Introduction to Chemistry

Science is the systematic accumulation of observations and experiments carried out by scientists, whose intensive research paves the way for the progress of mankind.

Science is bifurcated into three main branches:

1. Physics — It deals with different forms of energy such as light, sound, heat and electrical energy, and with physical changes correlated with energy changes.
2. Chemistry — It deals with the study of substances, their composition and properties, their interaction with other substances and the chemical changes they undergo.
3. Biology — It deals with the study of living organisms, e.g. plants (Botany) and animals (Zoology).

a. Glass test tube — It is a special glass tube with one open and one closed end, used for heating chemicals and studying reactions in solution.

b. Hard glass boiling tube — It is a hard glass test tube made of pyrex, which is resistant to chemicals and is used for heating chemicals for special purposes.

c. Beaker — It is a glass container with a lip, used for holding, pouring and mixing solutions.

d. Round bottom flask — It is used for the preparation of gases where heating is required, since the round bottom distributes heat uniformly throughout on heating.

e. Retort — It is used for carrying out distillation experiments, which include the distillation of acids.

A round bottom flask is preferred to a flat bottom flask during the preparation of gases because the round bottom distributes heat uniformly throughout on heating. A flat bottom flask is used only where heating is not required, as uniform heat distribution is not necessary in that case.

a. The wooden handle at the end of the test tube holder — The wooden handle, being a poor conductor of heat, makes holding the test tube holder easy and safe when the substance is heated.

b. The asbestos fixed at the centre of the wire gauze — It prevents the glass apparatus from cracking when heated from below and helps in the even distribution of heat to the bottom of the apparatus.

c. The clamp mounted on the rod of a retort stand — It holds the apparatus (e.g. flasks) used during chemical reactions and can be adjusted upwards or downwards.

d. The air regulator in a bunsen burner — It is a metal cylinder with holes used for regulating the flame.

e. The tap at the base of a burette — The measured liquid is removed dropwise by opening the tap below.

a. Oxygen — Collected by downward displacement of water, since it is insoluble or only slightly soluble in water.

b. Ammonia — Collected by downward displacement of air, since it is soluble in water and lighter than air.

c. Sulphur dioxide — Collected by upward displacement of air, since it is soluble in water and heavier than air.

Importance of Chemistry in agriculture:

1. Fertilizers — Chemistry has helped produce fertilizers that improve fertility and supply plant nutrients essential for growth. Examples: ammonium nitrate, urea, phosphatic fertilizer.
2. Pesticides — Chemicals added to the soil to kill unwanted plants and harmful insects, e.g. herbicides (kill unwanted plants) and insecticides (destroy harmful insects).

Importance of Chemistry in the production of various products:

Knowledge of Chemistry has initiated the production of different products obtained through chemical reactions, such as:

• Food — Refined oils, butter and cheese.
• Construction — Mortar, cement and glass.
• Clothing — Natural fabrics such as silk.
• Household — Cooking gas (LPG) and food preservatives.
• Daily usage — Paints, dyes, perfumes, paper and ink.
• Industrial — Metals and alloys used in machines and metallic structures like automobiles.
• Petroleum — Petrol, kerosene and diesel oil.

Alchemists were the predecessors of modern chemists. Alchemy and alchemists are older words for Chemistry and chemists. Alchemists transformed or created substances through processes that appeared magical.

They were largely discredited by the scientific community since their work included occult and religion. For example, Nicolas Flamel, an alchemist around the 14th century, claimed to transform metals into gold. Although alchemy is today considered a pseudoscience, alchemists were successful in developing processes to extract metals and prepare alloys, which helped later chemists develop path-breaking avenues in Chemistry.

The philosopher's stone was a legendary substance believed to be capable of turning inexpensive metals like lead or mercury into gold and silver. It was not literally a stone, but a powder or potion. It was also believed to be the elixir of life and, for a long time, was the most sought-after goal in Western alchemy.

From the Middle Ages to the 17th century, the philosopher's stone remained one of the main goals of alchemy. During this period, alchemists developed processes that later helped chemists to extract metals and develop new avenues in Chemistry.

a. Dimitri Mendeleev — He was a Russian scientist who formulated the Periodic Table of elements. He systematically arranged the dozens of known elements and could even predict the properties of the still unknown elements. He is best known for his discovery of the Periodic Law.

b. Antoine Lavoisier — He was a French scientist who recognised and named Oxygen in 1778 and later Hydrogen in 1783. He wrote the first extensive list of elements and, through his famous combustion experiment (heating pure mercury in a swan-necked retort), led to the discovery of Oxygen.

c. John Dalton — He was an English scientist who compiled Dalton's atomic theory in 1803. Its main postulate is that matter consists of particles called atoms, which are indivisible and cannot be created or destroyed. The theory was later contradicted in certain aspects by the modern atomic theory.

Cosmetics — Cosmetics are products that enhance or alter the appearance or fragrance of an individual. They are mixtures of chemical compounds obtained from natural or synthetic sources.

Talc — Talcum powder is made from talc, a mineral made up of the elements magnesium, silicon and oxygen. Talc absorbs moisture, cuts down on friction, keeps the skin dry and prevents rashes.

Two main ingredients in cosmetics and their roles:

1. Water — It forms the base of almost all cosmetic products and acts as a solvent for water soluble ingredients.
2. Oxide of titanium — It is a natural pigment powder which gives mild sun protection.

Terylene — It is a synthetic polyester fibre or fabric formed generally by the addition of polyester to the natural fibre cotton.

Characteristic properties of Terylene:

• It is a strong fabric.
• It is elastic in nature and resistant to friction.
• It suffers little loss in strength.
• It is crease resistant.
• It is easily washable and dries quickly.

Medicines are natural or synthetic substances which, when taken in a living body, affect its functioning and treat or prevent a disease. Chemistry allows researchers to create drugs that combat illness, helping to cure and prevent diseases and increasing the life span of human beings. In this way, medicines are a boon to mankind.

Aspirin

• Positive effects: It treats pain, fever and inflammation. Given shortly after a heart attack, it may decrease the risk of death, and long-term use may reduce blood clots in people who are at high risk.
• Negative effects: Its side effects may include upset stomach and stomach ulcers.

Paracetamol

• Positive effects: It treats mild to moderate pain and fever, and may also be used for low back pain, headaches and dental use. It is safe at recommended doses.
• Negative effects: Too high a dose may result in liver problems.

Advantage of detergents over soap: Ordinary soap, when rubbed in hard water, is wasted and lather forms only after all the insoluble salts in hard water are removed as scum. Synthetic detergents, on the other hand, do not form scum and lather even in hard water.

Stain removal — It is the process of removing a mark or stain left by one substance on a specific surface, such as fabric. Most stains are removed by dissolving them with a solvent.

Three important stain removers and their prime functions:

1. Lemon juice — It is used for removing stains from fabrics.
2. Sodium hydroxide — It dissolves grease and oil and is preferred as a drain cleaner.
3. Boiling water — It softens fruit juice stains on a fabric.

Physics

Reason — Physics deals with the different forms of energy such as light, sound, heat and electrical, and the physical changes correlated with energy changes. Chemistry deals with the study of substances, their composition and properties. Biology deals with the study of living organisms.

Organic Chemistry

Reason — Organic Chemistry includes the study of specific carbon compounds built up mainly of carbon and hydrogen. Inorganic Chemistry includes the study of elements and compounds including metals and non-metals. Physical Chemistry deals with the study of the physical properties of substances and the laws and principles governing chemical reactions and changes.

Demitri Mendeleev

Reason — Demitri Mendeleev formulated the Periodic Table of elements and is best known for his discovery of the Periodic Law. John Dalton compiled Dalton's atomic theory. Daniel Rutherford is known for the discovery of nitrogen.

Alchemists

Reason — Alchemists were the predecessors to the modern chemist who created the legendary philosopher's stone. Botanists study plants and physicists study energy and physical changes; neither created the philosopher's stone.

Terylene

Reason — Terylene is a synthetic polyester fibre used in clothing. Cotton and jute are natural fibres, not synthetic.

Aspirin

Reason — Aspirin is a medicine used to treat pain, fever and inflammation. An anaesthetic is used to cause loss of sensation, and an antacid is used to treat acidity and upset stomach.

Detergent

Reason — A detergent is a synthetic water soluble cleaning agent that does not form scum and lathers even in hard water. Soap is wasted in hard water as it forms scum. A cleanser is a general cleaning agent and not the specific answer here.

Talc

Reason — Talc absorbs moisture, cuts down on friction, keeps the skin dry and prevents rashes. A preservative extends shelf life, and an emulsifier gives an even texture to creams and lotions.

Benzoic acid

Reason — Benzoic acid is used as a food preservative for jams, pickles and carbonated drinks. Titanium dioxide is a cosmetic ingredient and rayon is a synthetic fibre.

Sodium hydroxide

Reason — Sodium hydroxide dissolves grease and oil and is preferred as a drain cleaner. Glycerine and hydrogen peroxide are not used for this specific purpose.

Round bottom flask

Reason — A round bottom flask is used for gas preparations where heating is required, as its round bottom distributes heat uniformly throughout on heating.

Test tube stand

Reason — A test tube stand has holes and upright pegs on which washed test tubes can be inverted and held.

Boiling Tube

Reason — A boiling tube is a hard glass test tube made of pyrex, which is resistant to chemicals and used for heating specific liquids for special purposes.

A Tripod stand

Reason — A tripod stand is a metallic apparatus made of an iron triangle on three iron legs, which supports the glass apparatus and the wire gauze placed on it.

Gas jar

Reason — A gas jar is a long glass jar that is closed at one end and open at the other, used for collecting gases by different methods.

Pipette

Reason — A pipette measures liquid by sucking the liquid up to the marked level and closing the open end; the measured liquid is then poured out by removing the thumb.

Thistle funnel

Reason — A thistle funnel is a long glass tube with a broad inlet at the top, which allows the entry of reactants into the round bottom flask during the preparation of gases.

Beehive shelf

Reason — A beehive shelf is a clay vessel with two outlets, kept in a trough of water during the collection of a gas by the downward displacement of water.

Bunsen burner

Reason — A bunsen burner is a modern apparatus consisting of a burner tube, an air regulator and a base, used for heating purposes.

Wire gauze

Reason — A wire gauze is a rectangular wire mesh with asbestos at its centre, placed between the tripod stand and the glass apparatus to prevent cracking on heating.

Alchemy was considered a pseudoscience because it included occult and religious practices. Towards the end of the 17th century, scientific processes involving modern Chemistry began to develop, and Chemistry gained recognition as a scientific field.

Preservatives are added to food or beverages to prevent decomposition by bacteria or microbes, to reduce the risk of food borne infections and to preserve the nutritional quality of food.

Titanium dioxide is an important ingredient in cosmetics because it is a natural pigment powder which gives mild sun protection.

Aspirin is one of the most widely used medications globally because it treats pain, fever and inflammation. Given shortly after a heart attack, it may decrease the risk of death, and its long-term use may reduce blood clots in people who are at high risk.

Ordinary soap is wasted in hard water because hard water does not lather with soap. When rubbed in hard water, the soap forms lather only after all the insoluble salts in the hard water are removed as scum, so a large amount of soap is wasted.

A philosopher's stone is not exactly a stone because it was not literally a stone, but a powder or potion believed to turn inexpensive metals into gold and silver.

Food processing is an important procedure for obtaining marketable food products because it transforms or changes the raw ingredients in food into easy usable forms through processes like mincing, cooking, canning and packaging, thereby making them suitable for the market.

Cosmetics may contain preservatives because preservatives extend the shelf life of a cosmetic and may prevent the growth of microorganisms in it.

Polyester is added to the natural fibre cotton to give terylene because this combination makes the fabric strong, crease resistant, easily washable and quick drying.

All medicines must be taken under a doctor's supervision and in the correct dose because an incorrect or excessive dose may cause harmful side effects. For example, aspirin may cause an upset stomach and stomach ulcers, while too high a dose of paracetamol may result in liver problems.