Understanding Matter, Mass, Weight, and Energy Concepts
Understanding Matter, Mass, Weight, and Energy
All we can see and touch is matter. There are also material things we cannot see, like air.
We note that matter occupies a certain portion of space we call volume. In the case of air, this is not obvious, but the next experience will help us prove it.
Mass
Mass represents the coefficient of inertia of a body, i.e., the resistance the body opposes to changes in its state of motion or stillness.
Weight
Weight is the measure of the gravitational force acting
Read MoreKey Concepts in Chemistry: Atoms, Reactions, Acids
Periodic Trends
- Ionization Energy: Energy required to remove an electron.
- Atomic Radius: The total distance from an atom’s nucleus to the outermost orbital of an electron.
- Electron Affinity: Energy change associated with the addition of an electron.
- Electronegativity: Ability to attract an electron. Fluorine is the most electronegative element.
Electron Configuration
- Hund’s Rule: When there are different orbitals of the same energy, they first get occupied with a single electron.
- Pauli Exclusion Principle:
Atomic Structure and Quantum Theory Fundamentals
Z (Atomic Number) = Number of Protons = Number of Electrons.
A (Mass Number) = Protons + Neutrons.
Origins of Quantum Theory
Although the Rutherford model successfully explained the observed experimental evidence, it was inherently inconsistent. It was known that when an electric charge (q) moves with accelerated motion, it loses energy in the form of electromagnetic radiation. The electron in circular motion around the nucleus is subjected to centripetal acceleration; therefore, it must lose energy.
Read MoreChemical Reactions and Laws: Essential Concepts
Chemical Reactions and Fundamental Laws
Chemical Reaction: A process involving the combination of two or more initial substances, called reagents, resulting in new products. These products possess physical and chemical properties entirely distinct from the starting substances.
Key Laws Governing Chemical Reactions
Lavoisier’s Law (Law of Conservation of Mass): In any chemical reaction, the total mass of the reactants is equal to the total mass of the products. In essence, “In a chemical reaction,
Read MoreThermochemistry and Chemical Equilibrium
Work and Heat
Reversible processes are those in which the system and surroundings are in constant equilibrium; involves infinitesimal changes to some property:
- Slow heating
- Slow expansion
Irreversible processes are those in which the system and surroundings are not in equilibrium:
- Expansion against constant pressure
- Phase change at non-standard transition temperature
Internal Energy
For isothermal processes where ΔT = 0, ΔU = 0 and therefore q = -w.
At constant volume, ΔU = q.
Enthalpy
At constant pressure,
Read MoreChemical Processes in the Environment
Environmental Chemistry
Atmospheric Chemistry (Acid Rain, Smog)
In the air, there are a variety of chemicals. Often, these chemicals combine with each other through chemical reactions, creating new types of chemicals. This is called “atmospheric chemistry.” Earth’s atmosphere has different layers. The lowest layer is called the troposphere. We live in the troposphere. Some of the chemicals in the air come from pollution. Most of the gas in our atmosphere is nitrogen. Approximately 4/5 of air is nitrogen.
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