Uttar Pradesh Board Class 9 Science — Flashcards for Quick Revision

A: Matter is anything that occupies space and has mass. Examples include air we breathe, food we eat, stones, clouds, stars, plants, animals, water droplets, and sand particles. Everything in the univers

A: The Panch Tatva are five basic elements according to ancient Indian philosophers: air, earth, fire, sky, and water. They believed that everything, living or non-living, was made up of these five basic

A: When salt is dissolved in water, it disappears and spreads throughout the water without changing the water level. This shows that matter is made up of tiny particles, and the salt particles fit into t

A: A pure substance consists of a single type of particle. All constituent particles of that substance are the same in their chemical nature. It is a single form of matter with uniform composition throug

A: A mixture contains more than one pure substance. Components can be separated by physical methods. Examples: sea water (mixture of salt and water), soil (mixture of sand, clay, organic matter).

A: A homogeneous mixture has uniform composition throughout. All parts look the same and have the same properties. Example: salt dissolved in water, sugar solution, copper sulphate solution.

A: The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction. The total mass of reactants equals the total mass of products in any chemical reaction.

A: The Law of Constant Proportions states that in a chemical substance, the elements are always present in definite proportions by mass. For example, in water (H₂O), hydrogen and oxygen are always presen

A: John Dalton proposed the atomic theory. Main postulates: (1) All matter is made of tiny particles called atoms (2) Atoms are indivisible and cannot be created or destroyed (3) Atoms of same element ar