Unit-1 Nature of Science in Chemistry
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Unit-1 Nature of Science in Chemistry
Answer: Chemistry studies the composition, structure and properties of matter and the physical and chemical changes it undergoes.
Answer: Physical chemistry applies physical laws and theories, such as thermodynamics and kinetics, to study chemical systems.
Answer: The composition of the salt-water mixture can be varied and its components keep their identities, so it is a homogeneous mixture and not a compound.
Answer: Matter is defined as anything that has mass and occupies space, for example air, water and books.
Answer: Flammability describes how a substance reacts to burn and form new substances, so it is a chemical property; colour, melting point and density are physical properties.
Answer: Organic chemistry is the branch that studies compounds of carbon, which occur in living things and in many synthetic substances.
Answer: Analytical chemistry is concerned with determining what substances are present (qualitative) and how much is present (quantitative).
Answer: Mass is conserved in a chemical reaction, so 12 g + 32 g = 44 g of carbon dioxide is produced.
Answer: Kinetic energy is the energy a body has because it is in motion.
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Answer: A chemical change produces new substances having different properties, whereas a physical change does not form new substances.
Answer: Inorganic chemistry is the study of elements and their compounds generally excluding organic (carbon) compounds.
Answer: Industrial chemistry deals with the large-scale production of chemicals and materials used in daily life.
Answer: In water (H2O), 2 parts by mass of hydrogen combine with 16 parts by mass of oxygen, so the fixed mass ratio is 1 : 8.
Answer: Melting of ice only changes the state of water from solid to liquid; no new substance is formed.
Answer: Natural gas is mainly composed of methane (CH4), which is used as a fuel.
Answer: Rusting forms a new substance (rust) from iron, oxygen and moisture, so it is a chemical change.
Answer: Green chemistry designs chemical processes that reduce or eliminate the use and production of hazardous substances.
Answer: Water always contains hydrogen and oxygen in a fixed ratio and has properties completely different from its elements, so it is a compound.
Answer: Combustion is the reaction of a substance with oxygen, so oxygen is necessary for burning.
Answer: Electrolysis of water splits it into hydrogen and oxygen gases using an electric current.