Core Chemistry Concepts: Matter, Atoms, and Reactions
States of Aggregation
Matter exists in different states based on the intensity of forces between particles:
- Solid: Forces of attraction are very intense. Solids are rigid, cannot flow, maintain their own shape and volume, and are incompressible.
- Liquid: Forces are less intense than in the solid state. Liquids can flow, do not have their own shape (taking the shape of the container), maintain their own volume, and are nearly incompressible (often treated as incompressible, though slight compressibility
Chemical Principles: Thermo, Kinetics, Eq
Work
- Isobaric Process: At constant pressure (P = cte)
W1→2 = -PΔV - Isothermal Process: At constant temperature (T = constant)
W1→2 = -nRT ln(P1/P2) - Isochoric Process: At constant volume (V = constant)
W1→2 = 0
Heat
- Specific Heat: c = dQ / (mΔT)
Q = c · m · ΔT
If ΔT > 0, heat is absorbed.
If ΔT < 0, heat is ceded (released). - Latent Heat of Change of State (L): At constant temperature
From solid to liquid: Qf = m · Lf
From liquid to gas: Qv = m · Lv
First Law of Thermodynamics
ΔU = Q + W
Calculating
Read MoreStates of Matter and Phase Changes
Solids
In the solid state, the particles are touching, and the only motion allowed to them is vibration. The particles may be arranged regularly (in which case, the solid is crystalline), or at random (giving waxy solids like candles or some forms of polyethylene, for example).
The particles are held in the solid by forces which depend on the actual substance – ionic bonds, covalent bonds, metallic bonds, hydrogen bonds, or van der Waals attractions.
Liquids
In a liquid, the particles are mainly touching,
Read MoreAtomic Structure, Isotopes, and Mass Calculation
Sub-atomic Particles & Atomic Structure
- Protons, neutrons, and electrons are the sub-atomic particles of an atom.
- Scientists developed notations to easily identify the numbers and arrangement of these particles within the atom.
Atomic number (Z): The number of protons in the nucleus.
Mass number (A): The total number of protons and neutrons in an atom.
A = Z + N (where N is the number of neutrons)
Finding the Number of Neutrons
To find the number of neutrons, subtract the atomic number (Z) from the
Read MoreFundamentals of Chemical Bonding and Compounds
Chemical Bonds
Covalent Bond Types
A covalent bond takes place between atoms that share pairs of electrons. The type depends on the electronegativity difference (ΔEN) between the atoms:
- Nonpolar covalent: Occurs between atoms sharing electron pairs with an electronegativity difference of zero (ΔEN = 0).
- Polar covalent: Occurs between atoms sharing electron pairs with an electronegativity difference greater than 0 but less than 1.7 (0 < ΔEN < 1.7).
- Coordinate covalent bond: In this bond, one
Fuel Properties, Coal Analysis, and Corrosion Science
Fuel Definition and Types
A fuel is defined as any substance that can provide heat and produce energy when it is burned. The energy released is generally in the form of chemical energy or heat energy.
Examples of fuel:
- Methanol
- Gasoline
- Diesel
- Natural gas
Types of fuel:
- Solid fuel
- Liquid fuel
- Biofuel
- Fossil fuel
Characteristics of a Good Fuel
A good fuel has the following characteristics:
- Availability: It should be readily available.
- Cost: It should be inexpensive.
- Combustion: It should burn easily in air at a