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Questions and Answers
What is a molecule composed of?
What is a molecule composed of?
What occurs when an atom loses electrons?
What occurs when an atom loses electrons?
Which subatomic particles are found in the nucleus of an atom?
Which subatomic particles are found in the nucleus of an atom?
If an atom has more electrons than protons, what is it called?
If an atom has more electrons than protons, what is it called?
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How does the size of an atom's nucleus compare to the overall size of the atom?
How does the size of an atom's nucleus compare to the overall size of the atom?
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Which of the following describes a pure substance?
Which of the following describes a pure substance?
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What is the primary distinction between an element and a compound?
What is the primary distinction between an element and a compound?
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Which of the following methods can best be used to separate a mixture of a solid and liquid?
Which of the following methods can best be used to separate a mixture of a solid and liquid?
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What happens to the average energy of particles as temperature increases?
What happens to the average energy of particles as temperature increases?
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How does relative atomic mass differ from nucleon number?
How does relative atomic mass differ from nucleon number?
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Which of the following statements about diffusion is accurate?
Which of the following statements about diffusion is accurate?
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Which statement about diffusion is correct?
Which statement about diffusion is correct?
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What effect does increased temperature have on the speed of gas particles?
What effect does increased temperature have on the speed of gas particles?
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Which of the following is NOT affected by the size of the particles during diffusion?
Which of the following is NOT affected by the size of the particles during diffusion?
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In which state of matter does diffusion occur the least quickly?
In which state of matter does diffusion occur the least quickly?
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What causes the pressure of a gas?
What causes the pressure of a gas?
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Which factor primarily influences the rate at which particles collide with the walls of their container?
Which factor primarily influences the rate at which particles collide with the walls of their container?
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Which of the following statements about particle movement is correct?
Which of the following statements about particle movement is correct?
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Who proposed the Nuclear Model of the atom?
Who proposed the Nuclear Model of the atom?
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What is unique about the electron cloud model proposed by Heisenberg and Schrodinger?
What is unique about the electron cloud model proposed by Heisenberg and Schrodinger?
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Which atomic theory describes electrons orbiting the nucleus like planets around the sun?
Which atomic theory describes electrons orbiting the nucleus like planets around the sun?
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What does the Wave Mechanical Model propose about electrons?
What does the Wave Mechanical Model propose about electrons?
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What did John Dalton contribute to atomic theory?
What did John Dalton contribute to atomic theory?
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How are chemical symbols for elements typically derived?
How are chemical symbols for elements typically derived?
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Which of the following is a correct elemental symbol for a pure element?
Which of the following is a correct elemental symbol for a pure element?
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In the context of atomic theories, which model focuses on the probability of finding an electron in a given area?
In the context of atomic theories, which model focuses on the probability of finding an electron in a given area?
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What is the relative atomic mass of oxygen?
What is the relative atomic mass of oxygen?
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What do isotopes of an element share in common?
What do isotopes of an element share in common?
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Which element has a relative atomic mass of 64?
Which element has a relative atomic mass of 64?
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What is the arrangement of electrons in a nitrogen atom with an atomic number of 7?
What is the arrangement of electrons in a nitrogen atom with an atomic number of 7?
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Which radioisotope is naturally occurring?
Which radioisotope is naturally occurring?
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What is the maximum number of electrons in the third shell of an atom?
What is the maximum number of electrons in the third shell of an atom?
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Which of the following is NOT a property of radioisotopes?
Which of the following is NOT a property of radioisotopes?
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What distinguishes a mass spectrometer from other analytical tools?
What distinguishes a mass spectrometer from other analytical tools?
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What does the Kinetic Model Theory state about particles in matter?
What does the Kinetic Model Theory state about particles in matter?
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How does temperature affect a substance's state at room temperature of 20 °C?
How does temperature affect a substance's state at room temperature of 20 °C?
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What is the principal difference between evaporation and boiling?
What is the principal difference between evaporation and boiling?
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What determines the volatility of a liquid?
What determines the volatility of a liquid?
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How does atmospheric pressure affect boiling point?
How does atmospheric pressure affect boiling point?
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Which of the following correctly describes a volatile liquid?
Which of the following correctly describes a volatile liquid?
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Which factor does NOT affect the rate of evaporation?
Which factor does NOT affect the rate of evaporation?
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At what condition does water boil at a temperature higher than 100 °C?
At what condition does water boil at a temperature higher than 100 °C?
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Study Notes
Learning Outcomes
- Three states of matter: solid, liquid, gas
- Changes of state: melting, freezing, vaporization, condensation, sublimation, deposition
- Atoms, molecules, and ions
- Separating and purifying substances
- Filtration, separating funnel, crystallization, distillation, paper chromatography
- Criteria of purity
- Elements and compounds
- Atomic theory
- Kinetic model and changes of state
- Diffusion
- Atomic structure and subatomic particles
- Proton number
- Nucleon number
- Isotopes
- Relative atomic mass
- Arrangement of electrons in atoms
States of Matter
- Matter is anything that has mass and takes up space
- Matter exists as a solid, liquid, gas, and plasma
- Solids have a definite shape and volume, high density, incompressible and low diffusivity
- Liquids have a defined volume but adapt to the shape of their container, high density, and incompressible
- Gases have no definite shape or volume but adapt to the shape and volume of their container, low density and compressible
States of Matter Properties
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Solid: fixed shape, fixed volume, high density, incompressible, low diffusivity
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Liquid: fixed volume, takes shape of container, high density, incompressible
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Gas: takes shape and volume of container, low density, compressible, widely spaced particles
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Plasma: fourth state of matter, electrically charged gas
Changes of State
- Melting point (m.p.): temperature at which a solid changes to a liquid
- Boiling point (b.p.): temperature at which a liquid changes to a gas
- Evaporation: change of liquid to gas at a temperature below the boiling point
- Sublimation: change of solid to gas without becoming a liquid
- Deposition: change of gas to solid without becoming a liquid
- Condensation: change of gas to liquid
Kinetic Model Theory
- All matter is made up of tiny particles
- All particles are in constant random motion
- The arrangement of particles is different for each state (solid, liquid, gas)
- The more often the particles collide with the walls of the container, the greater the pressure
Kinetic Model Theory (Continued)
- Particles in gases move very quickly and randomly
- Particles in liquids move more slowly than those in gases but faster than those in solids
- Particles in solids vibrate in fixed positions
Pure Substances vs. Mixtures
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Pure substance: single substance, invariant chemical composition, distinct properties
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Mixture: two or more pure substances, retain individual identities, separated by physical methods
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Homogeneous mixture: mixtures with uniform composition & properties throughout (solution)
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Heterogeneous mixtures: mixtures that are not uniform in their composition & properties
Separating Techniques
- Decantation: pouring off the liquid after a solid settles at the bottom
- Filtration: separates a solid from a liquid (insoluble)
- Centrifugation: isolates solid based on density difference
- Separating funnel: separates immiscible liquids based on density
- Evaporation: method to obtain a soluble solid from a solution by evaporating the liquid
- Crystallization: separates a soluble solid from a solution by cooling
Separating Techniques (Continued)
- Fractional distillation: separates miscible liquids based on differences in boiling points
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Chromatography: method of separating components of different solubility in a solvent
- Different substances move across the chromatography paper at different speeds based on their interactions with the solvent
- Paper chromatography: separation of components of a mixture using paper and a solvent
- Rf value: ratio of how far a material travels on the paper to the solvent front
Diffusion
- spreading of particles from a region of higher concentration to a region of lower concentration
Impurities Effects on Melting & Boiling Points
- Impurities in a substance lower its melting point and raise its boiling point
- The changes in melting and boiling points may spread over a range of temperatures
Phase Change Diagrams & Heating/Cooling Curves
- Graphical representations of physical states of a substance under varying temperature and pressure conditions
- Heating curves for pure substances show a constant temperature during phase changes (melting, boiling)
- Heating curves for mixtures show a range of temperature during phase changes
Water & Ice
- Salt lowers the freezing point of ice, speeding up the melting of ice.
Definitions
- Volatility: tendency of a substance to evaporate at normal temperatures
- Solvent: substance capable of dissolving other substances (usually a liquid)
- Solute: substance dissolved by the solvent
Classification of Matter (Elements & Compounds)
- Element: pure substance composed of only one type of atom, cannot be broken down into simpler substances
- Compound: pure substance composed of two or more different types of elements chemically bonded in a fixed ratio
Atomic Theory Development
- Various scientists like Democritus, Dalton, Thomson, Rutherford, Bohr and Schrödinger contributed to understanding the atom
Element Identification
- Symbols: elements are represented with a unique symbol(one or two letters)
Chemical Language
- Dalton proposed elements should have unique symbols
More Definitions
- Atom: basic unit of matter
- Molecule: group of two or more atoms joined together by chemical bonds
- Ion: atom or molecule with a net electric charge
Kinetic Model and Diffusion Properties
- Heavier particles move more slowly than lighter ones. Also bigger molecules diffuse slower than smaller ones
- Pressure of a gas is from collisions of particles with the container walls.
- Heat increases the average speed of particles
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