Understanding Electric Charges and Material Conductivity
Understanding Electric Charges
Matter contains two types of electric charges of opposite signs: positive and negative. Usually, bodies are electrically neutral. However, through certain physical processes, they can gain or lose electric charges, thus becoming electrically charged. These processes include:
- Charging by Friction
- Charging by Induction
- Charging by Contact
Charging by Friction
In everyday life, electrical phenomena often occur through friction. You can observe that bodies with like charges
Read MoreEssential Physical and Chemical Unit Operations
Physical Unit Operations
Distillation
An operation to separate, by vaporization and recondensation, the different components of a liquid or liquefied mixture. This process utilizes the varying boiling points of each substance to be separated.
Filtration
A separation technique or process unit operation where a mixture of solids and fluids (gas or liquid) is passed through a porous filter medium. This medium, often part of a device called a filter, retains most of the solid components of the mixture.
Sieving
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Understanding Materials, Atoms, and Chemical Processes
Material Classification
Materials are classified according to their source (natural materials, manufactured materials, or newly created) or according to their properties (metals and metal alloys, polymers, ceramics).
Manufacturing Processes
Manufacturing involves materials that have undergone a change or were obtained from a chemical process. Some materials are transformed without altering their chemical composition, while others are newly created.
Natural Materials
Natural materials are obtained from
Read MorePharmaceutical Compounds & Analytical Chemistry Essentials
Volumetric Analysis Fundamentals
Volumetric analysis is a method of quantitative chemical analysis where the amounts of substances are determined by measuring the volume they occupy in different proportions.
Types of Volumetric Methods
Volumetric methods are classified into types based on the reactions involved:
- Neutralization Titration
- Non-aqueous Titration
- Redox Titration
- Complexometric Titration
- Precipitation Titration
Neutralization Titration
Also known as acid-base titration in the aqueous phase, this
Read MoreOrganic Chemistry Reactions: Oxidation & Alcohol Transformations
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Question 1
Which one of the following statements does not describe an oxidation?
Correct Answer: Addition of a hydride ion
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Question 2
Which sequence shows the correct ordering with regard to an increase in the oxidation state for the oxidation of methanol?
Correct Answer: Methanol < Formaldehyde < Formic Acid < Carbon Dioxide
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Question 3
Which is the correct formula for sodium dichromate?
Correct Answer: Na2Cr2O7
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Question 4
Oxidations with chromic acid can easily be monitored since the oxidized
Atomic Models, Quantum Theory, and the Periodic Table
Thomson Model of the Atom
In the Thomson model, electrons (e-) are embedded in a sphere of uniform positive charge, like plums in a pudding. There is no distinct nucleus.
Rutherford’s Nuclear Model
The Rutherford model proposes a nucleus that is very small in comparison with the volume of the atom. This nucleus contains almost the entire mass of the atom and all of its positive charge. Electrons form a “crust” (electron cloud) spinning around the nucleus and are relatively far from it.