CHEMICALS ENOTE

WEEK EIGHT

SUBJECT: BASIC SCIENCE

CLASS: GRADE 8

TERM: SECOND

TOPIC: CHEMICALS

MEANING OF CHEMICALS

A chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods. Basically, the chemical compounds are pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances. The field of chemistry is so broad that it would be very difficult to undertake its coverage. Whenever substance undergoes a chemical change, a chemical reaction takes place. Many changes take place during a chemical reaction. A chemical reaction involves some reactants and products. Many of these products are very useful in this modern era.

CLASSES OF CHEMICALS

(A) BASED ON USE

1. Pharmaceutical chemicals

Pharmaceuticals are dependent on fine chemicals of complex, single or pure chemical substances, produced in limited quantities. These fine chemicals are found in many natural products such as chlorophyll, haemoglobin and the vitamins. Peptides, proteins and nucleotides constitute the major categories of pharmaceuticals. Peptides are also used for diagnostics and vaccines. Pharmaceuticals containing more than 2000 different active ingredients are in the market today. Pharmaceutical chemicals are referred to as a synthetic orbio-pharmaceutical products which are widely used in medicines industry, laboratories, sugar industry, etc. Some important chemicals categorized under pharmaceutical chemicals are:

i. Hydrolyzed protein ii. Vitamin iii. Iron supplements iv. Liquid glucose v. Corn syrup

The pharmaceutical industry is the most important customer based chemical industry.

2. Cosmetics

A cosmetic is a substance that is designed to be used on any external part of human body. Cosmetics help to change the odour of the body, to change its appearance, cleanse it, keep it in good condition or to protect it. Some common cosmetics include:

i. Soap ii. Hair dye iii. Mascara iv. Hair removing cream v. Shampoo vi. Perfume vii. Face pack

viii. Moisturizer ix. Lipstick x. Cleanser

All these cosmetics are made from a range of ingredients obtained from synthetic chemicals or naturally occurring chemicals. Some of the well known chemicals used in cosmetics are:

i. Alcohol ii. Ammonium lauryl sulphate iii. Ethoxylated surfactants iv. Imidazolidinylurea

v. Butylatedhydroxytoluene vi. Formaldehyde vii. Lead viii. Lanolin ix. Mercury x. Mineral oils and waxes xi. Oxybenzone xii. Paraben preservatives xiii. Phthalates

Cosmetics use vibrant colours that are obtained from various sources ranging from crushed insects to rust. But none of these colours are manufactured with the help of chemicals. Over the years, the ingredients of cosmetics have changed and now we manufacture our own scents and cosmetics, by using cosmetic formulae. In many countries, colours used in cosmetics are listed as numbers from the Colour Index International. Some common chemicals used in cosmetics are - Isopropyl alcohol, Ammonium lauryl sulphate, Butylated hydroxyl toluene, Diethanolamine,Triethanolamine, Monoethanolamine, Ethoxylated surfactants, formadelhyde, etc.

3. Nuclear chemicals

Nuclear chemistry is the subfield of chemistry dealing with the nuclear chemicals like actinides, radium and radon, etc. One of the important areas is the behaviour of chemicals or materials, used in the nuclear reactions. Uranium and thorium fuel including ores of the elements, fuel fabrication, coolant chemistry, fuel reprocessing, radioactive waste treatment and storage, monitoring of radioactive elements and radioactive geological storage. Some of the radioactive elements used as nuclear chemicals are:

Elements                                    Most Stable Isotope

Astatine                                     At-210

Technetium                               To-91

Radon                                        Rn-222

Promethium                               Pm-145

Francium                                   Fr-223

Polonium                                   Po-209

Radium                                      Ra-226

The nuclear chemistry associated with nuclear fuel (Chemicals) can be divided into two areas:

i. The area which is concerned with operation under the intended conditions

ii. The area which is concerned with meloperation conditions.

4. Agrochemicals

Various chemicals products used in agriculture come under agrochemicals. Generally, they refer to the broad range of pesticides, insecticides, herbicides, fungicides and nematocides. Agrochemicals also include synthetic fertilizers, hormones and concentrated store of raw manure (animal manure). Most of the agrochemicals are toxic to health and environment, especially in the event of accidental spills.

To use the chemicals, some mandatory standards and regulations should be followed by the users. These include: i. Proper storage facilities ii. Emergency cleanup equipment. iii. Safety equipment iv. Good procedure for handling and application v. Proper disposal

5. Industrial chemicals

The chemical industry produces industrial chemicals. In the modern world economy, it converts raw materials (oil, natural gas, air, water, metals and minerals) into more 700 different products. Some of the important chemicals produced are as follows:

i. The first chemical to be produced in large amounts was sulphuric acid. It was the first practical production of sulphuric acid on a large scale in 1736.

ii. Polymers, include all categories of plastics and man-made fibres. The major use of plastics are for packaging, home construction, containers, appliances, pipe, transportation, toys and games. The largest volume of polymer is used in market as polyethylene.

iii. Polyvinyl chloride (PVC), another large volume product which is used to make pipes for construction, siding walls in houses, transportation and packaging materials.

iv. Polystyrene, a large volume of this plastic is used appliances, packaging. toys and other recreation aids.

v. Polypropylene (PP), similar to polyvinyl chloride (PVC) it is used for packaging, appliances, containers, clothing and carpeting.

vi. Many other uses of chemicals are as fibres including polyester, acrylics and polypropylene for apparel. Home furnishing and other industrial as well as consumer use.

All these industrial chemicals are primarily made from LPG (Liquefied Petroleum Gas), natural gas and crude oil. Other basic industrial chemicals include synthetic rubber, resins, surfactant, dyes, pigments and carbon black.

6. Laboratory chemicals

In laboratory, whether it is in a school or in a hospital, a number of chemicals are used. These types of chemicals are called reagents or reactants.

A reagent is a chemical or substance or compound which is added to a system in order to bring about a chemical reaction. The reagents that affect the transformation of an organic substrate are called organic reagents. Collins reagent, Grignard reagent and Fenton's reagent are some examples of organic reagents.

Some reagents are used to confirm the presence of other substances, such reagents are called analytical reagents. Fehling's reagent, Millon's reagent and Tollens' reagents are some examples of analytical reagents.

Generally, the reagents and laboratory chemicals include substances of sufficient purity for use in chemical reactions, physical testing and chemical analysis. Reagents may be either organic or inorganic compounds that are commonly used for analytical purposes. Purity standards for reagents and laboratory chemicals are set by some organizations.

B. CLASSIFICATION OF CHEMICALS BASED ON THEIR HAZARDOUS NATURE

1. Highly hazardous chemicals

Some materials are both toxic and reactive, they are highly harmful to the humans. Such highly hazardous chemicals may cause cancer, miscarriage, birth defects, death and induce genetic damage from relatively small exposures. Some environmental contamination may also result in human exposure through consumption of residues of pesticides in food and drinking water.

These highly hazardous materials are estimated to be fatal to an adult human at a dose of less than 5grams or less than a teaspoon.

Toxicity is the capacity of a substance to poison. Generally, all things are poison and nothing is without poison. It is the dose that determines if the substance is not a poison. So the toxicity of a substance is not an inherent property but the detrimental manifestation of its biochemical effect in a living system. Ingested in very large quantities, even vitamins can exhibit toxicity in humans.

2. Moderately hazardous and toxic chemicals

Moderately hazardous chemicals are substances that are less dangerous to people, wildlife and the environment at any stage. Some of the simple less hazardous chemicals used at our home are antifreeze, gasoline, oven cleaner, drain cleaners, disinfectants, paint thinners, camphor, bleach, engine oil, etc. These are used at our home for different purposes. The moderately hazardous chemicals are labelled as-

i. may cause skin irritation ii. Flammable iii. Vapors harmful iv. May cause burns on contact

Some manufacturers voluntarily list all the ingredients. Packaging also contain many harmful chemicals, so to reduce packaging waste

i. Choose the product in the largest container size available.

ii. Select products in such containers which can be reused or at least recycled.

While using these less hazardous or moderately hazardous chemicals consider the following things

i. Keep them in a child resistant packaging

ii. Take one general cleaner for many purposes.

iii. Do not take different products for different cleaning problems.

iv. Follow the directions given on the label.

v. Leave products in their original containers with labels intact and visible.

vi. Use only that much chemical for what is needed.

vii. We should be aware that only 'Non-toxic' is just an advertising word, we should go through the label and instruction or indication of its safety.

3. Non-hazardous and non-toxic chemicals

There are many chemicals that are not harmful or hazardous for living beings as well as for their environment.  Such chemicals can be safely disposed off. Some non-hazardous chemicals include certain salts many natural products and some inert materials like resins and gels Such materials do not exhibit any hazardous

characteristics and hence can be disposed off with normal trash.

Some of the common non-hazardous and non-toxic chemicals are:

i. Actin   ii. Agarose  iii. p-Alamine  iv. Arginine  v. Amylase  vi. Arginase  vii. Betaine viii. Bile salts ix. Cytosine x. Calcium citrate xi. Cellulose xii. Dextrose xiii. Egg albumin xiv. D-fructose xv. Gelatin xvi. Glass beads xvii. Iron filings xviii. Lactofermin xvix. Glucamic acid

xx. Pyridoxal phosphate xxi. Renin xxii. Methyl cellulose xxiii. Pectin xxiv. Riboflavin xxv. Sucrose (table sugar) xxvi. Starch xxvii. Trypsin inhabits

we use many non-toxIC chemicals in our kitchens. We can use simple and relatively safe ingredients to perform most home-cleaning chores in place of many hazardous chemicals. Some of these are; i. Baking soda  ii. Borax iii. Isopropyl alcohol iv. Mineral oil v. Cornstarch vi. Lemon juice vii. Vinegar viii. Soap

SAFETY MEASURES WHEN USING CHEMICALS

i. Do not attempt to identity the chemicals by smell or taste.

ii. Avoid eating, drinking or application of cosmetics in laboratory.

iii. Handle and store laboratory glassware with care. Do not use damaged glassware and short clothes. Wear shoes at all times in the laboratory.

iv. Clearly label and properly store all chemicals and equipment.

v. Fire extinguishers must be tagged, charged and dated.

vi. Weekly check of fire extinguishers must be tagged, charged and dated.

vii. Stairwells should be clear and unobstructed.

viii. Alert all occupants by sounding the building alarm system from the manual pull stations located at the exit stairways throughout the building.

vix. When opening newly received reagents immediately read the warning labels to be aware of any special storage precautions such as refrigeration or inert atmosphere storage.

x. Check chemical containers periodically for rust, corrosion and leakage.

xi. Store bottles of especially hazardous and moisture-absorbing chemicals in chemical safe bags.

xii. Limit the amount of flammable and combustible materials stored to that required for one year of laboratory work.

xiii. Store flammable and combustible liquids in their original containers or safety cans. The container should have a spring closed spout cover and an integral flame-arrester.

xiv. Proper disposal of used chemical materials and chemicals with expiry dates.

xv. Follow the safety instructions suggested on the labelling of a chemical product.

ACID:  An Acid is a sour-tasting substance that releases hydrogen ions when added to water. Examples of acid;  hydrochloric acid, tetraoxosulphate (vi) acid, trioxonitrate (v) acid, tartaric acid, etc.

BASES:  A base is a substance that can accept hydrogen ions in water and can neutralize an acid. It has soapy or slippery feel. Examples of bases are sodium hydroxide, ammonia, calcium hydroxide, etc.

SALT: A salt is an ionic compound that contains a cation ( from base) and an anion (from acid). Examples of salts; table salt, potassium chloride, potassium iodide, etc

ASSIGNMENT

1. What is a chemical substance?

2. Classify chemicals based on their uses and give two examples of each.

3. Classify chemicals based on their hazardous nature.

4. State three safety measures to be observed when handling chemicals.