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Published byMaximillian Charles Modified over 9 years ago
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Opposites Attract Using Chemistry to Explain Biology
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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
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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
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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
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Compounds ●Created using bonds ●Three types of bonds...
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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
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Covalent Bonds (The sharers) ●Neither atom has enough electrons ●Atoms share electrons ●Ex) Carbon dioxide
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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)
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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
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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
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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
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Hydrogen Bonds - Cohesion ●Slight charge of water molecules attract other water molecules http://www.youtube.com/watch?v=45yabrnryXk&t=0m46s
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Hydrogen Bonds - Adhesion ●Slight charge in water molecules makes it stick to other types of molecules
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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
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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
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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
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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
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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)
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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
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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
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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
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Turn and Talk ●Why do you think strong acids and strong bases are so corrosive (damaging, can cause burns)?
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Turn and Talk ●What do you think happens when you mix a strong acid and a strong base?
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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 - )
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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
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