CH 4:

1. CH 4: The Chemical Basis of Life

2. Concept 4.1 Life Requires about 25 Chemicals

3. 1. Four most abundant elements in your body… • Oxygen (65%) • Carbon (18.5%) • Hydrogen (9.5%) • Nitrogen (3.3%) • Trace elements- in small amounts/ BIG importance • Ex: iodine & iron

4. 2. How are elements & compounds different? • Elements: • Distinct properties (solid, green, density) • All one type of atom • Will be listed on periodic table • Ex: Na, Cl, O, C • Compounds: • Properties different from each of elements • 2 or more types of atoms bonded together • NOT on periodic table • Ex: NaOH, NaCl Element Video Compound Video

5. 3. Examples of trace elements… • Less than .01% • Iron=helps blood carry Oxygen • Iodine=helps thyroid function properly • Usually available through a normal, healthy diet • Who might have problems?

6. 4.1 Vocabulary • Matter • Element • Trace element • Compound

7. Concept Check Questions 4.1 • 1. List the four most abundant elements in your body, in order of decreasing percent of body mass.2. How are elements and compounds different?3. Give an example showing the importance of trace elements to the human body.

8. Concept 4.2 Chemical properties are based on the structure of atoms

9. 1. Subatomic Particles • Protons (p+) • Neutrons (N) • Electrons (e-) • P + N = Nucleus (mass) • e- = electron cloud (no mass)

10. 2. Isotopes & Radioactive Isotopes • Elements with same number of P but different number of N • Same element but with different masses • Radioactive- decay, can be used as “tracers” or “markers”

11. 3. Significance of e- energy levels • Full levels= happy atoms (little reactivity) • Partially full levels= unstable atoms (more reactivity) • Either want to empty levels • Or fill levels • By giving, taking or sharing (bonding) Electrons and Energy Video

12. 4. Atomic Number • Identifies the element (type of atom) • Tells the number of protons in that atom • Makes it distinct • Each element has its own properties

13. 4.2 Vocabulary • Atom • Proton • Electron • Neutron • Nucleus • Atomic number • Isotope • Radioactive isotope

14. Concept Check 4.2 • 1. Describe three kinds of subatomic particles and tell how they are arranged in an atom.2. What is an isotope? Explain how radioactive isotopes are useful to researchers.3. Describe the significance of the number of electrons in an atom's highest energy level.4. Explain the significance of an element's atomic number.

15. Concept 4.3 Chemical bonds join atoms to one another Atoms & Bonding Video Intro to Chemical Bonding Video

16. 1. Ionic Bonds vs. Covalent Bonds • An electron actually moves from one atom to another, will orbit the other’s nucleus • Takes a -1 charge with it Ionic Bonding Video

17. 1. Ionic Bonds vs. Covalent Bonds • Electrons are shared between two atoms • Electron will orbit around both nuclei • Which ever nuclei it orbits around most, is more negative • Creates a polar molecule Covalent Bonding Video

18. 2. & 3. Molecules • Molecules=atoms joined together with covalent bonds • Smallest amount of that compound • Represented with: • Chemical formulas • Structural formulas • Models

19. 4. Number of Bonds (Carbon) • Usually an atoms can bond 1 time for each “empty” electron space in its orbital

20. 4.3 Vocabulary • Ionic bond • Ion • Covalent bond • Molecule • Chemical reaction • Reactant • product

21. Concept Check 4.3 • 1. Describe how an ionic bond forms. How is this process different from the formation of a covalent bond? 2. In a molecule represented by the chemical formula C6H12O6, how many atoms of each element are present?3. What information does a chemical equation provide about a chemical reaction?4. A carbon atom has 4 electrons in its highest energy level. How many hydrogen atoms could become bonded to a single carbon atom?

22. Concept 4.4 Life depends on the unique properties of water

23. 1. Structure of water molecule • 2 Hydrogen atoms covalently bonded to 1 oxygen atom • Polar • A molecule • Displays hydrogen bonding • Weak attraction between a H atom and another slightly negative atom

24. 2. Attraction between water molecules • Cohesion= sticking of similar molecules to each other • Hydrogens of one water molecule are constantly forming hydrogen bonds (and then breaking them) with other water molecules • Cohesion is particularly strong for the compound water

25. 3. Importance of water cohesion • Keeps large molecules organized • Particularly important for water when moving up a plant • Also gives water a high surface tension

26. 4. Ice and Water as a solvent • Thank goodness ice floats… due to the way hydrogen bonds form • Cause a low density • Allows ponds to freeze from top down • Water is the main solvent in most cells, blood and sap • Can dissolve ionic an some covalent bonds

27. 5. pH Scale • Describes how acidic or basic a substance is • Measures amount of H+ ions vs. OH- ions in a substance • Buffers: Donate & absorb H+ • Range: 0-14 • 7=neutral or equal amounts

28. 6. Earth supports life because… • Available liquid water • Viable temperature from the sun • Ozone prevents “frying up”

29. 7. Water moderated temperature • Heat entering water breaks bonds • Once bonds are broken, temperature begins to increase • Prevents rapid and easy increase of temperature • This is why it takes water so long to boil… • Large bodies of water moderate climate • Ex: The “lake effect”

30. Polar molecule Hydrogen bond Cohesion Adhesion Thermal energy Temperature Solution Solvent Solute Aqueous solution Acid Base pH scale buffer 4.4 Vocabulary Water Video

31. Concept Check 4.4 • 1. Explain how the structure of water molecules results in attractions among them.2. Give an example of how cohesion among water molecules is important to living things.3. Describe the information the pH scale provides.4. Name three conditions on Earth that make the planet suitable for life.5. Explain one way in which water can moderate temperature.