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Chemistry Midterm
Accelerated Chemistry Midterm 2013
| Question | Answer |
|---|---|
| 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
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