What is Chemistry?
Chemistry is the scientific discipline that explores the composition, structure, and properties of matter,
as well as the transformations it undergoes. It encompasses various branches, including physical
chemistry, organic chemistry, inorganic chemistry, biochemistry, and analytical chemistry.
Branches of Chemistry
Physical chemistry applies the principles of physics to the study of chemical reactions and properties.
Organic chemistry focuses on carbon-based compounds, while inorganic chemistry examines non-
carbon compounds. Biochemistry investigates living organisms, and analytical chemistry identifies the
substances present in materials and their amounts.
Measurement System
,The metric system is a collection of compatible units used to measure quantities such as length, mass, or
volume. The International System of Units (SI) is the official metric system. The system uses prefixes like
nano- (billionth), micro- (millionth), milli- (thousandth), centi- (hundredth), kilo- (thousand), and mega-
(million) to denote different units.
Physical Quantities
Mass measures the quantity of matter in an object, whereas weight measures the force of gravity acting
on it. Density is calculated by dividing mass by volume.
Temperature and Time
, Celsius is a temperature scale where 0°C is the freezing point of water and 100°C is the boiling point.
Absolute zero is the lowest possible temperature, at -273.15°C. Kelvin is another temperature scale
where 0 K is absolute zero.
Precision and Accuracy
Precision refers to the consistency or reproducibility of an experiment. Accuracy measures how close a
measurement is to its actual value. Significant figures are all certain digits in a measurement, plus one
uncertain digit.
States of Matter
Matter can exist in three states: solid (definite shape and volume), liquid (definite volume but not
shape), and gas (neither shape nor volume).