1. Opposites Attract Using Chemistry to Explain Biology

2. Atoms ●a - not ●tom - to cut ●a + tom = not cuttable ●Basic units of all matter ●Made up: o Neutron = neutral o Proton = positive o Electron = negative ●Electrons and protons are attracted to each other... ●But electrons move too much to join the protons in the nucleus

3. Atoms ●When... o there are equal numbers of protons and electrons = no charge o there are more protons than electrons = positive charge o there are less protons than electrons = negative charge ●If an atom has a charge, called ion

4. Compounds ●When two or more atoms (elements) bond to each other ●Compounds properties are very different from individual atoms ●Ex) Na + Cl = Salt https://www.youtube.com/watch?v=ODf_sPexS2Q https://www.youtube.com/watch?v=aK85PZX2xNE

5. Compounds ●Created using bonds ●Three types of bonds...

6. Ionic Bonds (The Taker and the Giver) ●Electron is transferred from one atom to the other atom ●One atom adds an electron and gains a negative charge ●One atom loses an electron and gains a positive charge ●Since the atoms are charged, they are ions ●Ex) Salt = NaCl o Na loses electron o Cl gains electron

7. Covalent Bonds (The sharers) ●Neither atom has enough electrons ●Atoms share electrons ●Ex) Carbon dioxide

8. Van der Waals Forces (The Stickers) ●Weakest of three bonds ●Covalent bonds don’t always share equally ●Some atoms attract electrons more than others ●When molecules close together, creates attraction ●“Sticky” ●Ex) Water, H 2 O o Electrons more attracted to oxygen (O) and stay near it more o Oxygen slightly more negative than hydrogen (H)

9. Bonding Activity ●Form groups of four (student choice) ●Pretend you are all atoms trying to become compounds ●Create a simulation for all three types of bonds o Ionic o Covalent o Van der Waals ●When you are ready, come to Ms. Crocker. She will pick a bond for your group to act out

10. Water - The Most Important Compound ● Most abundant Compound in all life ●Many unique properties make it suited to support life o Polarity o Hydrogen Bonds o Solubility o High specific heat capacity

11. Polarity ●Caused by Van der waals forces ●Creates hydrogen bonds in H 2 O o Slightly negative O is attracted to slightly positive H ●Hydrogen bonds create cohesion and adhesion

12. Hydrogen Bonds - Cohesion ●Slight charge of water molecules attract other water molecules http://www.youtube.com/watch?v=45yabrnryXk&t=0m46s

13. Hydrogen Bonds - Adhesion ●Slight charge in water molecules makes it stick to other types of molecules

14. Solubility ●Polarity means it can break apart ionic and polar molecules ●Ex) Salt Water o Negative Cl surrounded by positive H o Positive Na surrounded by negative O ●Nonpolar molecules stay separate o Ex) Oil (nonpolar) and Water (polar) do not mix ●Important for many characteristics of life o Ex) Dissolves solids in our body to be carried in our blood

15. High Specific Heat Capacity ●Water needs a lot of energy to raise by 1 degree o Water is “sticky” due to cohesion, so needs more energy ●Helps to maintain an important characteristic of life - homeostasis ●Homeostasis maintains internal conditions like temperature, nutrient levels, and water content ●High water content means our temperatures don’t change easily

16. Properties of Water Worksheet ●Working individually or in pairs with the person sitting next to you, fill out the worksheet ●We will discuss this in class ●Be prepared to share your answers

17. Acids and Bases ●Water is constantly reacting (breaking apart) to form ions (charged molecules) o H 2 O → H+ & OH- (Ions - Broken apart) o H+ & OH- → H 2 O (Neutral - Reformed) ●In pure water - 1 in 550 million water molecules are ions

18. pH Scale ●Measures H+ ions in a solution ●On a scale from 0 to 14 ●More H+ is lower on the scale ●7 is neutral ●Logarithmic scale (something with a ph of 1 has 10x more H+ atoms than something with a pH of 2)

19. pH Indicators ●Tests the amount of free H+ ions in a solution ●Will change different colors depending on the pH level of a solution ●Ex) Bromothymol Blue o http://www.youtube.com/watch?v=opsNV4VqAbk http://www.youtube.com/watch?v=opsNV4VqAbk

20. Acids ●Chemicals that contain more H+ than pure water ●More H+ than OH- ●pH is below seven ●Strong acids have a pH of 0-2

21. Bases ●Chemicals that contain less H+ than pure water ●Less H+ than OH- ●pH greater than 7 ●Strong bases have a pH of 11-14

22. Turn and Talk ●Why do you think strong acids and strong bases are so corrosive (damaging, can cause burns)?

23. Turn and Talk ●What do you think happens when you mix a strong acid and a strong base?

24. Buffers ●To maintain homeostasis, the body needs to maintain fluids between pH of 6.5 and 7.5 ●Uses buffers o can either be a weak acid or base (close in pH to the neutral of 7) o in presence of strong acid, acts as weak base to accept extra H+ o in presence of strong base, acts as weak acid to accept OH- o reduces rapid pH changes ●Ex) Bicarbonate molecules in blood (HCO 3 - )

25. pH Practice ●In your notes, identify the following as acid or base o Human Blood - 7.4 o Rain - 5.6 o Bleach - 12.6 o Stomach Acid - 1.5 o Battery Acid - 0 o Urine - 6 o Seawater - 8 ●Identify the strongest acid and strongest base ●Identify the weakest acid and weakest base