Science Midterm

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Science Midterm by Mind Map: Science Midterm

1. Chapter 3: Different Forms of Energy

1.1. Energy

1.1.1. Law of conservation of energy energy can neither be created nor destroyed, it can only be transferred or transformed. The total amount of energy in an isolated system always remains constant

1.1.2. energy efficiency the percentage of energy consumed by a machine or system that was transformed into useful energy Energy efficiency = useful energy/energy consumed X 100

1.1.3. Forms of energy Radiation energy contained in and transported by electromagnetic waves Chemical energy Energy stored in molecular bonds Wind energy Energy resulting from the movement of the air

1.1.4. Thermal energy the energy contained in a substance determined by the number of particles in it and their temperature Heat transfer of thermal energy between the environments with different temperatures always passes from a warmer to a cooler environment Temperature a measure of the degree of agitation of particles of a substance Specific heat capacity amount of thermal energy required to raise the temperature of one gram of a substance by one degree celcius Q = ∆Et Q= Heat (in Joules) ∆Et = variation in thermal energy Q = mc∆T Q =Heat (or heat variation in thermal energy) m = Mass c = Specific heat capacity ∆T = Temperature variation

2. Chapter 4: Changes in Matter

2.1. Chemical Changes

2.1.1. Signs indicating chemical change release of gas emission of absorption of heat emission of heat emission of light change in colour unexpected formation of precipitate

2.1.2. Law of conservation of mass total mass of reactants is always equal to the total mass of products

2.1.3. Balancing chemical equations consists of placing a coefficient before each reactant and product so that the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side Rules to apply when balancing an equation: Coefficients must be whole numbers Coefficients must be as small as possible new substances must never be added existing substances must never be removed subscripts on elements never change the final equation should be checked by counting the number of atoms of each element

2.1.4. Stoichiometry the study of the quantities of reactants required for chemical reactions to occur and the quantities that are thus formed

2.1.5. Endothermic, Exothermic reactions endothermic a chemical change that absorbs energy exothermic a chemical change that releases energy reaction energy: the amount of energy absorbed or released by a reaction can be calculated by finding the difference between the energy absorbed when the bonds between the atoms of the reactants break and the energy released when the bonds between the atoms of the products form. Reaction Energy = Energy of reactants -Energy of products

2.1.6. Types of chemical change (reactions) Synthesis A + B --> AB Decomposition AB --> A + B Precipitation AB + CD --> AD + CB Acid Base Neutralization chemical change involving the reaction of an acid with a base, producing a salt and water Acid(aq) + Base(aq) --> Salt(aq) + Water(l) Oxidation chemical change involving oxygen or a substance with properties similar to those of oxygen Combustion Cellular Respiration chemical change in which glucose and oxygen are used to generate energy also produces water and CO2 opposite of photosynthesis C6H12O6 + 6O2 ---> energy + 6CO2 + 6H2O Photosynthesis chemical change that produces glucose and oxygen from carbon dioxide, water and solar energy in the presence of chlorophyll opposite of cellular respiration 6CO2 + 6H2O + solar energy (in the presence of chlorophyll) -----> C6H12O6 + 6O2

3. Chapter 1: Atoms & Elements

3.1. All Atomic Models

3.1.1. Dalton atoms = solid, indivisible balls of different masses

3.1.2. Thompson discovered electron plum pudding model: positively charged ball embedded with small negatively charged particles

3.1.3. Rutherford gold foil experiment discoveries points alpha radiation to piece of gold foil to see whether or not they bounce back results: most passed through the gold foil, some bounced back

3.1.4. Rutherford-Bohr discovers electrons in specific orbits electrons can jump back and forth from orbits

3.1.5. Chadwick (simplified) discovers neutron neutrons must be present to hold the protons together in the nucleus model in nucleus in electron shells

3.2. Periodic Table

3.2.1. metals, nonmetals, metalloids metals good conductors of heat and electricity usually shiny ductile malleable solid at room temperature (except mercury) nonmetals bad conductors of heat and electricity usually gas at room temperature metalloids depending on conditions used to make semiconductors

3.2.2. groups alkali metals first column of periodic table highly reactive found in elemental state of nature alkaline earth metals second column of periodic table highly malleable highly reactive burn in the presence of heat hallogens second to last column of periodic table react easily noble gases last column of periodic table very stable react very minimally

3.2.3. periods and periodicity Period row of periodic table periodicity repetition of patterns from one period to another

3.2.4. atomic number number of protons in nucleus of an atom distinguishes one element from another

3.2.5. relative atomic mass mass of an atom measured by comparison with a reference element carbon-12

3.2.6. mass number WHOLE NUMBER indicates the sum of numbers of protons and neutrons in an atom Symbol: A AZE Notation

3.2.7. isotopes and neutrons isotope an isotope is an atom of an element with the same number of protons as another atom but a different number of neutrons

3.3. Atomic Representation

3.3.1. Lewis Notation representation of the atom where only the valence electrons are illustrated Ex: Fluorine

3.3.2. Rutherford-Bohr period indicates number of electron shells group indicates number of valence electrons atomic number indicates number of protons and number of electrons

3.3.3. Simplified Atomic model EX: Chlorine

3.3.4. Ball and Stick model EX: H2O

3.4. Moles, Molar Mass, Avogadro's Number

3.4.1. Moles Quantity equal to the number of atoms in exactly 12g of Carbon-12 Symbol: mol

3.4.2. Molar Mass mass of one mole in a substance formula: M=m/n M=Molar Mass (g/mol) m=mass (g) n=number of moles (mol)

3.4.3. Avogadro's Number number of entities in a mole 6.02 x 10^23

4. Chapter 2: Molecules and Solutions

4.1. Molecules

4.1.1. Ions and Polyatomic Ions ions atoms that are no longer neutral number of protons stay the same number of electrons changes NEGATIVE IONS POSITIVE IONS Polyatomic Ions either negatively or positively charged group of two or more chemically bonded atoms that has become electrically charged by losing or gaining one or more electrons ex: SO4

4.1.2. Nature of Chemical Bonds ionic bonds bond between an atom that wants to lose electrons and an atom that wants to gain electrons metal + nonmetal ex: Na + Cl covalent bonds sharing of one or more electron pairs between atoms 2 nonmetals (nonmetal + nonmetal) Ex: Fluorine ex: Oxygen

4.1.3. Rules of Chemical notation and nomenclature rules of notation order of symbols add subscripts after symbols to specify numbers of atoms or ions of each element in molecule rules of nomenclature Name first element Change name of second element accordingly (for covalent bonds only) add prefixes to specify the number of atoms of each element (for ionic formulas only) the positive ion precedes the negative ion

4.2. Properties of Solutions

4.2.1. Solubility maximum amount of solute that can be dissolved in a certain volume of solvent

4.2.2. concentration amount of solute in a given amount of solution C=m/v %m/v Xg / 100ml Dilution adding solvent Dissolution adding solute concentration in ppm "parts per million" parts of solute in a million parts of solution molar concentration number of moles in a liter of solution C = n/v

4.2.3. Electrical conductivity = measure of the ability of a solution to allow an electric current to flow through it Electric dissociation the separation of a dissolved compound into two ions of opposite charges only works with elecrolytes electrolyte substance that when dissolved in water, allows an electric current to flow through the solution types of electrolytes

4.2.4. release a positive ion as well

4.2.5. pH scale ranges from 1-14