Chemistry: Matter, Properties, and Chemical Changes
Chemistry: A Physical Science
Science is the knowledge obtained by observing natural events and conditions to discover facts and formulate laws or principles. Chemistry is the study of the composition, structure, and properties of matter, the processes that matter undergoes, and the energy changes that accompany these processes. A chemical is any substance with a definite composition.
Branches of Chemistry
- Organic Chemistry: The study of materials with carbon.
- Inorganic Chemistry: The study of non-organic
Properties and Extraction of Non-Ferrous Metals
Non-Ferrous Metals: Properties and Uses
There are also other non-ferrous metals.
1. Chrome
Chrome has a steely gray color, is very hard, and possesses great sharpness. It resists oxidation and corrosion very well. It is used as polished chrome for decorative objects, as hard chrome for the manufacture of stainless steels and tool steels.
- Density: 6.8 kg/dm³
- Melting point: 1900 °C
- Resistivity: 1.1 ohm ⋅ mm²/m
2. Nickel
Nickel has a bright silver color and can be polished very easily. It is magnetic
Read MoreFundamentals of Chemistry: Atoms, Reactions, and Laws
**1. The Atom**
- Structure:
- Protons (positive charge) in the nucleus.
- Neutrons (neutral) in the nucleus.
- Electrons (negative charge) in orbitals around the nucleus.
- Atomic Number (Z): Number of protons in an atom.
- Mass Number (A): Total number of protons and neutrons.
- Isotopes: Atoms of the same element with different numbers of neutrons.
**2. The Periodic Table**
- Groups (columns): Elements in the same group have similar properties.
- Periods (rows): Properties change across a period.
- Key Groups:
- Group 1: Alkali
Redox Reactions: Understanding Electrode Potentials
Measurement of Energy in Redox Processes
The energy associated with a single redox process cannot be measured; only two processes together are measured. Taking the energy of the hydrogen electrode as a reference = 0 volts.
Electrode Potentials
A cell consisting of a type X electrode (cathode) versus a hydrogen electrode (anode).
The energy of redox processes taking place in solution is measured in volts, and it depends on the concentration.
Potentials given in the tables are measured at 1M of cations
Read MoreAtomic Structure and the Periodic Table: Properties and Trends
Limitations of the Bohr Model
The Bohr model could not explain why the orbits were quantized, nor why some properties of the elements are repeated periodically. Experimental results also did not fit this model:
- By increasing the resolution of the spectrograph, it was shown that some lines of the spectrum were in fact two.
- When making the spectrum while the substance is subjected to an intense magnetic field, it was observed that some spectral lines unfold into several.
Quantum Mechanical Model
The basic
Read MoreElectrochemistry and Cement: Principles and Applications
Electrochemistry
What is EMF, and What is its Significance in Electrochemistry?
- EMF (Electromotive Force) is the potential difference between two electrodes when no current flows. It drives the redox reaction in an electrochemical cell.
- Significance:
- Determines the spontaneity of a reaction (\(\Delta G^\circ = -nFE^\circ_{cell}\)).
- Measures the energy available for work.
- Helps calculate thermodynamic parameters like the equilibrium constant and Gibbs free energy.
Working Principle and Reactions in a Glass