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Chapter Two: Matter Matter Atom-basic unit of matter 1. Subatomic particles- protons, neutrons, electrons A. Protons- positive charge, center of atom (nucleus) B. Neutron- neutral, center of atom C. Electrons- negative charge, in constant motion around nucleus Matter Elements- pure substance that consists entirely of one type of atom 1. Represented by symbol 2. Atomic number- number of protons in an atom Number of protons = number of electrons 3. Atomic mass- protons and neutrons A. Number of neutrons = atomic mass – atomic number Matter 4. Electron Cloud- area around nucleus where electrons are orbiting 1st level- holds 2 electrons 2nd level- holds 8 electrons 3rd level- holds 8 electrons 4th level- holds 18 electrons Example 17 Cl 35.453 atomic number symbol mass number Atomic number: Atomic mass: Number of protons: Number of neutrons: Number of electrons: Isotopes- atoms that have an equal number of protons but different number of neutrons Radioactive isotopes- nuclei are unstable and break down at a constant rate over time Geologists determine age of rocks and fossils by analyzing the isotopes in them Radiation from some isotopes are used to treat cancer Used as tracers Compounds- substance formed by the chemical combination of two or more elements in definite proportions Example – H2O Chemical Bonds Valence electrons- electrons that are available to form bonds Ionic bonds- when one or more electrons are transferred from one atom to another Example- NaCl Covalent bond- forms when electrons are shared between atoms Example- H2O Ions- positive or negative charged atom Positive charge= lose an electron Negative charge = gain an electron Molecules- the smallest unit of most compounds, the structure that results when atoms are joined together by covalent bonds Subscript- number of atoms Coefficient- number of molecules of a compound element number of atoms H2O 2H2O2 Van derWaals Foreces- when molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules Example: Geckos Physical Changes: change in form of substance not the chemical makeup Ex: size, shape, states of matter Chemical changes- a substance changes into a new substance Example: rusting, digesting, rotting Properties of Water Most abundant compound in living things Covers ¾ ‘s of Earth’s surface Expands when it freezes so ice is less dense than liquid water Water molecule- neutral 1. polarity- an uneven sharing of electrons between the O and H atoms Example: DRAW A WATER MOLECULE 3. Hydrogen bonds Water can have as many as four H bonds at the same time A. cohesion- attraction between molecules of same substance Surface tension- the force that occurs because of cohesion Example- insect walk on water, drops of water form beads on smooth surface B. adhesion- attraction between molecules of different substances Example- meniscus- the adhesion between water molecules and graduated cylinder are stronger than the cohesion between water molecules 1. Capillary action- adhesion causes H20 to rise in a narrow tube A. Example- draw H20 out of roots of plant and up into the stem and leaf B. Solutions and Suspensions 1. Mixture- a material composed of two or more elements or compounds that are physically mixed together but not chemically combined Example- salt and pepper, sugar water A. Solution-mixture of two or more substances in which the molecules of the substances are evenly distributed 1. Example- Salt water Solute- the substance that is dissolved (salt) Solvent- the substance in which the solute is dissolved (water) H2O- the greatest solvent of Earth B. Suspensions- mixture of water and undissolved materials C. Acids, Bases, pH 1. pH scale- indicates the concentration of H ions in solution A. 0-14 pH 7 = neutral, concentration of H ions and OH ions are equal Example- pure water pH below 7= acidic, more H ions than OH ions pH above 7= basic, more OH ions than H ions Basic C. Acids, Bases, pH 2. Acids- a compound that forms H ions in solution pH of 1-3 = strong acid Example- HCl 3. Bases- compound that produces hydroxide (OH) pH of 11-14 = strong base Example- lye , NaOH III. Carbon Compounds Organic Chemistry- study of all compounds that contain bonds between carbon atoms A. Chemistry of carbon 1. carbon atoms can bond to other carbon atoms to form very long chains B. Macromolecules- very large molecules 1. monomers- smaller unit that can join together with other small units to form polymers 2. polymers- large compound formed from combinations of many monomers 3. Dehydration synthesis The formation of a chemical bond by removing a water molecule 4 types of macromolecules: Carbohydrates Lipids Nucleic acids Protein Carbohydrates: compounds made up of C, H, O atoms in a 1:2:1 ratio A. living things use carbohydrates as their main source of energy B. living things store extra sugar as starch (long chains of sugar molecules ) C. monosaccharides- single sugar molecules Ex: glucose, galactose (milk), fructose (fruit) Disaccharides- sugars made up of two covalently bonded monosaccharides Ex: sucrose (table sugar), lactose (milk sugar) D. polysaccharides- large macromolecules formed from monosaccharides Example: glycogen (animal starch), causes muscle contractions Example: cellulose- tough fibers that give plants much of their strength and rigidity. Major component of wood and paper 2. Lipids Macromolecules made mostly of carbon and hydrogen atoms and are not soluable in H2O A. stores energy, waterproof coverings, steroids B. example- fats, oils, waxes 2 types: 1. saturated- solid at room temp Example: butter 2. unsaturated- liquid at room temp Example: olive oil 3. Nucleic Acids Macromolecules that contain H, O, N, C, and P which are formed from Nucleotides (Page 47) A. nucleotide (monomer)- consists of sugar, phosphate, nitrogen base B. Store and transmit genetic info C. 2 kinds DNA – deoxyribose nucleic acid sugar = deoxyribose RNA- ribonucleic acid sugar = ribose 4. Protein Polymers of amino acids which are made of N, C, H, O. They control rate of reactions, build bones and muscles A. 20 different amino acids B. instructions for arranging amino acids into different proteins which are stored in DNA C. each protein has a specific role D. have an amino group (-NH2) on one end, a carboxyl group (COOH) on the other end and an R group. The R group makes proteins different. IV. Chemical Reactions and Enzymes A. Chemical reactions- process that changes one set of chemicals into another Example: Iron (Fe) + O H+ O rust H2O Reactants- what you start with Products- what’s produced Subscript B. Energy Changes 1. Chemical reactions release energy- exothermic A. occur spontaneously B. energy released in form of heat 2. Chemical reactions that absorb energy- Endothermic A. will not occur without a source of energy B. in plants, the energy comes from sun in animals, the energy comes from food Activation Energy and Catalysts C. Activation Energy -the energy needed to get a reaction started D. Catalysts- substance that speeds up the rate of a chemical reaction 1. Catalysts lower a reaction’s activation energy Enzymes- proteins that act as biological catalysts to speed up chemical reactions in cells A. substrate- reactant of an enzyme- catalyzed reaction B. Substrates bind to a site on the enzyme called the active site C. Enzyme-Substrate Complex- the enzyme and substrate comes together to form this D. “Lock and Key” model- the fit of the enzyme and the substrate is so precise that the fit is often referred to as this
