fundamentals- gen chem I

Pressure of an ideal gas

Always greater than the pressure of a real gas.

Volume of a real gas

Greater than the volume of an ideal gas.

law of conservation of mass

Matter is conserved; it can't be created or destroyed, only rearranged or changed in form.

law of conservation of energy

Energy is conserved; it cannot be created or destroyed, only transformed between forms.

macroscopic view

What we see (e.g., blue flame).

molecular/chemical equation view

Symbols and equations.

particulate view

Atoms/particles interacting.

extensive properties

Properties that change with the amount of matter. Examples: mass, volume.

intensive properties

Properties that do not depend on the amount of matter. Examples: density, temperature, viscosity, pressure.

evaporation

Liquid → Gas.

condensation

Gas → Liquid.

freezing

Liquid → Solid.

melting

Solid → Liquid.

sublimation

Solid → Gas.

deposition

Gas → Solid.

physical change

A change in state/form without forming a new substance (e.g., melting ice).

chemical change

Atoms are rearranged; new substances are formed.

common signs of a chemical change

Gas production (bubbles/fizzing), color change, light emission, heat change, rusting, precipitation, odor change.

pure substance

A substance made of only one kind of element or compound, uniform throughout.

elements

Examples: Carbon, Oxygen, Chlorine, Gold, Silver.

compounds

Examples: Water (H₂O), Salt (NaCl), Ammonia (NH₃).

mixture

Two or more substances combined physically, not chemically.

homogeneous mixture

Looks uniform throughout (solution).

heterogeneous mixture

Not uniform, can often see different parts.

suspension

A heterogeneous mixture where particles settle out over time and can be filtered (e.g., muddy water).

colloid

A heterogeneous mixture with medium-sized particles that scatter light, don't settle quickly, and can't be filtered (e.g., milk, fog).

solution

Homogeneous mixture with particles <1 nm (atoms, ions, molecules), single phase, never settle, cannot be filtered (e.g., saltwater, Kool-Aid, soda).

alloy

A homogeneous mixture of two or more elements, at least one metal, with metallic properties (e.g., steel, brass).

Macroscopic properties of a solid

Holds shape, rigid.

Macroscopic properties of a liquid

Does not hold shape, flows but does not fill the container.

Macroscopic properties of a gas

Does not hold shape, fills container completely.

Properties used to arrange elements in the periodic table

Atomic mass, electronegativity, reactivity/volatility, atomic radii, relative abundance, melting points.

Smallest particle of an element that retains its chemical identity

An atom.

Dalton's Atomic Theory

1. Elements are made of indivisible atoms (Democritus). 2. Atoms of one element are identical but differ from other elements. 3. Atoms can mix or chemically combine in simple whole-number ratios to form compounds (Proust). 4. Atoms are neither created nor destroyed in chemical reactions (Lavoisier). 5. A given compound always has the same relative numbers and kinds of atoms (Proust).

Law of combining volumes

At constant T and P, the volume ratio of gases in a chemical reaction is a ratio of simple integers.

Example of combining volumes of H₂ and O₂

2 volumes of H₂ react with 1 volume of O₂ to form 2 volumes of H₂O vapor.

Example of combining volumes of N₂ and H₂

1 volume of N₂ reacts with 3 volumes of H₂ to form 2 volumes of NH₃.

Avogadro's hypothesis

Equal volumes of different gases at the same temperature and pressure contain equal numbers of molecules.

Approximation of Avogadro's hypothesis

Different gases interact differently; real gases deviate.

Faraday's proposal about atomic structure

That it is related to electricity; matter has negative and positive charges that interact.

Who first identified the two types of charge

Benjamin Franklin — positive and negative.

Three subatomic particles and their properties

Proton: +1 charge, mass ≈ 1. Neutron: 0 charge, mass ≈ 1. Electron: −1 charge, mass ≈ 1/1836 of a proton.

Location of protons, neutrons, and electrons

Protons and neutrons in the nucleus; electrons in the electron cloud (most of atom's volume).

Size of the nucleus compared to the atom

Nucleus = ~1/10,000 the size of atom. (Analogy: stadium vs BB pellet).

Atomic number (Z)

The number of protons (nuclear charge).

Nuclear charge of C, Ca, U

C = +6, Ca = +20, U = +92.

Description of compounds

By molecular formulas with atoms in fixed, whole-number ratios.

Defining feature of a neutral atom

Number of protons = number of electrons.

solid

liquid

gas

pure element