Chapter 15: Our Environment Introduction The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land) and all organisms such as plants, animals, human beings, and micro-organisms like bacteria and fungi (called decomposers). Waste materials produced by human and animal activities are poisonous to some extent and can be divided into: Biodegradable … Read more
14. SOURCES OF ENERGY Characteristics of a good fuel: High calorific value Less smoke Less residue after burning Easy availability Inexpensive Easy to store and transport Fossil fuels: Were formed millions of years ago, when plants and animal remains got buried under the earth and were subjected to high temperature and pressure conditions. E.g.: Coal, … Read more
Chapter 13: Magnetic Effects of Electric Current Magnet Attracts iron, cobalt & nickel. Freely suspended magnet aligns in North-South direction. Uses of Magnets Radio & stereo speakers Refrigerator doors Audio & video cassette players Computer hard disks & floppies Children’s toys Magnetic Field & Field Lines The region around a magnet where magnetic force is … Read more
Electricity 1. Positive and Negative Charges Definition: The charge acquired by a glass rod when rubbed with silk is called positive charge, while the charge acquired by an ebonite rod when rubbed with wool is called negative charge. 2. Coulomb (C) SI Unit of Charge: One coulomb is defined as the amount of charge that … Read more
The Human Eye and the Colourful World 1. The Human Eye The human eye is a natural optical instrument used for vision. It functions similarly to a camera with a lens and screen system. Retina: Light-sensitive screen inside the eye where the image is formed, containing rods and cones. Cornea: Thin membrane covering the eyeball, … Read more
Light: Reflection and Refraction 1. Ray of Light A line drawn in the direction of propagation of light is called a ray of light. 2. Beam of Light A group of rays of light emitted by a source of light is called a beam of light. A light beam is of three types: Parallel beam: … Read more
Heredity and Evolution 1. Heredity The transmission of characters from parent to their offspring is known as heredity. The study of heredity and variations is known as genetics. Clones are organisms that are carbon copies of one another. Variation in sexually reproducing organisms is caused due to factors like environment, crossing over, recombination of genes, … Read more
Control and Coordination Animals- Nervous System: Nervous system is the organ system present in the animals to control and coordinate different activities of the body. Nervous system comprises of the brain, the spinal cord, and a huge network of nerves that are spread throughout the body. The nervous system is responsible for sending, receiving and … Read more
Chapter 6: Life Processes Life Processes The processes that are necessary for an organism to stay alive. Eg. Nutrition, respiration, etc. Criteria of Life Growth Movement Nutrition The process in which an organism takes in food, utilizes it to get energy, for growth, repair and maintenance, etc. and excretes the waste materials from the body. … Read more
Periodic Classification of Elements 1. Introduction to Classification Classification is an essential concept in science that involves identifying and grouping similar elements based on their properties. The periodic classification of elements has evolved over time as new elements were discovered and scientific understanding improved. 2. Lavoisier’s Classification Lavoisier, a French chemist, classified elements into two … Read more