1. Chapter 2

2.  The atom is the basic unit of all matter.  The Greek word atomos, which means “unable to be cut,” was first used to refer to matter by the Greek philosopher Democritus nearly 2500 years ago.  He called the smallest fragments that make up things the atom.

3.  Atoms are made of subatomic particles:  Protons ◦ Positive charge (+)  Neutrons ◦ No charge ◦ Protons and neutrons make up the nucleus (center of the atom)  Electrons ◦ Negative charge (-) ◦ Move around the nucleus.

5.  Electrons are in constant motion around the nucleus.  Electrons (-) are attracted to the protons (+) in the nucleus but remain outside the nucleus because of the energy of their motion.  Atoms have equal numbers of protons and electrons.  The opposite charges cancel each other out so that an atom has a neutral charge.

6.  A chemical element is a pure substance that consist entirely of one type of atom.  There are 100 known elements.  Only approx. two dozen elements are commonly found in living organisms.  The number of protons in an atom is expressed as the elements atomic number.  The number of electrons in an atom is equal to the number of protons in the nucleus.

8.  Atoms of the same element that differ in the number of neutrons they contain are called isotopes.  Isotopes are identified by their mass number (the number of protons and neutrons in the nucleus).

9.  The weighted average of the masses of an element’s isotopes is called its atomic mass.  “Weighted” means the abundance of the isotope in nature.  Because all isotopes have the same number of electrons, all isotopes of an element have the same chemical properties.

10.  Some isotopes are radioactive, meaning that their nuclei are unstable and break down at a constant rate over time.  The radiation these isotopes give off can be dangerous, but radioactive isotopes have a number of important scientific and practical uses.

11.  A chemical compound is a substance formed by the chemical combination of two or more elements in definite proportions.  In nature, most elements are found combined with other elements in compounds  H 2 O  NaCl  CO  CO 2

12.  The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.  Examples  H + O H 2 O  Na + Cl NaCl

13.  The atoms in compounds are held together by chemical bonds.  Bond formation involves the electrons that surround each atomic nucleus.  The electrons that are available to form bonds are called valence electrons.  The main types of chemical bonds are ionic bonds and covalent bonds.

14.  Formed when one or more electrons are transferred from one atom to another.  The positively or negatively charged atoms are called ions.

15.  Formed with electrons are shared between atoms.  The structure resulting when atoms are joined together by covalent bonds are called molecules.  A molecule is the smallest unit of a compound.

16.  Intramolecular forces of attraction between molecules due to the attraction that can develop between oppositely charged regions of nearby molecules.

17.  Section 2 – The properties of water

18.  A substance is matter that has the same fixed composition and properties.  A substance cannot be broken down into simpler parts by ordinary physical processes (boiling, grinding, filtering).  Only a chemical process can change a substance into one or more new substances.  An element is an example of a pure substance.

19.  A compound is made of two or more elements that are chemically combined.  Compounds have a fixed composition.  The ratio of atoms in a compound is always the same.

20.  Water is a substance because it stays the same chemically when frozen or boiled.  Water is also a compound.

21.  Water is often the solvent for many solutions.  A solution in which water is the solvent is called an aqueous solution.  Water is often referred to as the universal solvent.

22.  The sharing of electrons is called covalent bonding.  Compounds that have covalent bonds are called molecular compounds (molecules).

23.  There is an even distribution of electrons in a non- polar covalent molecule.  The atoms share electrons.  The bonds between atoms are called non-polar covalent bonds.

24.  There is an uneven distribution of electrons in a polar molecule  Atoms share electrons.  The bonds between atoms are called polar covalent bonds.  Water is a molecule with polar covalent bonds.

25.  In some atoms the electrons are not shared.  The atoms will either gain or lose electrons.  The number of protons and electrons in the atoms becomes unequal.  The atom takes on a positive or negative charge.  Atoms with a charge are called ions.

26.  Bonds between ions that are formed by the transfer of electrons are called ionic bonds.

27.  Remember, water has positive and negative charges parts.  Positive part will attract negative ions.  Negative part will attract positive ions.  When an ionic compound is mixed with water, the different ions are pulled apart by the water molecule.

28.  Water can dissolve molecular compounds.  However, the water does not break the molecule apart, but moves between the molecules.  The water separates the molecules of the compound.

29.  This means that polar solvents dissolve polar solutes and non-polar solvents dissolve non- polar solutes. ◦ Sugar and water: both are made up of polar molecules ◦ Salt and water: Na and Cl ion pair is similar to the water molecule, both having + and - charges  If a solvent and solute are not similar, the solute will not dissolve. Non-polar molecules will not dissolve polar molecules. ◦ Oil and water

30.  Cohesion is an attraction between molecules of the same substance.  Because of hydrogen bonding, water is extremely cohesive.  Water’s cohesion causes molecules on the surface of water to be drawn inward.

31.  Adhesion is an attraction between molecules of different substances.

33.  Mixtures are combinations of substances that are not bonded together.  The substances can be separated by physical processes.  Mixtures do not always contain the same proportions of the substances.

34.  In a heterogeneous mixture the substances are not mixed evenly.  Different areas of the mixture have different compositions.

35.  A homogeneous mixture contains two or more substances that are evenly mixed on a molecular level but the substances are not bonded together.  A homogeneous mixtures can also be called a solution.

36.  The formation of a solution requires that a solute be dissolved in a solvent.  A solute is the substance that disappears when added to another substance.  The solvent is the substance that dissolves the solute.

37.  A suspension is a mixture of water and non-dissolved material.  Blood ◦ Water ◦ Dissolved compound ◦ Un-dissolved particles ◦ Cells

38.  pH is a measure of how acidic or basic a solution is and relates to the concentration of hydronium ions and hydroxide ions.

39.  The pH scale ranges from 0 to 14.  Acidic solutions have pH values below 7. ◦ A solution with a pH of 0 is very acidic.  Hydrochloric acid has a pH of 0.  A solution with a pH of 7 is neutral, meaning it is neither acidic or basic. ◦ Pure water is neutral.  Basic solutions have pH values above 7. ◦ A solution with a pH of 14 is very basic.  Sodium hydroxide can have a pH of 14.

40.  The strength of an acid is related to how easily the acid separates into ions, or how easily a hydrogen ion is released when the acid dissolves in water.  More hydronium ions means the strong-acid solution has a lower pH than the weak-acid solution.  The pH of a solution is more acidic when greater amounts of hydronium ions are present.

41.  The strength of a base is related to how easily the base separates into ions, or how easily a hydroxide ion is released when the base dissolves in water.

42.  Buffers are weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH.

43. Section 3:Carbon compounds

44.  Carbon atoms have four valence electrons. ◦ Each electron can join with an electron from another atom to form a strong covalent bond.  Carbon can bond with other carbon atoms. ◦ Gives carbon ability to form chains of unlimited length.  Carbon-carbon bonds can be single, double, or covalent bonds.

45.  Large molecules.  Made from thousands of smaller molecules.  Macromolecules are formed by process called polymerization. ◦ Large compounds built by joining smaller molecules together. 

46.  Organic compounds are classified into groups.  Four groups of organic compounds found in living things: ◦ Carbohydrates ◦ Lipids ◦ Nucleic acids ◦ Proteins

47.  Compounds made of carbon, hydrogen, and oxygen atoms.  Ration of 1:2:1  Living things use carbohydrates as their main source of energy.

48.  Simple sugars.  Galactose – component of milk.  Fructose – found in many fruits.

49.  Large macromolecules formed from monosaccharides.  Glycogen ◦ Referred to as animal starch. ◦ Stored in liver. ◦ Stored in muscles.

50.  Polysaccharide called plant starch (stored excess sugar).  Cellulose – tough, flexible fibers that give plants their strength and rigidity.

51.  Large macromolecules made mostly of carbon and hydrogen atoms.  Not soluble in water.  Can be used to store energy.  Steroids are lipids. ◦ Serve as chemical messengers.

52.  Fatty acids that contain the maximum possible number of hydrogen atoms are called saturated lipids.

53.  Lipids with fatty acids that contain more than one double bond are referred to a polyunsaturated lipids.

55.  Macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus.  Polymers assembled from individual monomers known as nucleotides.  Nucleotides consist of a 5-carbon sugar, a phosphate group, and a nitrogenous base.  Individual nucleotides can be joined by covalent bonds to form a polynucleotide (nucleic acid).

56.  Nucleic acids store and transmit hereditary, or genetic information.  Ribonucleic acid (RNA)  Deoxyribonucleic acid (DNA)

57.  Macromolecules that contain nitrogen, carbon, hydrogen, and oxygen.  Polymers of molecules called amino acids.  Amino acids are compounds with an amino group (-NH2) and a carboxyle group (-COOH).  More than 20 different amino acids found in nature.  Function of proteins – control rate of reactions, regulate cell processes, form bones and muscles, transport substances into or out of cells to help fight disease.

58.  Four levels of organization: ◦ First - Sequence of amino acids in a protein chain. ◦ Second – Amino acids within a chain that can be twisted or folded. ◦ Third – The chain of amino acids itself is folded. ◦ Fourth – More than one chain of amino acids with each chain having a specific arrangement.

61.  Everything that happens in an organism—its growth, its interaction with the environment, its reproduction, and even its movement—is based on chemical reactions.  A chemical reaction is a process that changes one set of chemicals into another set of chemicals.

62.  The elements or compounds that enter into a chemical reaction are known as reactants.  The elements or compounds produced by a chemical reaction are known as products.

64.  Important chemical reaction that occurs in your body involves carbon dioxide (CO2). Your cells constantly produce carbon dioxide. This carbon dioxide is carried to your lungs through the bloodstream. As CO2 enters the blood, carbon dioxide reacts with H2O to produce a highly soluble compound called carbonic acid, H 2 CO 3. CO 2 + H 2 O → H 2 CO 3  The reaction shown above enables the bloodstream to carry carbon dioxide to the lungs. In the lungs, the reaction is reversed. H 2 CO 3 → CO 2 + H 2 O  This reverse reaction produces carbon dioxide gas, which is released as you exhale. and then is eliminated as you exhale.

65.  Energy changes  Energy is released or absorbed whenever chemical bonds form or are broken. Because chemical reactions involve breaking and forming bonds, they involve changes in energy.  Chemical reactions that release energy often occur spontaneously. Chemical reactions that absorb energy will not occur without a source of energy

66.  Activation energy  The energy that is needed to get a reaction started the activation energy.  Chemical reactions that release energy often occur spontaneously.  Chemical reactions that absorb energy will occur only with a source of energy

67.  A catalyst is a substance that speeds up the rate of a chemical reaction. Catalysts work by lowering a reaction's activation energy.  Enzymes are proteins.  Enzymes speed up chemical reactions that take place in cells.  Enzymes act by lowering the activation energies, as illustrated by the graph below.  Lowering the activation energy has a dramatic effect on how quickly the reaction is completed.

69.  For a chemical reaction to take place, the reactants must collide with enough energy so that existing bonds will be broken and new bonds will be formed. If the reactants do not have enough energy, they will be unchanged after the collision.  Enzymes provide a site where reactants can be brought together to react. Such a site reduces the energy needed for reaction.  The reactants of enzyme-catalyzed reactions are known as substrates.

71.  Regulation of enzyme action ◦ pH ◦ Temperature