💫LEARN QUICK REVIEW OF IMPORTANT CHEMISTRY TERMS💫

🔶LEARN QUICK REVIEW OF IMPORTANT CHEMISTRY TERMS🔶

Anything that occupies space and has mass is called matter. 

• The space anything occupies is called its volume.

• The amount of matter anything contains is called its mass.

• Matter is made up of extremely small particles called molecules. 

• There is some space, called intermolecular space, between the molecules.

• Molecules are held together by a force, called intermolecular force, or cohesion.

• Matter exists in three states-solid, liquid and gaseous. e Important properties of solids, liquids and gases can be understood in terms of intermolecular space and intermolecular force.

• The change in state of matter from one to another is called interconversion of state. An element is a substance that cannot be split into simpler substances by chemical means. • A compound is a substance that can be split or broken down into simpler substances by chemicalmeans. 

• Matter is made up of extremely small parts, called molecules, that can exist independently. 

• Molecules are made up of still smaller parts, called atoms, which do not generally exist independently.

A molecule of an element is made up of atoms of only one kind. A molecule of a compound is made up of atoms of two or more kinds, i.e., two or more

• The force that holds atoms together is called a chemical bond.

• A chemical bond is much stronger than an intermolecular force elements• A change is said to be reversible when the opposite change can be brought about by reversing the condition

• A change is said to be irreversible when the opposite change cannot be brought about by reversing condition

• A change in which no new substances are formed and which can be reversed by reversing conditions is called a physical chang

• A change in which new substances are formed and which cannot be reversed by reversing conditions is called a chemical change. 

• The mass of the individual substance(s) undergoing a chemical change is altere

Physical and chemical changes can take place together, as in the burning of a candle.

• A change in energy takes place when a physical or a chemical change occurs.

Energy changes usually involve the emission or absorption of heat. They may also involve the emissionor absorption of light.

Substances can be classified as pure substances and mixtures.

A pure substance is one that cannot be split into simpler substances by a physical means such as filtration, sublimation or distillation. Elements and compounds are pure substances.

• An element is a substance that cannot be split into simpler substances by a Elements are represented by symbols.chemical means.

A compound is a substance that can be split into simpler substances by a chemical means.

Compounds are represented by formulae.

• Elements combine in fixed proportions of atoms and mass to form a compound.

The properties of a compound are entirely different from those of the constituent elements.

• A mixture is a substance that can be separated into two or more pure substances by a physical

means such as filtration, sublimation or distillation.

The components of a mixture 

• may be present in it in any proportion,

• coexist without reacting with each other,

• retain their properties, and

• can be separated from one another by physical means.

A mixture with the same composition and properties throughout is called a homogeneous mixture. 

• When the different parts of a mixture differ in composition and properties, it is said to be heterogeneous

The components of solid mixtures are separated by magnetic separation, sublimation, dissolution evaporation and chromatography,

Chromatography is based on the principle of adsorption.

• The components of solid-liquid heterogeneous mixtures are separated by sedimentation and decantation, filtration and distillation. Distillation is used to separate the components of solid-liquid homogeneous mixtures too. 

• A separating funnel is used to separate immiscible liquids.

Metals are generally hard, strong solids. They are lustrous, sonorous, malleable, ductile, and good conductors of heat and electricity.

• Nonmetals are lustreless (except graphite and iodine), brittle if solid, non sonorous, bad conductors of heat, and bad conductors of electricity (except graphite).

• Metalloids or semimetals are a set of elements (boron, silicon, germanium, arsenic, antimony and tellurium) with properties intermediate between those of metals and nonmetals.

 • The semiconducting properties of metalloids make them important in the electronics industry.

• The chemical action of moist air on metals is called corrosion.

In moist air, a piece of iron rusts. Rust is represented by the formula Fe 03.XH,O.

 • Corrosion can be prevented by painting, greasing, galvanising, electroplating and alloying the metal.

• An atom is the smallest part of an element that can take part in a chemical reaction. A molecule is the smallest part of an element or a compound that is capable of existing independently.

• The combining capacity of an element with other elements is known as its valency. The valency an element is given by the number of hydrogen atoms an atom of the element combines with or displaces from a compound.

• Some elements show different valencies in different compounds. Such elements are said to have variable valency.

The number of atoms contained in a molecule of an element or a compound is known as its atomicity.

• Radicals are atoms or groups of atoms behaving like single atoms but having a charge on them. They have a valency and usually remain intact in a chemical reaction. • The valencies of elements of groups 1, 2, 13 and 14 of the periodic table are 1,2,3 and 4, and those of groups 15, 16, 17 and 18 are 3, 2, 1 and 0.

• Air is a mixture of gases.

By volume, it contains about 78% nitrogen and 21% oxygen. The remaining 1% consists of several gases like argon and other noble gases, carbon dioxide, water vapour, etc. Besides, smoke and dust arealso present

• Oxygen can be prepared by decomposing hydrogen peroxide using manganese dioxide as a catalyst. A catalyst is a substance generally used to speed up a reaction without being changed itself.

• A reaction in which a substance adds on oxygen is called oxidation.

• When a substance combines with oxygen giving out heat and light, the phenomenon is called combustion Oxygen is essential for respiration.

• The slow conversion of iron into reddish brown hydrated iron(III) oxide by the action of moist air is known as rusting. The reddish brown product Fe.O, XH,O is known as rust.

• A glowing splinter burns with a flame in oxygen. This is a test for oxygen.

• Nitrogen is obtained on a large scale by the fractional distillation of liquefied air. Nitrogen is indirectly used by plants for the synthesis of proteins and nucleic acids.

• Carbon dioxide (i) extinguishes a burning splinter, (ii) turns moist blue litmus wine-red, and (iii) turns limewater milky.

• Carbon dioxide is used by plants for photosynthesis.

• Air containing harmful substances is called polluted air. The common pollutants of air are carbon monoxide, sulphur dioxide, oxides of nitrogen, soot and dust.

• Acid rain contains mainly sulphuric and nitric acids.

• Acid rain has harmful effects on plants, animals, soil, sculptures, monuments and buildings.