Daily Practice 10/13/09

1. Daily Practice 10/13/09 • What could you do different this quarter to improve your grade vs. 1st quarter? • What should you do if you miss an assignment? How many days do you have to complete it? • Who’s responsibility is it to make up tests/quiz/assignments? • Turn in any makeup/late work into the tray before the bell rings!!!!!!!!!!!!!!!!!

2. Ch. 2 The Chemistry of Life

3. Section 6.1 Atoms, Elements, and Compounds Objectives Identify the particles that make up atoms. Diagram the particles that make up an atom. Compare covalent bonds and ionic bonds. Describe van der Waals forces.

4. Nature of Matter • Chemistry is the study of matter. • Atoms – basic unit (building block) of matter • 100 million atoms side by side would make a row about 1 cm long (width of a pinkie finger)

5. Nature of Matter • Subatomic particles that make up atoms are: • Protons – positively charged • Neutrons – no charge, same mass as protons • Electrons – negative charge and in constant motion surrounding nucleus • Nucleus – center of the atom that contains protons and neutrons

7. Nature of Matter • Atoms are Neutral • Atoms have equal number of electrons and protons • Ex: O has 8e- and 8protons 8e- +8p+ 0 charge • Atomic Number - # of protons in an atom of elements

8. Elements Na Ca N O2 S Ne Fe • Element – pure substance that consists entirely of one type of atom • More than 100 elements are known • 24 are commonly found in living organisms • 92 of which occur naturally.

9. Elements • Each element has a unique name and symbol. • Usually 1 letter capitalized like C for carbon • Some have 2 letters in this case the second is lower case like in Ca for Calcium

10. The periodic table is organized into: • horizontal rows, called periods • vertical columns, called groups.

11. Each individual block in the grid represents an element. The table is called periodic because elements in the same group have similar chemical and physical properties.

13. Daily Practice 10/14/09 • What does the atomic number tell you? • What two subatomic particles must be equal in a cell in order for it to be neutral? • What does the atomic mass tell you? • How do you calculate the number of neutrons? • Just like yesterday find the Atomic #, mass, number of neutrons, and make the electron configuration for Cu

14. Isotopes • Isotopes – atoms of same element that differ in number of neutrons they contain • Isotopes are identified by mass number • Mass Number – sum of protons and neutrons in nucleus of an atom

15. Isotopes • Isotopes – • Protium-1p and mass 1 • Deutrium-1p and 1neutron and mass 2 • Tritium – 1p and 2 neutrons and mass 3 • Isotopes have the same number of e-, all isotopes of elements have the same chemical properties

17. Radioactive Isotopes • Nuclei are unstable and break down at a constant rate over time. • Uses • Determine ages of rocks and fossils • Treat cancer and kill bacteria that causes food to spoil • Used as tracers to follow movements of substances with in organisms

18. When a nucleus breaks apart, it gives off radiation that can be detected and used for many applications

19. COMPOUNDS • A pure substance formed when two or more different elements combine • Compounds are always formed from a specific combination of elements in a fixed ratio. • Compounds cannot be broken down into simpler compounds or elements by physical means. H2O → 2:1→ 2:H and 1:O NaCl → 1:1 → 1:Na and 1:Cl

20. Chemical Bonds • Ionic Bonds – formed when one or more e- are transferred from one atom to another. • That means there is an electrical attraction between two oppositely charged atoms or groups of atoms • Ion – positively and negatively charged atoms • Na Cl

22. Some atoms tend to donate or accept electrons more easily than other atoms. • The elements identified as metals tend to donate electrons. • The elements identified as nonmetals tend to accept electrons. • Most ionic compounds are crystalline at room temperature and have higher melting points than molecular compounds formed by covalent bonds.

23. Chemical Bonds Conti. • Covalent Bond – formed when e- are shared between atoms. • Atoms share 2e- = single covalent bond • H2O

24. Chemical Bonds Conti. • Atoms share 4e- = double covalent bond • O2 • Atoms share 6e- = triple covalent bond • N2 • Molecule – is a compound that is held together with covalent bonds. • Diatomic Molecules – molecules are made of 2 of the same atoms • H2, O2, N2, F2,Cl2 , Br2, I2

25. Chemical Bonds Conti. Pg 155 • Van der Waals Forces – slight attraction that develops between oppositely charged regions of nearby molecules. • Van der Waals forces are not as strong as ionic or covalent bonds, they can hold molecules together, especially when molecules are large. • The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons.

26. Section 6.2 Chemical Reactions Objectives Identify the parts of a chemical reaction. Relate energy changes to chemical reactions. Summarize the importance of enzymes in living organisms.

27. Chemical Reactions and Enzymes • Chemical Reaction – process that changes one set of chemicals into another set of chemicals. (That is they are reorganized into different substances) • Ex: Fe + O2 → FeO2 (rust – slow process) • Ex: 2H2O → H2 + O2

28. Chemical Reactions and Enzymes • Clues that a chemical reaction has taken place include the production of heat or light, color change and formation of a gas, liquid, or solid.

29. Chemical Reactions and Enzymes • Reactant – elements or compounds that enter into chemical reaction • Ex: Fe + O2 and 2H2O • Product – elements or compounds produced by chemical reaction • Ex: FeO2 and H2 + O2 • Lab Demo – Baking Soda

30. Balanced Equations • The law of conservation of mass states matter cannot be created or destroyed. • The number of atoms of each element on the reactant side must equal the number of atoms of the same element on the product side.

32. Energy in Reactions • Energy is released or absorbed when chemical bonds form or break • Chemical reactions releasing energy occur spontaneously • 2H2 + O2 → 2H2O • H gas burning with O2 = water vapor with energy released in form of heat and if H explodes = light and sound • Humans release energy needed to grow, breathe, think, metabolize, break down food, or digest food

33. Energy in Reactions • Chemical Reactions absorbing energy will not occur without source of energy • 2H2O → H2 + O2 • Absorbs energy and must have electric current going through water • Plants get energy by trapping and storing energy from the sun • Animals get energy when they eat plants or animals that eat plants • Activation Energy – energy needed to get reaction started • Lighting a match to burn trash

34. Energy in Reactions • Activation Energy – energy needed to get reaction started • Lighting a match to burn trash

35. Energy in Reactions • This reaction is exothermic and released heat energy. • The energy of the product is lower than the energy of the reactants.

36. Energy in Reactions • This reaction is endothermic and absorbed heat energy. • The energy of the products is higher than the energy of the reactants.

37. Enzymes • Catalyst – substance that speeds up rate of chemical reaction or lowers reaction’s activation level • It does not increase how much product is made. • A catalyst is not used up in a reaction.

38. Enzymes Cont. • Enzymes – proteins that act as biological catalysts • Cells use enzymes to speed up chemical reactions that take place in cells and lowers activation energy • P. 51 graph • Carbonic anhydrase, enzyme in bloodstream that speeds up reaction to remove CO2 (Carbon Dioxide) from blood

39. Enzyme Action • For chemical reactions to occur then reactants must collide with energy so bonds will be broken and new bonds formed • The reactants that bind to the enzyme are called substrates – (they help catalyzed reactants) • Substrates (protein) that attach to enzyme at active site and form an enzyme – substrate complex

40. Enzyme Action • The specific location where a substrate binds on an enzyme is called the active site. • Proteins have a specific shape, so an active site must be complementary • Compared to a lock and key model

41. The active site changes shape and forms the enzyme-substrate complex, which helps chemical bonds in the reactants to be broken and new bonds to form.

42. Enzyme Action • When complex is formed, enzyme helps convert substrate into product until done and then they are released • Most cells contain proteins that turn key enzymes on or off, along with pH and temperature • Human cells work best at 37⁰, human body’s core temperature

43. Section 6.3 Water and Solutions Objectives Evaluate how the structure of water makes it a good solvent. Compare and Contrast solutions and suspensions. Describe the difference between acids and bases.

44. Properties of Water • Water • Covers ¾ of Earth • Single most abundant compound in most living things • Expands as it freezes and is less dense than liquid water explaining why it floats

45. Properties of Water Conti. • Water Molecules • H2O = 2protons H + 8protons O = 10 protons 2e- H + 8e- = 10e- 10protons + 10 e- = 0 (neutral) • Polarity • Water molecule is polar because there is uneven distribution of e- between H and O2 atoms/ • Between molecules is a magnet with poles • O2 end has negative charge and H end has + charge

47. Hydrogen Bonds • A hydrogen bond is a weak interaction involving a hydrogen atom and a fluorine, oxygen, or nitrogen atom • Cohesion – attraction b/w molecules of same substance • Water molecules can have up to 4 H bonds at the same time • Cohesion is why drops of water form beads on smooth surfaces

48. Hydrogen Bonds • Adhesion – attraction b/w molecules of different substances • Water in graduated cylinder dips at center b/c adhesion b/w glass and water molecules are stronger than cohesion of water molecules • Capillary action – forces draws water out of plant rot up to stems and leaves

49. Solutions and Suspensions • Mixture – material composed of 2 or more elements or compounds that are physically mixed together but not chemically combined. • Ex: vegetable soup, salt and pepper, Earth’s atmosphere gases

50. Homogenous Mixtures • A mixture that has a uniform composition throughout • A solvent is a substance in which another substance is dissolved. • A solute is the substance that is dissolved in the solvent. Food coloring dissolved in water forms a homogenous mixture.