Introduction to Chemistry
A. Choose the correct option.
1. The systematic study of the natural world, based on facts learned by careful observations and experimentation is called
i. Biology. [ ]
ii. Physics. [ ]
iii. Science. [✓]
iv. Chemistry. [ ]
2. People who work for the development of science through experimentation and observation are called
a. scientists. [✓]
b. chemists. [ ]
c. physicists. [ ]
d. biologists. [ ]
3. A detailed study of all kinds of substances present in nature is covered under the branch of science called
a. Biology. [ ]
b. Physics. [ ]
c. Chemistry. [✓]
d. Zoology. [ ]
4. Scientists who study about Chemistry are called
a. biologists. [ ]
b. physicists. [ ]
c. botanists. [ ]
d. chemists. [✓]
5. The study of elements and compounds other than carbon or hydrocarbon is done in the branch of Chemistry called
a. Organic Chemistry. [ ]
b. Inorganic Chemistry. [✓]
c. Physical Chemistry. [ ]
d. Stoichiometry. [ ]
B. State whether True or False(T/F).
1. Inorganic chemistry is the study of elements and compounds other that carbon or hydrocarbons. [T]
2. Organic Chemistry is the study of the principles and methodologies of Chemistry. [F]
3. The medieval predecessor of Chemistry is called Alchemy. [T]
4. Alchemists believed the metals to be alive and growing underground. [T]
5. Antoine Lavoisier, the French scientist, first established that air contains more than one gas. [T]
C. Fill in the blanks.
1. Alchemists believed that they could refine base metals into precious metals, if they could find the substance called philosopher's stone.
2. The first scientist who made a clear distinction between Alchemy and Chemistry was Robert Boyle.
3. Antoine Lavoisier was able to show the relationship between oxygen and metal, resulting in rust.
4. Henry Cavendish discovered hydrogen gas.
5. Marie Sklodowska-Curie was the first woman to win a Nobel Prize and the only person to win it in multiple branches of Science.
D. Give one word for the following:
1. the branch of Chemistry which deals with the study of carbon and its compounds.
= Organic Chemistry;
2. the medieval predecessor of Chemistry.
= Alchemy;
3. a mixture that is made by combining two or more metals.
= Alloy;
4. the chemist who arranged the elements according to their weights in the periodic table.
= Dmitri Mendeleev;
5. the products designed to cleanse, protect and enhance our physical appearance.
= Cosmetics.
E. Short answer type questions.
1. List three broad classifications of science.
= Science has been broadly classified into three main branches - Physics, Chemistry and Biology.
2. What is the experiment to measure the density of the Earth called?
= The experiment to measure the density of the Earth is called the Cavendish experiment.
3. What is the periodic table?
= To organise elements according to their weight and chemical reactivity, in a tabular form knowing as the periodic table.
4. Name some common chemical preservatives.
= Some common chemical preservatives are - sorbic acid, benzoic acid, sulphites (sulphur dioxide, sodium bisulphate and potassium hydrogen sulphite) and nitrites such as sodium nitrite.
5. What did the early human wear?
= The early humans wore light fabrics made from cotton and flax, which grew in the valleys of the Ganges and the Nile, respectively. In winter, the clothes made from wool were used as clothing, which is mainly obtained by rearing sheep.
F. Long answer type questions.
1. How is Alchemy different from Chemistry?
= The first scientist who made a clear distinction between Alchemy and Chemistry was Robert Boyle in his book called 'The Sceptical Chemist'(1661). Although both Alchemy and Chemistry are concerned with matter, the major difference between these two branches of knowledge is that chemists apply scientific method to their work.
2. Were the alchemists successful in transforming base metals into gold? What were they successful in?
= During their quest for transformation of metals into gold, alchemists performed various experiments with different metals and recorded the results. Although they were unsuccessful in their quest, their experiments and records laid the foundation for the development of the systematic branch of knowledge - Chemistry. The alchemists were, however, successful in developing process to extract metals such as iron, and also prepare alloys such as bronze.
3. Write a short note on the contribution of the following scientists in increasing our knowledge of Chemistry.
a. Dimitri Mendeleev.
= Dimitri Mendeleev(1834-1907) was a Russian chemist and inventor. He helped to transform the world of Science with his way of organising elements according to their weight and chemical reactivity, in a tabular form known as the periodic table (Mendeleev's Periodic Table), which is used in Chemistry and Physics. In addition to the creation of the periodic table, Mendeleev worked on the spectroscope and the capillarity of liquids, both of which continue to be in use till today.
b. Marie Sklodowska-Curie.
= Marie Sklodowska-Curie(1867-1934) was a physicist and chemist, well-known for the theory of radioactivity. She was the first woman to win a Nobel Prize and the only person to win it in multiple branches of science. In December 1903, she shared the Nobel Prize in Physics with Pierre Curie and Henri Becquerel for their joint research on radiation.
4. Write a short note on.
a. Food and Chemistry.
= Microorganisms such as bacteria, fungi (such as yeast and Rhizopus) spoil the food items and make them unfit for consumption. So, the food items need to be preserved. Chemistry plays an important role in the methods of food preservation. Common methods of food preservation include - salting, drying, cooking, refrigeration and freezing, canning, using spices, pickling, pasteurising and many more.
Chemical preservatives are also added to process food such as ketchups, jams or pickles to prevent them from rotting and spoiling. Some common chemical preservatives are sorbic acid, benzoic acid, sulphites (sulphur dioxide, sodium bisulphite and potassium hydrogen sulphite) and nitrites such as sodium nitrite.
Chemistry has major importance in food processing sector. Food processing such as refined oils, curd, cheese, butter, beverages and baby food are products of chemical processing.
b. Cosmetics and Chemistry.
= Cosmetics are as excellent example of how discoveries in Chemistry are part of our day-to-day lives. Cosmetics, also known as beauty products, are the products designed to cleanse, protect and enhance. These are made from combinations of chemicals and thus fall into the field of Chemistry. Cosmetics include perfumes, lipsticks, nail enamels, talcum powder, hair dyes, foundation, eyeliner and hairspray.
The main ingredients present in most of the cosmetics include water, emulsifiers, thickeners, moisturisers, colours and fragrances. All these ingredients are made up of chemical compounds. For example, talcum powder is made from a compound called talc, which is composed of magnesium, silicon, oxygen and hydrogen.
5. How has Chemistry influenced modern medicine?
= Most of the medicines used today are manufactured through chemical processes. Chemists have discovered a number of medical drugs, which help to fight diseases. Tetracycline and other antibiotics are used to kill germs and cure diseases.
Medicines such as penicillin, aspirin and paracetamol have saved many lives. Surgeries and therapies are made painless and safe by the use of chemicals such as anaesthetics and antiseptics. All these are nothing but the contribution of Chemistry.