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Chemistry of Life

Explore the basic concepts of chemistry in biology, including the composition of matter, the structure of atoms, and the formation of compounds through bonding.

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Chemistry of Life

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  1. Chemistry of Life Chapter 2

  2. Why Learn Chemistry in Biology? • Matter: anything that has mass and takes up space • EVERYTHING is matter; water, air, living things, etc • Matter is NOT light, sound, or energy • ALL matter is made of atoms (living things too!) • An atom is the smallest unit of matter that cannot be broken down by chemical means. • An element is a substance made of only one kind of atom, and it is therefore a pure substance. • All elements are found on the Periodic Table • EVERYTHING IN THE WORLD can be broken down into the elements on the table

  3. Parts of an Atom • All atoms have 3 parts • Proton: P+, positive (+) charge, found in the nucleus • Neutron: N, neutral (0) charge (no charge), found in the nucleus • Electron: e-, negative (-) charge, found in the electron cloud around the nucleus • Atoms are NEUTRAL. Protons (+) are attracted to the electrons (-). • Atoms have the same number of protons and electrons

  4. Atoms and Elements • Elements are made of only 1 kind of atom • Example: oxygen is an element made of only oxygen atoms • Each element has a specific number of protons, neutrons, and electrons • Example: oxygen has 8 p+, 8 n, and 8 e-

  5. Changes in p+, n, and e- • *IF YOU CHANGE THE NUMBER OF PROTONS IN AN ELEMENT, YOU GET A NEW ELEMENT!!!!! • Isotope: atoms that contain different numbers of neutrons • Carbon has 6 protons, 6 neutrons, and 6 electrons • Carbon can have isotopes with different numbers of neutrons, C-12, C-13, C-14 • *all still have 6 protons!!!! • Ion: atoms that have different numbers of electrons • Have an overall electrical charge • Negative if it has extra electrons • Positive if it is missing electrons • *still has the same number of protons!

  6. ATOMIC STRUCTURE He 2 Atomic number the number of protons in an atom and the number of electrons For Helium: p=2, e=2 4 Mass Number the number of protons and neutrons in an atom p + n = mass number Or mass – p = neutrons number of protons = number of electrons

  7. Counting p+, n, and e- • To find the number of protons: • Look at the atomic number • To find the number of electrons: • Same as proton number • To find the number of neutrons: • Subtract protons from mass • Mass – p = neutrons

  8. Bonding • Atoms can combine (bond) together to form compounds and molecules • Compound: a substance made of joined atoms, can be the same element or different ones • Example: H2O (water), NaCl (salt) • Molecule – a group of atoms held together by covalent bonds

  9. Covalent Bond • Covalent Bond: atoms bond together and SHARE electrons • Molecule has no charge • Water (H2O) is formed when oxygen makes a covalent bond and shares electrons with 2 hydrogen atoms

  10. Ionic Bond • Ionic Bond: forms when 2 or more atoms gain or lose electrons and combine electrically • Ex: sodium (Na) is positive, chlorine (Cl) is negative. They form an ionic bond because the Na+ is attracted to the Cl-

  11. Hydrogen Bond • Hydrogen Bond: a weak bond formed between the hydrogen atoms in a compound • Water and DNA have hydrogen bonds

  12. Chemical Reactions (rxns) Molecules become rearranged into other molecules Bonds are broken and new ones form May release or absorb energy Reactants = starting materials (on left of rxn) Products = ending materials (on right of rxn) Same # of each type of atom must be present on each side Example: NaOH + HCl  NaCl + H2O

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  14. Bohr Models • Bohr Model – a drawing of an atom with the correct number of protons, neutrons, and electrons 1. Find the atomic number. Write that in the middle with a “p” next to it. Circle it. This is your number of protons 2. Find the mass number. Subtract the number of protons from the mass number. This is your number of neutrons. Write that next to the proton number with an “n” next to it. Circle it. 3. Protons and neutrons are found in the nucleus. You’ve just made that!

  15. Bohr Models (continued) 4. Electrons are found in “shells” in a cloud around the nucleus (called the “electron cloud” Find the atomic number. This is your number of electrons 5. Shells have specific numbers of electrons that can fit 1st shell = 2 2nd shell = 8 3rd shell = 8 4th or more shells = 18

  16. Bohr Model With Bohr Model diagrams, elements and compounds are represented by dots to show electrons, and circles to show the shells. For example; X Nitrogen N X X 7p+ 7n⁰ X X X X

  17. Why is water so important? • 70% of your body is made of water • Almost 70% of the earth is covered with water • Cells are filled with water, surrounded by water, and need you to drink water to stay healthy • Water is made of 2 hydrogen atoms covalently bonded to 1 oxygen atom (H2O)

  18. Properties of water • Water stores heat • A pot of boiling water takes a long time to cool down to room temperature • A warm ocean or lake will take a long time (many months to freeze) • Water is released from your body as sweat to help you cool down when you are hot (*homeostasis*)

  19. Properties of water • Water bonds to itself and other substances • Cohesion: water can bond to itself • Reason you can “overfill” a glass of water and it not spill • Adhesion: water can bond to other things • Reason that dew and condensation on glasses can leave drips still attached to the surface and not fall off

  20. Properties of WATER COHESION ADHESION

  21. WATER MOLECULE (POLAR MOLECULE) Polarity: substances that are neutral can have ends, or “poles” that are slightly positive and slightly negative Water is Polar – the oxygen is slightly negative and the hydrogens are slightly positive *reason for “hydrogen bonding”*

  22. Properties of WATER Water is the SOLVENT of Life! Solute– substance that is dissolved Solvent– substance that does the dissolving Solution–a mixture in which 1 or more substances are evenly distributed in another substance

  23. Acids • Definition: a compound that donates H+ ions to a solution • EXAMPLE: HCl • In a solution, HCl breaks apart into H+ and Cl- ions

  24. Bases • Definition: a compound that removes H+ ions from a solution • EXAMPLE: NaOH • In a solution, NaOH breaks apart into Na+ and OH- ions

  25. The pH Scale • Definition: describes how acidic or basic a solution is • Ranges from zero (most acidic) to 14 (most basic) • The numbers 0-14 represent a 10-fold change • Example: lemon juice pH = 2 • Grapefruit juice pH = 3 • Lemon juice has 10 times more H+ ions than grapefruit juice

  26. pH • Acid pH = 0-6 • Acids have more H+ ions • Strong acid (SA) = 0-3 • Weak acid (WA) = 4-6 • Neutral = 7 • Neutral solutions have equal H+ and OH- • Base pH = 8-14 • Bases have more OH- ions • Strong base (SB) = 11-14 • Weak base (WB) = 8-10

  27. Buffers • Definition: substances that cause a solution to resist a change in pH • Works by accepting H+ ions when their levels rise (by adding acid) or donating H+ ions when the levels drop (by adding base) • Buffers work to maintain a neutral pH (7) • Your blood is a buffer – you can eat lots of foods with acids or bases and still keep neutral!

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