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Chemistry Midterm

Accelerated Chemistry Midterm 2013

What is matter? Anything that has mass and takes up space - found in solids, liquids, and gases
What is mass? A measurement that reflects the amount of matter
What is density? The mass of a substance proportional to each unit of volume
Density equations D=M/V V=M/D M=D*V
Density of water 1 gram/1 mililiter
What is a chemical change? Process involving 1 or more substances changing identity of reactants
Four indications of a chemical change 1. Color change 2. Formation of gas (bubbles or odor) 3. Formation of precipitate (solid) 4. Release of energy (light, heat, sound)
Examples of a chemical properties Rusting, explosion, rotting, decomposition, cooking
What is a physical change? Alters physical properties of a substance but does not change identity
Examples of physical properties Changes in color, mass, size, form, state; dissolving
Properties of a SOLID - Has a definite volume and shape - Slow-moving particles that are tightly packed - Constantly moving particles - Expands when heated; incompressible - Constant vibrations of particles at atomic level - Lowest kinetic energy - One swooshy
Properties of a LIQUID - Definite volume with indefinite shape - Takes shape of container - Particles slide past each other (flow) - Particles less closely packed than solid - Expands when heated; incompressible - Moderate kinetic energy - Two swooshies
Properties of a GAS - No definite shape or volume - Conforms to shape of its container and takes up whole container - Particles very far apart - Compressible - Highest kinetic energy - Three wooshies
Define pure substance Matter that has distinct properties and a composition that does NOT vary from sample to sample; cannot be physically separated because its made up of one type of atom
Define element A pure substance that cannot be separated into simpler substances by physical or chemical means, made all of one type of element
Define compound Made up of 2 or more elements that are combined chemically; properties are different that those of its component elements
What is a mixture? A combo of 2 or more substances in which each pure substance retains its individual chemical properties - can be physically separated into its components
What are heterogeneous mixtures? Do not blend smoothly throughout and the individual components remain distinct
What are homogeneous mixtures? Constant composition throughout and always has a single phase
Solutions are what? HOMOgeneous mixtures
The scientific method is... A systematic approach used in scientific study and is repeated until a hypothesis is supported/discarded
Steps to the scientific method 1. Problem/Question 2. Observation/Research 3. Hypothesis 4. Experiment 5. Collect and Analyze results 6. Conclusion 7. Communicate results
What is the independent variable? Variable that IS changed in an experiment
What is the dependent variable? Variable that changes in response to dependent variable
What is a hypothesis? Tentative explanation for observations
What is the control? Serves as a standard for comparison
What are the constants? Variables that do not change in the experiment in order to make the independent variable changed
What is the uncertainty? - It is half of the line of measurement - Used because of limitations of humans/instruments i.e. if lines were 0.1 cm, measurement could be 0.35 ± 0.05 cm.
What is accuracy? How close a measured value is to an accepted value
What is precision? How close a series of measurements are to one another
How can mixtures be separated? Physically separated by filtration, distillation, crystallization, sublimation, chromatography
Heating and cooling curves @ Plateaus - thermal energy transfers to phase account/constant thermal energy allows heat to increase @ Inclines - Phase energy is stored/constant thermal energy just heats the phase
Thermal energy Energy stored in moving particles - when full, energy goes into phase account (@ plateau)
Phase energy Energy stored due to attractions between particles - decreases energy of a system and more tightly bound = lower phase energy
Energy calculations for solid/liquid/gas Q=mc(delta)T Q=energy m=mass c=heat capacity (which are given to us)
Energy calculations for fusion/vaporization Q=mHf or Q=mHv Q=energy m=mass Hf or Hv=heat of fusion/vaporization (given)
Changes in state by... Melting, freezing, vaporization, condensation, sublimation, deposition
Democritus Proposed matter is not divisible and made of "Atomos"
Dalton's Atomic Theory (1-3 of 6) 1. All matter = atoms 2. Atoms = indivisible and indestructible 3. All atoms of one element are identical in size, mass, chemical properties
Dalton's Atomic Theory (4-6 of 6) 4. Atoms of one element are different from atoms of another element 5. Different atoms combine in simple whole number ratios to form compounds 6. In a chemical reaction atoms are separated, combined, rearranged
Dalton's Laws Law of Conservation of Mass Law of Definite Proportions Law of Multiple Proportions
Dalton's Model of the Atom Simply a solid sphere with a neutral charge
Revisions to Dalton's Theory (3) 1. Atoms are divisible (subatomic particles) 2. Atoms are destructible 3. All atoms of a given element are not identical (ions and isotopes)
Thomson The mass of an electron is negligible and does not contribute to the mass of the element
Thomson's Plum Pudding Model of the Atom A solid sphere with a + charge embedded with electrons with a - charge that form a neutral-charged atom
Rutherford Discovered the nucleus, very dense and + charge
Rutherford's Model of the Atom Mostly empty space which electrons move, has a nucleus and alpha particle path
Thomson's experiments - Used the cathode ray tube, concluded that particles have mass to move paddle wheel - Put an object in the path of the ray cast a shadow, concluded that light has particles moving in a straight line - Magnet and proved the cathode had a negative charge
Rutherford's gold foil experiment 1. Most particles went straight through, atom is mostly empty space 2. Some particles went through at an angle 3. 1/800 aparticles hit dead on a very small, dense positively-charged nucleus and shot back
Bohr's Model of the Atom A quantum model for the hydrogen atom with one single electron and energy states (ground and excited)
Define atom The smallest unit of matter that retains all properties of that element
The nucleus Very dense, positive, contains protons/neutrons, determines mass
Empty space is Rutherford's Model Empty space surrounded the nucleus and elections were inside
Empty space in Bohr's Model Empty space between electron orbitals as well as the nucleus and first orbital
What is an isotope? Atoms of the same element with a differing number of neutrons (thus different masses)
Atomic number # of protons
Mass number # of protons and neutrons
Alpha - Slow moving because of its size/mass (2 protons and 2 neutrons) - Lowest penetrating power because of its size and motion; stopped with tissue paper
Beta - Faster moving - Charge is -1 - Very small mass - Greater penetrating power; can be stopped by hard tissue
Gamma - Photons with high energy radiation - Highest penetrating power; stopped by lead
Positron Emission Same as an electron but positive - highly unstable, converts back and releases gamma radiation
Percent Error % error = (observed - accepted)/accepted * 100
Fission Splitting of a nucleus into smaller nuclei to form new elements - releases energy to generate electricity in nuclear reactors
Fusion Combines atomic nuclei - produces super heavy elements and 100 times more energy than fission but needs energy from an atomic explosion to start it
Nuclear reactor - Fuel rods made of Uranium fuel the reaction, made to absorb neutrons and be lowered - Water cools the system and is reused - Steam is used to generate electricity
Penetrating power is... The ability of radiation to pass through matter
Slope Is density, is a constant, calculated by D=M/V
Graphing Independent variable = x-axis Dependent variable = y-axis
Created by: BrendanWalters