Notes, abstracts, papers, exams and problems of Chemistry

Chemical Bonding in Dental Materials

Primary Bonds

Factors Influencing Material Properties:

1. Type of bond between atoms and molecules
2. Inter-atomic distance
3. Atomic packing

Matter: Any substance that has mass and occupies space.

Atom: The fundamental unit of matter, consisting of a central nucleus (protons and neutrons) surrounded by electrons.

Types of Primary Bonds:

• Ionic Bond: Attraction between positive and negative ions. Characteristics: Strong, heat resistant, insulator, insoluble in organic solvents, basic bond in ceramics.
• Covalent Bond: Sharing of electrons between two atoms. Characteristics: Strong, insulator, water insoluble, basic bond in polymers.
• Metallic Bond: Attraction between positive atomic cores and free electrons. Characteristics: High

Temperature Conversions

• Celsius to Fahrenheit: F = (9/5) * C + 32
• Celsius to Kelvin: K = C + 273

Atomic Structure

• Atomic Mass: Protons + Neutrons (upper left symbol)
• Atomic Number: Protons (bottom left symbol)

Quantum Mechanics

• Planck's Constant (h): 6.6260755 x 10^-34 J*s
• Energy of a Photon: E = hv or E = hc / wavelength

Electronic Transitions

• Absorption: When energy is absorbed by an atom, an electron is excited to a higher energy level or orbital.
• Emission: When an electron relaxes from a higher energy orbital to a lower one, it emits a photon.

Filling Orbitals

s = 2, p = 6, d = 10, f = 14

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f

Periodic Trends

• Atomic Radius: Increases down a group and decreases across a row.
• Ionization Energy: Amount of energy

Production

Vocabulary: Dimensions

• Dimension: Big/Small
• Height: High/Low
• Depth: Deep/Shallow
• Width: Wide/Narrow
• Length: Long/Short
• Strength: Strong/Weak
• Thickness: Thick/Thin

Production 1

Improved quality control. Paper is an industrial process. It is the basic raw material. Increased productivity levels. The large store (for) finished product. Large factories use assembly lines. The company moved into large-scale manufacturing. The manufacturing (is the responsibility) of the production manager.

Complete the Sentences:

• Known as a batch.
• Is to assemble.
• Inputs to outputs.
• Is known as purchasing.
• Is called a component.
• Is to optimize.

Text:

We are making good progress with the new factory site layout: fixtures, equipment, machinery, workshops, etc. The present... Continue reading "Vocabulary for Manufacturing, Materials, and Energy" »

States of Matter

DIBUJO: 1 Liquid 2 Boiling point 3 Evaporating 4 Sublimation 5 Condensation 6 Melting 7 Solidification 8 Reverse sublimation

Evaporating

: It's not necessary to vaporize at 100°C

Boiling

: It's when a substance transforms to the gas state at a temperature of 100°C or higher

Graph

: 1-First, it's a solid substance 2 then the temperature increases 3 the solid substance melts and starts being a liquid substance 4 the temperature increases 5 the liquid substance vaporizes and starts being a gaseous substance 6 the temperature increases

Verify Pure Substance

: We know that a substance is pure because it has specific properties.

Sand+water

: Sedimentation - the sand stays at the bottom of the container and the water can be separated from... Continue reading "Understanding States of Matter and Separation Techniques" »

Chapter 1 : Matter and change

Branches of chemistry

Organic Chemistry – the study of most carbon-containing compounds.

Inorganic Chemistry – the study of most non-carbon-containing compounds.

Physical Chemistry – the study of the properties and changes of matter and their relation to energy.

Biochemistry – the study of substances and processes occurring in living things.

Analytical Chemistry – the identification of the components and composition of materials.

Theoretical chemistry – the use of mathematics and computers to understand the principles behind observed chemical behaviour and to design and predict the properties of new compounds.

Matter

Atom – the smallest unit of an element that maintains the chemical identity of that element.

Mixture

A mixture is a physical blend of two or more components.

Heterogeneous mixture

A mixture in which the composition is not uniform throughout is a heterogeneous mixture.

Homogeneous mixture

A homogeneous mixture is a mixture in which the composition is uniform throughout. Another name of homogeneous mixture is a solution.

Phase

The term phase is used to describe any part of a sample with a uniform composition and properties.

Filtration

The process that separates a solid from the liquid in a heterogeneous mixture is called filtration.

Distillation

One way to separate water from the other components in tap water is through a process called distillation.

Properties of Matter

Mass

The matter of an object is a measure of the amount of matter the object... Continue reading "Understanding Mixtures, Phases, and Chemical Reactions" »

Rutherford Experiment

The results of the gold foil experiment led to the discovery of a very densely packed bundle of matter with a positive electric charge. Rutherford called this positive bundle of matter the nucleus. He was trying to figure something else out and accidentally discovered this. As much of a discovery as the gold foil experiment was, it wasn’t discovered intentionally.

Atomic Number

Consists of the number of electrons or protons.

Mass Number

Consists of the protons added to the neutrons.

Nonpolar Covalent Bond

A covalent bond in which the bonding electrons are shared equally by the bonded atoms. Example: H-H

Polar Covalent Bond

A covalent bond in which the bonded atoms have an unequal attraction for the shared electrons. Example:... Continue reading "Introduction to Atomic Structure and Chemical Bonding" »

From Dalton to the Electron

The simple model set by Dalton needed updating. In 1894, Crookes discovered that cathode rays were produced just by applying a very high voltage between two electrodes. He observed that he could get a shadow, so his conclusion was that "some particles exit from the metal plate placed in the cathode." As those particles were attracted by the positive electrode, the so-called cathode rays had to have a negative charge. Thomson (1897) interpreted the experiment as showing that cathode rays were a stream of electrons. Atoms, as introduced by Dalton, were not indivisible. Since electrons were issued from a metal, atoms were made of electrons (negative charge) and something else with a positive charge because matter is... Continue reading "Atomic Structure: From Dalton to Rutherford" »