1、Chapter 2 Lecture NotesEssential Chemistry for Biology Biol 100 K. Marr Spring 2007,Topics Discussed in these notesMatter, Elements and CompoundsPeriodic Table of the Elements: Metals vs. NonmetalsAtomic Structure Chemical Bonding: Ionic vs. Covalent BondingChemical Reactions and Chemical EquationsT
2、he Structure of WaterWater as a SolventThe Importance of Water to Living ThingsAcids, Bases and pHSelf-test/Review Questions,Organisms and all other things in the universe consist of matterMatter: Elements and Compounds Matter is anything that occupies space and has mass Matter is composed of chemic
3、al elements and compounds Elements: substances that cannot be broken down into other substances There are 92 naturally occurring elements on Earth What are compounds? Examples?,BASIC CHEMISTRY,Periodic table of the elements,Location of Metals? Nonmetals?,25 Elements are essential to life C, H, O, N:
4、 96% of the weight of the human body,Elements can combine chemically to form compounds Compounds contain two or more elements chemically combined in a fixed ratio Examples of Compounds: Table salt (sodium chloride): NaCl Water: H2O Glucose: C6H12O6,Some Elements React to Form Compounds,Each element
5、consists of one kind of atom,Atom: smallest unit of matter that retains the properties of an element,Fig. 2.02,(a) Hydrogen atom,(b) Carbon atom,(c) Oxygen atom,Proton,Neutron,Electron,Atomic nucleus,First shell,Second shell,The subatomic particles of an atom,Atomic Structure,Proton, Positive charge
6、, Determines element,Neutron, No charge, Determines isotope,Electron, Negative charge, Participates in chemicalreactions, Outer-shell electronsdetermine chemicalbehavior,Nucleus, Consists of neutrons and protons,Elements differ in the number of subatomic particles in their atoms Atomic Number: numbe
7、r of protons determines which element it is Mass number sum of the number of protons and neutrons,Electrons Located outside the nucleus of an atom in specific electron shells (energy levels) The number of electrons in the outermost shell determines the chemical properties of an atom,Chemical Propert
8、ies of Atoms,Atoms of the four elements most abundant in life,Electron,First electron shell: can hold 2 electrons,Outermost electron shell: can hold 8 electrons,Carbon (C) Atomic number = 6,Nitrogen (N) Atomic number = 7,Oxygen (O) Atomic number = 8,Hydrogen (H) Atomic number = 1,Orbital Diagrams of
9、 the First 18 Elements,2,8,8,1st Shell2nd Shell3rd Shell,Chemical reactions: Atoms give up or acquire electrons in order to complete their outer shells Result in atoms staying close together to form molecules Chemical bonds hold molecules together Ionic Bonds Covalent bonds,Chemical Bonding and Mole
10、cules,When an atom loses or gains electrons, it becomes electrically charged Charged atoms are called ions Ionic bonds are formed between oppositely charged ions,Ionic Bonds: form between metals and nonmetals,Sodium atom (Na),Chlorine atom (Cl),Complete outer shells,Sodium ion (Na),Chloride ion (Cl)
11、,Sodium chloride (NaCl),(a) Hydrogen atom (H),(c) Sodium atom (Na),(b) Hydrogen ion (H+),(d) Sodium ion (Na+),1 electron,1 proton,No net electrical charge,11 electrons,11 protons,No net electrical charge,No electron,1 proton,10 electrons,11 protons,Fig. 2.03,Atoms: electrically neutral,Ions: Electri
12、cally charged,A covalent bond forms when two atoms share one or more pairs of outer-shell electrons,Covalent Bonds: form between nonmetallic atoms,Fig. 2.04a,Covalent bonding in water,Full shell with 8 electrons,Slightly negative,Hydrogen atoms with unfilled shells,Full shells with 2 electrons each,
13、+,Slightly positive,+,Covalent bond (shared pair of electron),Oxygen atom with unfilled shell,Water molecule (H2O),Cells constantly rearrange molecules by breaking existing chemical bonds and forming new ones Such changes in the chemical composition of matter are called chemical reactions,Chemical R
14、eactions,Hydrogen gas,Oxygen gas,Water,Reactants,Products,Reactants: on the left side of the equation the starting materials,Chemical Equations: symbolize chemical reactions,Products: on the right side of the equation the ending materials (the stuff produces),Law of Conservation of Mass Chemical rea
15、ctions do not create or destroy matterthey only rearrange it!,Life on Earth began in water and evolved there for 3 billion years The abundance of water is a major reason Earth is habitable Modern life still remains tied to water Your cells are composed of 70%95% water,WATER AND LIFE,The water molecu
16、le: two hydrogen atoms joined to one oxygen atom by single covalent bonds,The Structure of Water,H,O,H,The electrons of the covalent bonds are shared unequally between oxygen and hydrogen unequal sharing of electrons makes water a polar molecule hydrogen atoms: partially positive (d ) Why? oxygen at
17、om: partially negative (d -) Why?,(d ),(d ),(d ),Water: a polar molecule,The polarity of water results in weak electrical attractions between neighboring water molecules These interactions are called hydrogen bonds,(b),(),Hydrogen bond,(),(),(),(),(),(),(),The Structure of Water,The polarity of wate
18、r molecules and the hydrogen bonding that results explain most of waters life-supporting properties Versatility of water as a solvent Waters cohesive nature Waters ability to moderate temperature Floating ice,Waters Life-Supporting Properties,A solution is a liquid consisting of two or more substanc
19、es evenly mixed,Water as the Solvent of Life,The dissolving agent is called the solvent The dissolved substance is called the solute,Ion in solution,Salt crystal,Dissolving of Sodium Chloride (NaCl) in Water,Salt,Water,Electrical attraction,Water molecules (H2O),Hydrogen bonds,Edge of one salt cryst
20、al,Ionic bond,Water molecules dissolve NaCl, breaking ionic bond,Water molecules stick together as a result of hydrogen bonding This is called cohesion Cohesion is vital for water transport in plants,The Cohesion of Water,Microscopic tubes,Surface tension is the measure of how difficult it is to str
21、etch or break the surface of a liquid Hydrogen bonds give water an unusually high surface tension,Figure 2.13,Because of hydrogen bonding, water has a strong resistance to temperature change Water can absorb and store large amounts of heat while only changing a few degrees in temperature Earths Ocea
22、ns cause temperatures to stay within limits that permit life,Water Moderates Temperature,The density of ice is lower than liquid water This is why ice floats,Hydrogen bond,Liquid water,Hydrogen bonds constantly break and re-form,Ice,Stable hydrogen bonds,When water molecules get cold, they move apar
23、t, forming ice A chunk of ice has fewer molecules than an equal volume of liquid water Since ice floats, ponds, lakes, and even the oceans do not freeze solid Marine life could not survive if bodies of water froze solid,The Biological Significance of Ice Floating,Acid A chemical compound that donate
24、s H+ ions to solutions Base A compound that accepts H+ ions and removes them from solution,Acids, Bases, and pH,Basic solution,Neutral solution,Acidic solution,Oven cleaner,Household bleach,Household ammonia,Milk of magnesia,Seawater,Human blood,Pure water,Urine,Tomato juice,Grapefruit juice,Lemon j
25、uice; gastric juice,Acidic: pH OH- Basic: pH 7H+ OH- Neutral: pH = 7H+ = OH-,pH Scale,The pH scale is used to describe the acidity of a solution,Self-test/Review Questions,Use these questions as a self test and then discuss your responses with your study group/classmatesyour responses will not be co
26、llected. Why is carbon dioxide gas, CO2, classified as a compound but nitrogen gas, N2, is not? Which of the following are compounds? Elements?: C6H12O6, CH4, O2, Cl2, HCl, MgCl2, Fe, Ca, Ne, NaI, I What is the difference between an atom and an ion? Give examples of each to support your response. Wh
27、ich subatomic particle determines the identity of an atom? Which subatomic particle determines the chemical properties of an atom?,Self-test/Review Questions,A carbon atom has 6 protons, and the most common isotope of carbon has 6 neutrons. A radioactive isotope of carbon has 8 neutrons. What are th
28、e atomic numbers and the mass numbers of the of the stable and radioactive forms of carbon? Explain the difference between an ionic and covalent bond in terms of what happens to the electrons in the outer shell of the participating atoms. Sodium fluoride, NaF, is often added to toothpaste to both ki
29、ll bacteria that cause cavities. It also helps to harden the enamel of teeth thus helping it resist cavities. Is sodium fluoride an ionic or covalent compound? How do you know? Explain your reasoning. Is carbon dioxide an ionic or covalent compound? How do you know? Explain your reasoning.,Self-test
30、/Review Questions (cont.),Why are the following incorrect structures for the substances below? Rewrite their structures with the correct number of chemical bonds. Carbon dioxide gas: OCO Oxygen gas: OO Nitrogen gas: NN Explain how waters versatility as a solvent results from the fact that water is p
31、olar molecule. A bottle of Pepsi consists mostly of sugar dissolved in water, with some carbon dioxide gas that makes fizzy and makes the pH less than 7. Describe Pepsi using the following terms: solute, solvent, acidic, aqueous solution,Self-test/Review Questions (cont.),Which of the following are
32、chemical changes? Physical changes? If possible, write the balanced chemical equation for those that are a chemical change.The alcoholic fermentation in Yeast in which yeast produce ethanol, C2H5OH, and carbon dioxide, CO2, from the sugar glucose, C6H12O6 Water boils to form steam The healing of a c
33、ut finger Cutting a piece of wood with a saw Potassium metal, K, and chlorine gas (Cl2) combine to form potassium chloride. The rusting of iron, Fe, to produce rust, iron (III) oxide (Fe2O3),Self-test/Review Questions (cont.),Which of these is not a subatomic particle? a) proton; b) ion; c) neutron;
34、 d) electron The outermost electron shell of every Noble Gas element (except Helium) has _ electrons. a) 1; b) 2; c) 4; d) 6; e) 8 An organic molecule is likely to contain all of these elements except _. a) C; b) H; c) O; d) Ne; e) N The chemical bond between water molecules is a _ bond. a) ionic; b
35、) polar covalent; c) nonpolar covalent; d) hydrogen A solution with a pH of 7 has _ times more H ions than a solution of pH 9. a) 2; b) 100; c) 1000; d) 9; e) 90 The type of chemical bond formed when electrons are shared between atoms is a _ bond. a) ionic; b) covalent; c) hydrogen,Self-test/Review
36、Questions (cont.),The type of chemical bond formed when oppositely charged particles are attached to each other is a _ bond. a) ionic; b) covalent; c) hydrogen Carbon has an atomic number of 6. This means it has _. a) six protons; b) six neutrons; c) six protons plus six neutrons; d) six neutrons an
37、d six electrons Each of the isotopes of hydrogen has _ proton(s). a) 3; b) 1; c) 2; d) 92; e) 1/2 A molecule is _. a) a mixture of various components that can vary; b) a combination of many atoms that will have different ratios; c) a combination of one or more atoms that will have a fixed ratio of its components; d) more important in a chemistry class than in a biology class,
