Chemistry Class 9 Chapter 1: Nature of Science in Chemistry

a) Analytical chemistry deals with methods and instruments for determining the composition and properties of matter.

b) Medicinal chemistry studies the interaction between drugs and biological targets and the development of new medicinal agents.

c) Inorganic chemistry deals with elements and their compounds except organic compounds.

a) Nuclear chemistry deals with the changes that occur in atomic nuclei.

b) Environmental chemistry deals with chemical and toxic substances that pollute the environment and their adverse effects on human beings.

c) Astrochemistry deals with chemical processes and reactions in stars, planets, comets and interstellar space.

Organic chemistry deals with substances containing carbon (except carbonates, bicarbonates, oxides and carbides), e.g. methane, ethanol. Inorganic chemistry deals with elements and their compounds except organic compounds, e.g. NaCl, iron.

a) Industrial chemistry (large-scale production of cement). b) Inorganic chemistry (NH₄Cl is an inorganic compound; it breaks up on heating and the vapours join again). c) Biochemistry (photosynthesis is a process in living organisms).

a) Nuclear chemistry (radiotherapy uses radioactive sources). b) Organic chemistry (hydrocarbons are carbon compounds). c) Inorganic chemistry (extraction of pure metals from ores; if the extraction is on a large scale it also involves industrial chemistry).

Chemistry is the science that studies matter, its properties, composition and its interactions with other matter and energy. It also deals with the changes that matter undergoes.

Chemistry is the science that investigates the materials of the universe and the changes they undergo. It deals with composition, structure, properties, behaviour and changes of matter and energy.

Example: when LPG burns, the gas (matter) reacts with oxygen (other matter) and gives heat and light (energy).

Earth – solids; Air – gases; Sea – liquids; Sky – plasma.

It means that matter takes in or gives out energy (heat, light, electricity) when it changes. Example: a candle burns and gives heat and light; or wood burns in a chulha and gives heat.

Chemical changes are always accompanied by energy changes. Matter changes into new substances while heat, light or electricity is absorbed or released, so both must be studied together.

Green chemistry is the design of chemical products and processes that reduce the use of hazardous substances. It lowers pollution because fewer harmful chemicals are made or released into air and water.

Rust is a new substance formed from iron, oxygen and water. The composition of the matter changes, and chemistry studies the composition of matter and its changes.

Composition: 40% carbon, 6.7% hydrogen, 53.3% oxygen. Property: melting point 17 °C (and liquid at room temperature). Interaction with other matter: it reacts with sodium carbonate and gives a gas.

New substance: a new plastic or detergent. Drug: a new pain-killer tablet. Technology: a rechargeable lithium-ion battery or water filter. (Any suitable examples.)

Chemistry studies the composition of matter and its changes. In warm conditions, substances in milk change into new substances such as lactic acid, so its composition changes and it tastes sour.

Matter is anything that has mass and occupies space. Examples: iron nail (solid), water (liquid), oxygen (gas).

The definition links the sky with plasma. The Sun is made of hot ionised matter, which is plasma.

a) Organic chemistry deals with substances containing carbon (except carbonates, bicarbonates, oxides and carbides).

b) Physical chemistry deals with laws and theories used to understand the structure and changes of matter.

c) Biochemistry deals with the physical and chemical changes in living organisms.

a) Industrial chemistry deals with the large-scale production of chemical substances.

b) Polymer chemistry deals with polymers, their types, properties, uses and polymerisation.

c) Geochemistry deals with the composition, distribution and transformation of elements and compounds in the Earth's crust (rocks, minerals, soils, water, atmosphere).

Geochemistry studies the chemical composition, distribution and changes of elements and compounds in the Earth's crust (rocks, minerals, soils, water). Astrochemistry studies chemical processes and reactions in stars, planets, comets and interstellar space.

Analytical chemistry deals with methods and instruments to find the composition and properties of matter. Environmental chemistry deals with the chemical and toxic substances that pollute the environment and their effects on human beings.

Biochemistry studies the physical and chemical changes in living organisms. Medicinal chemistry studies the interaction between drugs and biological targets and the development of new medicinal agents.

Industrial chemistry is concerned with large-scale production of any chemical substance. Polymer chemistry studies one kind of substances only, the polymers: their types, properties, uses and polymerisation.

Organic chemistry studies carbon compounds (hydrocarbons, alcohols, acids, etc.), whether made in a laboratory or found in nature. Biochemistry studies the physical and chemical changes that occur in living organisms.

Differences: (1) organic chemistry deals with carbon compounds (except carbonates, bicarbonates, oxides, carbides) while inorganic chemistry deals with elements and their compounds other than organic compounds; (2) examples: methane, ethanol (organic); NaCl, H₂SO₄ (inorganic). Similarity: both study the composition, properties and reactions of matter.

a) Industrial chemistry. b) Astrochemistry. c) Polymer chemistry.

a) Analytical chemistry. b) Physical chemistry. c) Inorganic chemistry (as given in the textbook).

a) Analytical chemistry (forensic chemistry). b) Geochemistry. c) Medicinal chemistry.

a) Environmental chemistry. b) Biochemistry. c) Nuclear chemistry.

The book excludes these simple carbon compounds from organic chemistry and studies them in inorganic chemistry. Examples: CaCO₃ (carbonate), CO₂ (oxide), CaC₂ (carbide), NaHCO₃ (bicarbonate).

(1) Radioisotopes are used in medicine, e.g. radiotherapy to treat cancer. (2) Nuclear reactions in power plants produce energy (electricity). (Any two suitable uses.)

Chemistry gives the knowledge of composition, properties and interaction of drugs with biological targets. A doctor who knows this can understand how a medicine acts in the body, what dose is safe and what side effects it may cause.

Forensic chemistry examines physical traces such as body fluids, bones, fibres and drugs to identify an unknown compound. It is an application of analytical chemistry.

Biochemistry: chemistry + biology. Geochemistry: chemistry + geology (earth science). Astrochemistry: chemistry + astronomy. Medicinal chemistry: chemistry + medicine/biology. (Any four.)

Sedimentation, filtration and disinfection are used to remove solids and harmful microbes and protect water.

Nylon – bearings (or fibres); polyethylene – plastic bags and cups; Teflon – coating of cookware; polyester – cloth; epoxy – glue. (Any two with uses.)

It tells us the composition and distribution of elements in rocks, minerals, soils and water, which helps to find ores and minerals and to understand problems like pollution and climate change.

Astrochemistry is the branch of chemistry that studies chemical processes and reactions in astronomical environments. Places: stars, planets, comets, interstellar space (any two).

Physical chemistry uses laws and theories to understand the structure and changes of matter. Example: the working of vehicle batteries is explained by the principle of electrochemistry.

a) Fuels like petrol or natural gas (hydrocarbons), sugar, cooking oil. b) Common salt, iron, sulphuric acid. c) Working of a vehicle battery.

Industrial chemistry: large-scale production of cement. Analytical chemistry: methods and instruments that check the composition of each batch.

No. Carbonates, bicarbonates, oxides and carbides of carbon are studied in inorganic chemistry. Examples: CaCO₃ and CO₂ contain carbon but are not organic; methane and ethanol are organic.

It produces fertilisers, cement, soap, medicines and other chemicals on a large scale. This supplies daily needs, saves foreign exchange and gives employment.

Biochemistry finds out which chemical change in the body causes the disease (e.g., which enzyme is overactive). Medicinal chemistry then designs and develops a drug that attaches to this target and stops the problem.

Polymer chemists study polymers, their types, properties, uses and how monomers join (polymerisation). Example: a plastic bag (polyethylene).

Analytical methods and instruments find out which substances are present and how much. This shows whether the product meets the standard and is safe.

An essential question is an open-ended question about an important idea of a branch of chemistry. It cannot be answered by one word, so it guides thinking, study and investigation.

a) What is the structure of an atom, and how does it influence chemical behaviour? How do ionic, covalent and metallic bonds form?

b) Why is carbon considered the backbone of organic compounds? What are the major functional groups and how do they affect properties?

a) How do human activities contribute to air pollution, and what are the consequences for the environment? (or: What role do greenhouse gases play in climate change?)

b) How do nuclear reactions differ from chemical reactions? (or: What is the role of radioisotopes in medicine?)

Question: How can we accurately determine the chemical composition of a sample? Analytical chemistry answers it by methods and instruments (for example titration or spectroscopy) that identify and measure the substances present.

a) How do biomolecules such as carbohydrates, proteins, nucleic acids and lipids contribute to the structure and function of living organisms?

b) What are polymers, and how do their structures affect their properties?

Geochemistry: How do geological processes influence the distribution of elements in the Earth's crust? Astrochemistry: What types of reactions occur in astronomical environments? The first is about the Earth, the second about space.

Essential question: How can we accurately determine the amount of sugar in a sample of juice? Branch: analytical chemistry.

a) How are drugs designed and developed for specific therapeutic targets?

b) How does the periodic table help to organise elements? (or: What distinguishes inorganic compounds from organic compounds?)

(b) is better. It is open-ended and needs explanation of the link between structure and properties, whereas (a) can be answered with a short definition.

1) What are polymers, and how do their structures affect their properties (why do plastics last long)? – polymer chemistry. 2) How do human activities contribute to pollution, and what are the consequences for the environment (what does plastic waste do to soil and water)? – environmental chemistry.

1) How can we accurately determine which substances are present in a water sample? – analytical chemistry. 2) How do human activities cause water pollution and how can it be reduced (e.g., by sedimentation, filtration, disinfection)? – environmental chemistry.

How do nuclear reactions differ from chemical reactions, and what are their applications? What is the role of radioisotopes in medicine?

Branch: nuclear chemistry. Essential question: What is the role of radioisotopes in medicine, and how do nuclear changes differ from chemical changes?

Chemistry is the study of matter, its properties, composition and interactions with other matter and energy. It can also be seen as the study of Earth (solids), Air (gases), Sea (liquids) and Sky (plasma) and how they interact.

States of matter in interactions: solids (Earth) such as rocks and minerals react with gases of the air, e.g. iron rusting with oxygen; liquids (sea water) dissolve solids and gases, e.g. salts and CO₂ dissolving in sea water; gases (air) take part in processes such as combustion and photosynthesis; plasma (sky, e.g. the Sun and lightning) provides energy and causes reactions such as the formation of nitrogen oxides. These four states constantly interact with each other.

1) Organic chemistry – carbon compounds; example: fuels like petrol. 2) Inorganic chemistry – elements and their compounds except organic ones; example: Li-ion batteries. 3) Physical chemistry – laws and theories for structure and changes of matter; example: vehicle batteries. 4) Analytical chemistry – methods and instruments to find composition; example: forensic examination of drugs. 5) Biochemistry – changes in living organisms; example: digestion of starch. 6) Environmental chemistry – pollutants and their effects; example: purification of water by filtration and disinfection.

Geochemistry studies the composition, distribution and transformation of elements and compounds in rocks, minerals, soils, water and the atmosphere. It shows how pollutants move through soil and water, how elements are stored and released in the crust and atmosphere, and how gases from the Earth affect the atmosphere. This knowledge helps to control pollution and to understand and reduce climate change.

Example: Analytical – how can we accurately determine the composition of a sample? (needed for quality and safety); how are analytical methods used to identify and quantify substances? Environmental – how do human activities cause air pollution? (to protect health); what role do greenhouse gases play in climate change? Nuclear – how do nuclear reactions differ from chemical reactions? (to use nuclear energy safely); what is the role of radioisotopes in medicine? (diagnosis and treatment).

Nuclear chemistry deals with changes in atomic nuclei. Uses: radiotherapy and diagnosis by radioisotopes; energy production in nuclear power plants. Astrochemistry deals with chemical processes and reactions in stars, planets, comets and interstellar space. Areas: molecules in the tails of comets; chemical reactions in gas clouds of space.