Notes

Introduction to Cell * Robert Hooke observed many tiny, hollow, room-like structures in a thin slice of cork through a compound microscope and called them cells. * Organisms with single cell are called unicellular organisms. * Organisms with multiple cells are called multicellular organisms. * Prokaryotes do not have nuclear membranes and membrane bound organelles. ... Read more

Atomic Models * Atoms are made of charged particles. According to Thomson’s Model:    *  An atom is a positively charged sphere with electrons set within it.    *  An atom is electrically neutral. Rutherford’s model states that:    *  There is a positively charged centre in an atom called the nucleus. Almost all the ... Read more

Atoms and Molecules * Matter is made of tiny indivisible particles. * In any chemical reaction, the total mass of the substance before and after the reaction is the same although its matter undergoes a physical change. * Molecule is the combined state of atoms. * Number of atoms constituting a molecule is atomicity. * ... Read more

Types of Substances * A change in the physical appearance but not its chemical composition is known as physical change. * A change in which a substance changes into a chemically new substance is referred to as a chemical change. * A substance which is made up of one kind of particle is referred to ... Read more

States of Matter * Solids have definite shape, volume and cannot be compressed. * Liquids flow, have definite volume and take the shape of the container.  * Gases do not have definite volume, but take the shape of the container. * Particles of matter are small in size and have space between them.  * In ... Read more