CBSE Class 12 Chemistry: Key Concepts, Theories, & More

Ever wonder what is the difference between classes in school? Do you find yourself struggling with concepts that don't seem to be relevant in the real world? Wonder no more, as we have compiled a comprehensive guide on what you need to know about the 12th chemistry guide! Find out key concepts, theories, & more about chemistry classes & the CCSE Board exam. Don't forget to stay tuned until the end, where we'll tell you everything you need to know about the exam itself.

Key Concepts In Chemistry

As with any other science subject, chemistry is often taught using a combination of lessons and experiments. But what exactly do you need to know about chemistry that isn't immediately obvious? Let's take a look:

Atomic Theory

The standard model of chemical element division is called the "Atomic Theory." It states that chemical elements are made up of atoms, which are indivisible. This means that you cannot have half of an atom, but instead, you have to have all of it. While this may seem straightforward enough, it is actually a very complex idea to fully understand. The four basic postulates of the atomic theory are:

• All matter is composed of atoms

• Atoms are indivisible

• Atoms combine to form molecules

• Molecules can combine to form compounds

These postulates provide a useful framework for understanding chemical behavior. You can think of them as chemical laws. Consider the water molecule, for example. Two hydrogens and one oxygen combine to form H2O, or water. According to the theory, matter cannot be divided into smaller pieces, so you cannot separate the hydrogens or the oxygens from the water molecule. You have to have the whole thing!

Redox

In chemistry, a reagent is a chemical that can be used to change another substance. For example, iron(III) chloride is a common oxidizing agent because it can be used to oxidize various substances. When you use it, you are actually changing the oxidation state of the element you are working with. Elements with an odd number of electrons are more reactive and have an increased tendency to lose electrons. If an element gains enough electrons, it will become a positively charged ion – a cation. These cations are usually very unstable and will either decay or combine with other cations to form substances with different properties.

Law Of Conservation Of Mass

In chemistry, the law of conservation of mass simply says that the total amount of matter is conserved. This means that if you start with one gram of matter and end up with half a gram of matter, then the matter has not been created or destroyed. It has just changed its form. The law of conservation of mass applies to all matter, whether it is found in a living thing or an inorganic substance. You can't break it by studying or doing experiments in school, but you will learn about it in science classes. It is a fundamental law of nature.

Types Of Chemical Reactions

Just as there are many different elements and compounds, there are many different ways in which they can react. The four basic types of chemical reactions are:

• Reduction

• Oxidation

• Combustion

• Decomposition

In general, reduction is a process in which one or more substances lose electrons. When this happens, they become less acidic, more basic, or both. Redox is the study of these electron changes, and it is often used in science experiments. A substance that undergoes a reduction reaction becomes a "reductant" while a substance that undergoes an oxidation reaction becomes an "oxidant."

Combustion is the process in which substances break down into simpler compounds or elements. When matter is combusted, it usually loses its electrons and becomes a different element. For example, wood is mostly carbon and hydrogen, and when these elements are burned, they produce a lot of heat and various gasses. These gasses are what make up the familiar smells of a burning organic substance. The important thing to note about combustion is that it usually emits lots of toxic gases as well. In high temperatures, almost all organic materials undergo some type of decomposition, which is why most living organisms avoid heat.

Significant Figures In Chemistry

Just as there are many different elements in chemistry, there are many different ways of expressing quantities in science. The most basic form of expressing quantity is using numbers to denote a specific integer. For example, 24 is the same as 2 million. But these numbers are only used when talking about the exact value (to the hundredth decimal place) of a large amount of money or property. Otherwise, you use units, which are shorter versions of the words for the exact same things. There are 12 significant figures in chemistry. They are:

• 1 trillion

• 1 billion

• 100 million

• 10 million

• 1 million

• 100,000

• 10,000

• 1,000

• 100

• 10

A trillion (1,000,000,000) is a thousand (1,000) million. It is the same as a million million. A billion (1,000,000,000) is a million million, and it is the same as a trillion (1,000,000,000). Ten million (1,000,000,000) is the next bigger number, and so on.

Element Symbolism

In chemistry, certain elements have acquired special significance. These symbols are used in science papers to indicate the presence of particular elements. The most common of these symbols are:

• H: Hydrogen

• He: Helium

• Li: Lithium

• Mg: Magnesium

• Na: Sodium

• Ne: Neon

• O: Oxygen

The reason Hydrogen and Helium are significant is that most organic compounds contain them. They are both very small and light, so they are often used to signify the presence of a small, volatile element. Lithium and Magnesium are both alkali metals (they share the same row in the periodic table), and they both have unique properties that make them easy to recognize when they are present in a compound. Sodium and Neon also share similar physical properties. All of these elements are very reactive and can occur in numerous oxidation states. When present in an organic compound or a living organism, they can all play a significant role in chemical reactions.

Molecular Theory

The most important idea to understand about chemistry is that of molecules. This is a theory that states that all atoms in a compound are bound together by strong, electromagnetic forces. This means that chemical compounds can be considered to be composed of many little molecules bound together. A compound that follows the laws of quantum mechanics is said to be "quantum-mechanical." When atoms are bound together in this way, they form a "molecule."

This theory was developed in the early 20th century and continues to be one of the most significant developments in all of chemistry. It was originally proposed by scientists like Robert J. Van de Waal and then later refined by chemists like Linus Pauling and Richard Tolman. If quantum mechanics applies, then the theory of molecular structure is useful for predicting what elements will bond with each other and under what conditions. It also provides a framework for understanding how molecules interact with light and other molecules. Just as with the atomic theory, the molecular theory can only be proven using the scientific method.

Molecular Weight

In chemistry, one of the most important things to know about a compound is its molecular weight. This number is used to denote the weight of a molecule in atomic units. It can be found by multiplying the number of atoms of each element present in the molecule by their respective atomic masses. For example, the molecular weight of water is 18.0. This is because oxygen has a mass of 16, and hydrogen has a mass of 1.