What is the law of conservation of energy?

Energy cannot be created or destroyed, only transformed.

What does a coefficient in a balanced chemical equation represent?

The number of molecules or formula units involved in the reaction.

Chemistry Fundamentals Cheat Sheet

This cheat sheet covers essential chemistry concepts including unit conversions, scientific notation, laws of conservation, states of matter, atomic structure, the periodic table, bonding, chemical reactions, and stoichiometry.

Core Principles

Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Conservation of Matter: Matter cannot be created or destroyed in a chemical reaction.
States of Matter: Transitions between solid, liquid, and gas occur with changes in temperature and pressure.
Atomic Structure: Atoms consist of protons, neutrons, and electrons, defining elements and their properties.
Periodic Table Trends: Properties like atomic radius and electronegativity follow predictable patterns across periods and down groups.
Bonding Types: Elements form ionic, polar covalent, or nonpolar covalent bonds based on electron sharing.
Chemical Reactions: Reactants transform into products, obeying laws of conservation and stoichiometry.
Stoichiometry: Predicts quantitative relationships between reactants and products in chemical reactions.

Action Steps

1. Balance chemical equations before solving stoichiometry problems.
2. Identify reactants and products to write correct chemical formulas.
3. Use conversion factors to change units (e.g., mm to km, L to mL).
4. Apply the octet rule to predict bonding and draw Lewis structures.
5. Determine bond type (ionic, polar covalent, nonpolar covalent) based on electronegativity differences.
6. Recognize signs of chemical change (e.g., gas production, color change, heat release).
7. Classify matter as element, compound, or mixture.
8. Use scientific notation for very large or very small numbers.

Formulas

Percentage Error = $|\frac{\text{Actual Value} - \text{Experimental Value}}{\text{Actual Value}}| \times 100$
Specific Gravity = $ \frac{\text{Density of Substance}}{\text{Density of Water}} $
$1 \text{ Cal} = 4.184 \text{ J}$
$1 \text{ cal} = 4.184 \text{ J}$
$1 \text{ J} = 0.239 \text{ cal}$
$1 \text{ J} = 0.239 \text{ Cal}$
Electron Configuration for Magnesium (Mg): $1s^2 2s^2 2p^6 3s^2$
Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a full outer shell of eight valence electrons.

Key Terms

Element: A pure substance consisting only of atoms that all have the same numbers of protons in their nuclei.
Compound: A substance formed when two or more chemical elements are chemically bonded together.
Mixture: A substance comprising two or more components not chemically bonded.
Specific Gravity: The ratio of the density of a substance to the density of a reference substance (usually water).
Percentage Error: The difference between an experimental value and the accepted value, expressed as a percentage of the accepted value.
Scientific Notation: A way of expressing numbers that are too large or too small to be conveniently written in decimal form.
Law of Conservation of Energy: Energy cannot be created or destroyed, only converted from one form to another.
Law of Conservation of Matter: Matter cannot be created or destroyed in a chemical reaction.
Isotopes: Atoms of the same element that have different numbers of neutrons.
Atomic Number: The number of protons in the nucleus of an atom.
Mass Number: The total number of protons and neutrons in an atom's nucleus.
Electronegativity: A measure of the tendency of an atom to attract a bonding pair of electrons.
Atomic Radius: One-half of the distance between the nuclei of two identical atoms bonded together.
Noble Gases: Elements in Group 8A of the periodic table, known for their inertness.
Alkali Metals: Elements in Group 1A of the periodic table, highly reactive metals.
Ionic Bond: A bond formed by the electrostatic attraction between oppositely charged ions.
Covalent Bond: A bond formed by the sharing of electrons between atoms.
Molecule: A group of two or more atoms held together by chemical bonds.
Chemical Reaction: A process that involves rearrangement of the molecular or ionic structure of a substance.
Reactant: A substance that takes part in and undergoes change during a reaction.
Product: A substance that is produced by a chemical reaction.
Mole: The SI unit for the amount of substance; contains Avogadro's number of particles.
Avogadro's Number: The number of constituent particles (usually atoms or molecules) that are contained in the amount of substance given by one mole; approximately $6.022 \times 10^{23}$ particles per mole.
Exothermic Reaction: A reaction that releases energy, usually in the form of heat.
Subscript: A number written below and to the right of a chemical symbol in a formula, indicating the number of atoms of that element in a molecule.
Coefficient: A number placed in front of a chemical symbol or formula, indicating the number of units or molecules.

Timeline

Ancient Greece: Philosophers like Democritus propose the idea of indivisible particles (atoms).
Early 19th Century: John Dalton develops atomic theory, proposing elements are made of atoms and compounds are combinations of atoms.
Late 19th Century: Discovery of the electron (J.J. Thomson) and the nucleus (Ernest Rutherford), leading to new atomic models.
Early 20th Century: Niels Bohr proposes a model where electrons orbit the nucleus in specific energy levels.
Mid-20th Century: Development of quantum mechanics provides a more accurate description of electron behavior (electron cloud model).
1913: Henry Moseley establishes atomic number as the basis for the periodic table's organization.
1916: Gilbert N. Lewis proposes the concept of the covalent bond and Lewis dot structures.

People

John Dalton: Developed atomic theory.
J.J. Thomson: Discovered the electron.
Ernest Rutherford: Discovered the atomic nucleus.
Niels Bohr: Proposed the Bohr model of the atom.
Henry Moseley: Established atomic number as the basis for the periodic table.
Gilbert N. Lewis: Developed the concept of the covalent bond and Lewis dot structures.

Quiz

What is the law of conservation of energy?: Energy cannot be created or destroyed, only transformed.
What is the primary difference between isotopes?: Number of neutrons
Which type of bond involves the sharing of electrons?: Covalent bond
What does a coefficient in a balanced chemical equation represent?: The number of molecules or formula units involved in the reaction.