Unit-1 Nature of Science in Chemistry
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Unit-1 Nature of Science in Chemistry
Answer: A hypothesis is a possible, testable explanation proposed to interpret observations.
Answer: The scientific method proceeds from observation, to hypothesis, to experiment, and then to conclusion.
Answer: In complete combustion with enough oxygen, a hydrocarbon produces carbon dioxide and water.
Answer: Alchemy is an ancient practice, not a modern branch of chemistry.
Answer: A theory is a well-supported explanation that organizes many observations and experiments.
Answer: Chemistry overlaps with physics, biology, medicine, agriculture and many other fields, so it is called the central science.
Answer: A law summarizes repeated observations that are always found to be true.
Answer: Incomplete combustion produces carbon monoxide (CO), a poisonous gas that combines with haemoglobin.
Answer: Carbon dioxide is represented by the formula CO2, one carbon atom and two oxygen atoms.
Answer: CFCs released from old refrigerators and sprays destroy ozone, thinning the protective ozone layer.
Answer: Air has mass and occupies space, so it is matter; heat, light and sound are forms of energy.
Answer: A quantitative observation involves a measurement with a number and a unit.
Answer: A blue flame shows complete combustion, in which the fuel burns fully to carbon dioxide and water.
Answer: Potential energy is stored energy due to position, such as water stored behind a dam.
Answer: A qualitative observation describes a quality without numbers, such as colour.
Answer: CNG is compressed natural gas, a clean fuel used in vehicles and homes.
Answer: The independent variable is the factor changed by the experimenter to observe its effect.
Answer: In water, hydrogen and oxygen are in the ratio 1 : 8 by mass, so 4 g of hydrogen needs 32 g of oxygen, giving 4 + 32 = 36 g of water.
Answer: The symbol of oxygen is O; O2 is the formula of its molecule.
Answer: The dependent variable is the result that depends on the changes made to the independent variable.