Chem Midterm 1

Matter

Anything that has mass and occupies space.

Energy

The capacity to do work or produce heat.

Element

A pure substance made of one type of atom; cannot be broken down chemically.

Atom

The smallest unit of an element that retains its properties.

Chemical Bond

The force that holds atoms together in compounds.

John Dalton

Proposed the first modern atomic theory; matter is composed of indivisible atoms.

J.J. Thomson

Discovered the electron via the cathode ray experiment.

Robert A. Millikan

Measured electron charge with the oil drop experiment.

Ernest Rutherford

Discovered the nucleus with the gold foil experiment.

Gold Foil Experiment

Showed that atoms have a small, dense, positively charged nucleus.

James Chadwick

Discovered the neutron.

Proton

Positively charged subatomic particle in the nucleus.

Neutron

Neutral particle in the nucleus, adds mass.

Electron

Negatively charged particle in electron clouds.

Isotope

Atoms of the same element with different neutron counts.

Ion

Atom or group with net charge from electron gain/loss.

Cation

Positively charged ion.

Anion

Negatively charged ion.

Mass Number

Total number of protons + neutrons in an atom.

Carbon-12

Stable isotope of carbon (6 protons, 6 neutrons), atomic mass standard.

Hydrogen (H)

Z=1, Atomic Weight=1.01; lightest element, highly reactive.

Helium (He)

Z=2, 4.00; inert noble gas, used in balloons, cryogenics.

Boron (B)

Z=5, 10.81; metalloid, used in glass/detergents.

Carbon (C)

Z=6, 12.01; backbone of organic life.

Nitrogen (N)

Z=7, 14.01; makes up 78% of air, essential for proteins/DNA.

Oxygen (O)

Z=8, 16.00; vital for respiration and combustion.

Fluorine (F)

Z=9, 19.00; most reactive halogen, used in toothpaste.

Neon (Ne)

Z=10, 20.18; inert gas, used in lighting.

Sodium (Na)

Z=11, 22.99; alkali metal, in table salt.

Phosphorus (P)

Z=15, 30.97; essential in DNA, ATP, fertilizers.

Sulfur (S)

Z=16, 32.07; used in sulfuric acid and rubber.

Chlorine (Cl)

Z=17, 35.45; halogen, in bleach and NaCl.

Argon (Ar)

Z=18, 39.95; inert noble gas, used in welding/lighting.

Potassium (K)

Z=19, 39.10; alkali metal, vital for nerve function.

Titanium (Ti)

Z=22, 47.87; strong, light metal for aerospace/implants.

Iron (Fe)

Z=26, 55.85; major component of steel.

Copper (Cu)

Z=29, 63.55; conductive, used in wiring.

Zinc (Zn)

Z=30, 65.38; used in galvanization, alloys.

Bromine (Br)

Z=35, 79.90; only liquid halogen, flame retardants.

Krypton (Kr)

Z=36, 83.80; noble gas, used in lighting.

Silver (Ag)

Z=47, 107.87; precious, conductive metal.

Iodine (I)

Z=53, 126.90; halogen, needed for thyroid.

Xenon (Xe)

Z=54, 131.29; noble gas, anesthesia, lamps.

Tungsten (W)

Z=74, 183.84; highest melting point, filaments.

Gold (Au)

Z=79, 196.97; precious metal, used in jewelry/electronics.

Mercury (Hg)

Z=80, 200.59; liquid metal, toxic.

Radon (Rn)

Z=86, 222.00; radioactive noble gas from uranium decay.

Homogeneous Mixture

Mixture uniform throughout (e.g., saltwater).

Heterogeneous Mixture

Mixture with non-uniform composition (e.g., salad).

Solution

Homogeneous mixture at molecular level.

Physical Property

Observed without changing substance identity (e.g., melting point).

Chemical Property

Describes chemical reactivity (e.g., flammability).

Extensive Property

Depends on amount of matter (mass, volume).

Intensive Property

Independent of amount (density, boiling point).

Reactant

Starting material in a reaction.

Product

Substance formed by a reaction.

Mass

Measure of matter in an object.

Law of Conservation of Mass

Mass is neither created nor destroyed in reactions.

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed.

Law of Definite Proportions

A compound has elements in fixed mass ratios.

Law of Multiple Proportions

Elements form compounds in small whole-number ratios.

Scientific Process

Systematic method of gaining knowledge.

Hypothesis

A testable prediction.

Observation

Data gathered via senses or instruments.

Experiment

Controlled test of a hypothesis.

Scientific Theory

Well-supported explanation of phenomena.

Scientific Law

Concise description of natural relationships.

SI Units

International metric system for science (e.g., m, kg, s, mol).

Tera- (T)

Metric prefix, 10¹².

Giga- (G)

Metric prefix, 10⁹.

Mega- (M)

Metric prefix, 10⁶.

Kilo- (k)

Metric prefix, 10³.

Deci- (d)

Metric prefix, 10⁻¹.

Centi- (c)

Metric prefix, 10⁻².

Milli- (m)

Metric prefix, 10⁻³.

Micro- (µ)

Metric prefix, 10⁻⁶.

Nano- (n)

Metric prefix, 10⁻⁹.

Pico- (p)

Metric prefix, 10⁻¹².

Femto- (f)

Metric prefix, 10⁻¹⁵.

Atto- (a)

Metric prefix, 10⁻¹⁸.

Qualitative Data

Descriptive, non-numeric info.

Quantitative Data

Numerical measurements.

Accurate Measurement

Closeness to true value.

Precise Measurement

Consistency of repeated results.

Sig Fig Rules (Multiplication/Division)

Result has same sig figs as the fewest in calculation.

Sig Fig Rules (Addition/Subtraction)

Result has same decimal places as least precise number.

Dimensional Analysis

Problem-solving using unit conversions.