Notes, summaries, assignments, exams, and exercises for Chemistry for Secondary education

States of Matter

• Solid State: Attractive forces are greater than repulsive forces. They possess a defined shape and volume, are rigid, and cannot be compressed. Molecules are highly ordered.
• Liquid State: These do not have a proper form but maintain a specific volume, adapting to the shape of the container. Molecules are disordered, and forces of attraction and repulsion are balanced.
• Gaseous State: These have no defined form or volume, conforming to the shape of the container. Molecules are separated by repulsive forces and can be compressed easily. Component molecules move freely.

Changes in State

• Solid to Liquid: Fusion
• Liquid to Solid: Solidification
• Liquid to Gas: Vaporization
• Gas to Liquid: Liquefaction or Condensation
• Gas to Solid: Sublimation
• Solid

Atoms, Molecules, and Ions

Atoms: Electrically balanced particles consisting of one positively charged center called the nucleus, surrounded by a cloud of negatively charged particles called electrons, which exactly balance the nuclear charge.

Molecules: Electrically balanced particles with more than one positive center (nuclei). Molecules are sets of bonded atoms that act as a unit.

Ions: Atoms (or groups of atoms) with unbalanced charges.

The number of protons determines the number of electrons necessary to balance the atom's charge. Neutrons are the cementing material in the nucleus. The force between protons and neutrons is called the strong nuclear interaction. Number of protons = ATOMIC NUMBER of the atom (Z)

The atomic number is also given...

Fundamental Chemical Concepts

Diffusion is the movement of particles through a liquid or gas.

• Elements consist of only one type of atom.
• Compounds are substances that are chemically bonded.
• Mixtures are easily separated, unlike compounds.

Chemical Bonding and Atomic Structure

Covalent Bonding and Structures

A covalent bond is a shared pair of electrons.

Types of Covalent Structures

• Simple Molecular Substances: The atoms within a molecule are held together by very strong covalent bonds.
• Giant Covalent Structures: Similar to ionic structures, except that there are no charged ions. All the atoms are bonded to each other by strong covalent bonds.

Isotopes and Relative Atomic Mass

Isotopes are different atomic forms of the same element. They have the same number...

Factors Determining Changes of State

The changes in the state of a body are determined by several factors:

• The rise or drop in temperature.
• The rise or drop in pressure.
• The vapor pressure of a body.
• The state of cohesion or molecular aggregation.
• The chemical composition of the substance.

Defining Distillation

Distillation is a physical process of separating two or more liquids based on their boiling points.

Separating Complex Mixtures

A mixture of multiple substances (e.g., 10 substances) can often be separated effectively by chromatography.

Definitions of Phase Changes

• Fusion: The physical change from a solid state to a liquid state, typically achieved by increasing temperature.
• Solidification: The change from a liquid state to a solid state, typically

Kinetic Model of Gases: Microscopic Behavior

For centuries, scientists sought a model to explain the behavior of gases at the microscopic level. The simplest model assumes that a gas consists mainly of empty space occupied by small particles in constant, chaotic motion. This model is called the Corpuscular Kinetic Model.

Key Characteristics of Gases

• When heated, gas temperature increases.
• Gases exert pressure.
• Gases tend to fill the entire volume available.
• A larger volume may result in less pressure (at constant temperature).
• Higher volume and higher temperature are related.
• At higher temperatures, gases diffuse more rapidly.

The Kinetic Theory of Matter

Matter consists of very small particles that cannot be seen. These particles are in continuous,...

५. बोस्निया र हर्जगोभिना

बर्लिन सम्मेलन (१८७८) ले बाल्कन क्षेत्रमा अवस्थित दुई राज्यहरू बोस्निया र हर्जगोभिनाको जिम्मा हङ्गेरीलाई सुम्पेको थियो। अस्ट्रिया-हङ्गेरीलाई ती राज्यहरूको रेखदेख गर्ने अधिकार थियो तर उसले आफूमा गाभ्न पाउँदैनथ्यो। तर सन् १९०८ मा अस्ट्रिया-हङ्गेरीले बोस्निया...

Identifying Characteristic Properties of Pure Substances

Pure substances can be identified by their qualitative properties, such as odor, color, physical state (solid, liquid, gas), crystalline form and hardness.

Their quantitative properties include density, melting temperature, boiling temperature, solubility and electrical conductivity.

Melting Point

Ice melts at 0 °C. A pure substance melts at a determined temperature, and while it is melting its temperature remains constant. If the substance is not pure, its melting occurs over a range of temperatures and the melting point decreases as impurities are added.

Boiling Point

A pure substance boils at a determined temperature that remains constant during boiling. If the pressure increases, the boiling...

Chemical Compounds and Nomenclature

Metal Oxides: Formed by the reaction of a metal with oxygen. Formula: metal + oxygen. Name: rust in some cases, or the metal oxide name.

Nonmetal Oxides: Formed by the reaction of a nonmetal with oxygen. Formula: nonmetal + oxygen. Name: mono-, di-, tri-, tetra-, penta- oxide prefixes indicate the number of atoms.

Hydroxides: Compounds containing the metal cation bonded to the hydroxide anion (OH^-). Formula: metal (OH)_n. Name: metal hydroxide.

Oxoacids: Compounds of hydrogen, oxygen and a nonmetal. Formula: H_n(nonmetal)O_m. Naming: the -ic and -ous endings and the per- and hypo- prefixes indicate the oxygen content.

Hydracids: Binary compounds of hydrogen and a nonmetal. Formula: HnonM. Name: acid with the suffix...