Biochemistry

Part III: Properties of Water

Water Molecules are Polar Why? Oxygen loves electrons Oxygen attracts Hydrogen’s Electrons Makes Oxygen partially negative Makes Hydrogen partially positive Are these bonds covalent or Ionic? Why?

Chemical Bonds Covalent bonds-within water molecule Hydrogen bonds-between water molecules Covalent Bond Hydrogen Bond

Activity On your note guide, draw three water molecules. Indicate the Hydrogen bonds associated with these water molecules with dotted lines. Be ready to share 

Unique Properties Water has unique properties because… It is polar Forms Hydrogen bonds

The Five Properties of Water

1) Excellent Solvent Solvent – dissolving agent of a solution Solute – substance dissolved in the solvent Hydrophilic (polar) – likes water, dissolves Ex. Salt, table sugar Hydrophobic (non-polar) – dislikes water, doesn’t dissolve Ex. oil Solution = solvent (liquid) + solute (may be solid, liq or gas)

Water as a Solvent Water dissolves solutes (ex. table salt, sugar) by forming a hydration shell around the solute

Biological Significance Allows solutes to be dissolved in our blood and transported throughout our body Blood is 90% water

Is ice more or less dense than liquid water?

2) Ice Floats Ice is less dense than liquid water Density= # molecules per volume Fewer molecules per volume in ice...floats! Arsenic, bismuth, galium, germanium, silicon all have more dense liquids

When Water Turns to Ice… A crystal lattice forms Hydrogen bonds hold the water molecules in place Molecules in ice are farther apart than in water Fewer molecules per volume = less dense

Biological Significance Only the surface of lakes and rivers freeze Keeps the water below warmer Stays liquid water Prevents aquatic organisms from freezing

3) Moderates Temperature Water has a high specific heat because of hydrogen bonds. Specific heat is the amount of heat absorbed or released by one gram of substance that causes the temperature to change by 1oC Liquid  gas = absorbs heat because breaking hydrogen bonds Liquid  solid = release heat because forms hydrogen bonds Highest specific heat of any liquid – 1 calorie…H bonds are strong and hard to break Takes water 5 times longer than sand to cool or heat

3) Moderates Temperature Water can absorb heat without changing temperature because of hydrogen bonds. Heat is used to break the hydrogen bonds rather than raising temperature Heat used to break hydrogen bonds when Ice melts to liquid water Liquid water changes to water vapor (a gas) Because of how strong those hydrogen bonds are

Biological Significance Earth has more moderate temperatures because of the lakes, rivers and oceans Favorable temperatures for survival of living organisms

Biological Significance Homeostasis of body temperature Evaporative cooling (sweating) sweat absorbs heat from your body causing the sweat to evaporate You feel cool and don’t overheat

4) Cohesion Attraction between water molecules because of water bonding Causes water to form droplets

Biological Significance Creates strong Surface Tension Insects can walk on water without sinking

5) Adhesion Attraction to unlike substances – like cellulose in the paper straw

Biological Significance Capillary Action Pulls water up a tube Contributes to movement of water up tall trees

Answer the ?s in your Note Guide Properties of Water Questions Explain why water is polar. How does its polarity contribute to its ability to form hydrogen bonds? Describe the five properties of water and explain their biological significance.