Selina Concise Chemistry Class 6 ICSE Solutions Chapter 1 ... - Free Printable

Question 2: Short Answers

#### (a) What is science?
Answer:
Science is the systematic effort by human beings to control nature through experiments and observation for their own use. Alternatively, it can be defined as the systematic ongoing effort by human beings to study, understand, and utilize nature for meaningful purposes. This understanding is slowly developed through careful observations and experiments.

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#### (b) What is chemistry?
Answer:
Chemistry is the branch of science that deals with the composition, structure, properties, and reactions of matter. It studies how substances interact with each other and how they can be transformed into new substances. Chemistry focuses on atoms, molecules, and the chemical processes that occur at the molecular level.

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#### (c) What is a fuel?
Answer:
A fuel is a substance that undergoes combustion or chemical reaction to release energy, typically in the form of heat or light. Fuels are used to power engines, generate electricity, and provide heat for various applications. Common examples include fossil fuels (e.g., coal, oil, natural gas), biofuels (e.g., ethanol, biodiesel), and nuclear fuels (e.g., uranium).

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#### (d) How is chemistry helpful in improving the health of human beings?
Answer:
Chemistry plays a crucial role in improving human health in several ways:
1. Medicines and Pharmaceuticals: Chemists develop drugs and medicines to treat diseases and alleviate symptoms. Understanding the chemical structures and interactions of molecules allows scientists to design effective treatments.
2. Nutrition: Chemistry helps in understanding the nutritional content of foods and the biochemical processes involved in digestion and metabolism.
3. Vaccines: Chemical research is essential for developing vaccines that protect against diseases by stimulating the immune system.
4. Diagnosis: Chemical tests and analyses are used in medical diagnostics to detect diseases and monitor health conditions.
5. Hygiene and Sanitation: Chemicals are used in disinfectants, antiseptics, and cleaning agents to maintain hygiene and prevent the spread of infections.
6. Water Purification: Chemical processes are used to purify water, making it safe for drinking and reducing the risk of waterborne diseases.

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#### (e) What is alchemy?
Answer:
Alchemy is an ancient practice that predates modern chemistry. It was a philosophical and proto-scientific tradition that sought to transform base metals into precious metals (such as gold) and to discover the "Philosopher's Stone," a mythical substance believed to have magical powers, including the ability to grant immortality and transmute metals. Alchemists also explored the nature of matter, the elements, and the principles of change, laying some foundational ideas for later developments in chemistry.

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#### (f) What kind of experiments did Alchemists do?
Answer:
Alchemists conducted a variety of experiments, often involving:
1. Metal Transmutation: They attempted to transform base metals like lead into gold using mixtures of chemicals and heating processes.
2. Mixing Substances: They combined different substances to observe chemical reactions and changes in properties.
3. Distillation and Filtration: These techniques were used to separate and purify substances.
4. Heating and Melting: Alchemists heated materials to high temperatures to observe changes in their states and properties.
5. Symbolic and Philosophical Experiments: Many alchemical experiments had symbolic meanings related to spiritual and philosophical beliefs about the nature of the universe.

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#### (g) What is ‘Philosopher’s stone’?
Answer:
The Philosopher's Stone is a legendary substance in alchemy. It was believed to have the power to:
1. Transmute Metals: Convert base metals like lead into precious metals such as gold.
2. Achieve Immortality: Bestow eternal life or prolong human lifespan.
3. Cure Diseases: Act as a universal elixir capable of healing all ailments.
The Philosopher's Stone was considered the ultimate goal of alchemical research, symbolizing perfection and the mastery of nature.

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#### (h) What is the main difference between alchemy and chemistry?
Answer:
The main differences between alchemy and chemistry are:
1. Purpose:
- Alchemy: Focused on mystical, philosophical, and spiritual goals, such as transmuting metals and achieving immortality.
- Chemistry: Focuses on scientific inquiry, experimentation, and understanding the physical and chemical properties of matter.
2. Approach:
- Alchemy: Often relied on symbolism, metaphysics, and unscientific methods.
- Chemistry: Emphasizes empirical evidence, reproducible experiments, and the scientific method.
3. Outcome:
- Alchemy: Did not produce verifiable results or contribute to practical knowledge.
- Chemistry: Has led to numerous practical applications, such as medicine, materials science, and technology.

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#### (i) Name the chemicals which help in increasing food production.
Answer:
Chemicals that help increase food production include:
1. Fertilizers: Such as nitrogen, phosphorus, and potassium compounds, which provide essential nutrients to plants.
2. Pesticides: Chemicals used to control pests and diseases that damage crops.
3. Herbicides: Used to eliminate weeds that compete with crops for resources.
4. Growth Regulators: Hormones and chemicals that promote plant growth and development.
5. Irrigation Chemicals: Substances used to improve soil quality and water retention.
6. Seeds Coatings: Chemicals applied to seeds to protect them from pests and diseases during germination.

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#### (j) Name six such products, which we use daily.
Answer:
Six everyday products that involve chemistry include:
1. Soap and Detergents: Used for cleaning and hygiene.
2. Plastic Bottles: Made from polymers for packaging and storage.
3. Medicines: Such as antibiotics and pain relievers.
4. Cosmetics: Like shampoos, lotions, and makeup.
5. Food Additives: Preservatives, flavorings, and colorings in processed foods.
6. Gasoline and Diesel: Fuels used in vehicles.

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#### (k) How is the knowledge of chemistry important to mankind?
Answer:
The knowledge of chemistry is crucial to mankind for several reasons:
1. Health and Medicine: Chemistry enables the development of life-saving drugs, vaccines, and diagnostic tools.
2. Energy Production: Chemical processes are central to producing energy from fossil fuels, nuclear reactions, and renewable sources.
3. Materials Science: Chemistry helps create new materials for construction, electronics, and transportation.
4. Environmental Protection: Understanding chemical reactions aids in addressing pollution, climate change, and resource management.
5. Food Production: Chemistry improves agricultural practices, ensuring food security and nutrition.
6. Technology and Innovation: Chemistry drives advancements in fields like nanotechnology, biotechnology, and information technology.
7. Daily Life: From cleaning products to cosmetics, chemistry enhances the quality and convenience of everyday life.

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Final Answer:

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\text{(a) Science is the systematic effort by human beings to control nature through experiments and observation for their own use.}
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