Elements and Chemical Symbols

This section focuses on the characteristics of elements and how they are represented using chemical symbols. It explains that elements consist of atoms with the same atomic number and that there are approximately 100 different elements.

Example: Some common elements include copper, aluminium, iron, oxygen, and nitrogen.

The page introduces the concept of mass number and atomic number, explaining their significance in identifying elements. It also describes how chemical symbols are used to represent atoms of elements.

Definition: The mass number is the total number of protons and neutrons in an atom, while the atomic number represents the number of protons.

The information is presented using a visual representation of sodium $Na$ as an example, showing how the mass number, atomic number, and number of neutrons are related.

Isotopes and Relative Atomic Mass

This page delves into the concept of isotopes and introduces the calculation of relative atomic mass. Isotopes are defined as different forms of the same element with the same number of protons but a different number of neutrons.

Example: Carbon-12 and Carbon-13 are isotopes of carbon, differing in their number of neutrons.

The page explains the concept of relative atomic mass, which is an average mass that takes into account the different masses and abundances of all isotopes of an element.

Vocabulary: Relative atomic mass $Ar$ is calculated using the formula: Ar = sum of $isotope abundance × mass number$ / sum of abundances of all isotopes.

An example question is provided to illustrate how to calculate the relative atomic mass of carbon using its isotopes and their abundances.

Compounds and Chemical Bonding

This section explores the nature of compounds and how they differ from elements. Compounds are defined as substances formed from two or more elements chemically combined in fixed proportions.

Highlight: The properties of a compound are entirely different from those of the original elements.

The page distinguishes between compounds formed from metals and non-metals $ionic compounds$ and those formed from non-metals only $molecular compounds$. It explains the electron transfer and sharing processes involved in forming these compounds.

Example: Examples of molecular compounds include hydrogen chloride, carbon monoxide, and water.

The use of chemical formulae to represent compounds is introduced, with examples such as CO₂ for carbon dioxide and H₂SO₄ for sulfuric acid.

Mixtures and Separation Techniques

This page focuses on mixtures and various methods used to separate them. It explains that mixtures consist of two or more elements or compounds that are not chemically combined, making them easier to separate than compounds.

Definition: A mixture is a combination of two or more substances that are not chemically bonded and can be separated by physical means.

The page lists several separation techniques: • Filtration • Crystallization • Simple distillation • Fractional distillation • Chromatography

Example: Air is described as a mixture of gases, including nitrogen, oxygen, carbon dioxide, and argon.

The chromatography process is explained in detail, providing step-by-step instructions on how to perform this separation technique.

Filtration and Evaporation

This section provides detailed explanations of two separation techniques: filtration and evaporation. Filtration is described as a method used to separate an insoluble solid from a liquid.

Highlight: Filtration can also be used for purification, such as removing solid impurities from a liquid.

The page outlines the steps involved in the filtration process, explaining how the liquid passes through the filter paper while solid particles are caught.

Evaporation is introduced as a method to separate a soluble salt from a solution. The process is described step-by-step, emphasizing the gradual heating of the solution until only dry crystals remain.

Crystallization and Simple Distillation

This page covers two more separation techniques: crystallization and simple distillation. The crystallization process is explained in detail, describing how to obtain crystals from a solution by controlled evaporation and cooling.

Vocabulary: Crystallization is the process of forming solid crystals from a solution or vapor.

The simple distillation process is then introduced, explaining its use in separating a liquid from a solution. The page describes the setup of a distillation apparatus and the principles behind the separation.

Example: Simple distillation can be used to purify seawater, separating pure water from salt and other dissolved substances.

A diagram illustrating the simple distillation apparatus is provided, showing the key components such as the thermometer, condenser, and collection flask.

Fractional Distillation

The final page introduces fractional distillation, a more advanced separation technique used for separating liquids with different boiling points. The process is explained step-by-step, highlighting the use of a fractionating column.

Definition: Fractional distillation is a separation technique used to separate a mixture of liquids with different boiling points.

The page describes how the mixture is heated, and the liquid with the lowest boiling point evaporates first. It explains that the temperature at the top of the column indicates which liquid is being separated at that point.

Highlight: Liquids with higher boiling points will only partially ascend the fractionating column, allowing for effective separation of multiple components.

This technique is particularly useful for separating complex mixtures of liquids with similar boiling points, such as those found in crude oil refining or alcohol production.

Fractional Distillation

This final section introduces fractional distillation.

Definition: Fractional distillation separates liquids with different boiling points using a fractionating column.

Highlight: The process relies on temperature gradients within the column.

Example: Different components separate based on their unique boiling points.

Atomic Structure and Subatomic Particles

This page introduces the fundamental concepts of atomic structure and subatomic particles. It explains that all substances are composed of atoms, which contain three subatomic particles: protons, neutrons, and electrons. The page provides details on the relative mass and charge of these particles, as well as their locations within the atom.

Definition: An atom is the smallest unit of matter that retains the properties of an element.

The nucleus of an atom is described as having a radius of about 1x10^-14 m, containing protons and neutrons, and carrying a positive charge. It also concentrates most of the atom's mass.

Highlight: The electrons move around the nucleus in shells, are negatively charged, and have virtually no mass.

The page emphasizes that while electrons are tiny, they cover a significant amount of space around the nucleus, giving atoms a radius of about 0.1 nm.