CBSE ADDA

Gist of Lesson for Quick Revision (By JSUNIL) 1. Periodic table: The table which classifies all the known elements on the basis of their properties in such a way that elements with similar properties are grouped together. The first classification of elements was as metals and non-metals.  In 1789, Lavoisier first attempted to classify the elements into two divisions namely Metals and Non-metals This served only limited purpose mainly because of two reasons:  (i). All the elements were grouped in to these two classes only. The group containing metals was very big.  (ii)  Some elements showed properties of both-metals and non-metals and they could not be placed in any of the two classes. 2. All earlier attempts on the classification of the elements were based on their atomic weights. 3. The first attempt towards the classification of elements was made by Johann Dobereiner, a German chemist in 1829. He made sets of three elements which showed similar chemical p

Trend Setter Basic Science Publication - Bharati Bhawan Solutions Very Short Answer type Questions A1.Is light year a unit of time or distance? Define `1 light year? Ans: Light year is a unit of distance .one light year is a distance covered by light in 1 year. A2.What is the source of stars energy? Ans: The source of stars energy is nuclear fusion in which hydrogen atoms split up into helium atoms and large amount of energy is librated. A3.What gives galaxies different shapes? Name a few common shapes of galaxies. Ans: The  arrangement  of stars gives galaxies different shapes of galaxies. About 100 billians galaxies in the universe some of them are in shape of spiral, ring like or elliptical. A4.What is the big Dipper? Ans: The seven brightest stars in between the month of February and may form a shape of dipper in northern sky. This constellation  is called Big deeper or Saptarshi. A5. Why are Mercury venues, and Mars called terrestrial planets? Ans: This is because t

Animal kingdom: It consists of organisms which are eukaryotic, multicellular and heterotrophic. Their ells do not have cell-walls. Most animals are mobile. Animal kingdom classified on the basis of the following points: Arrangement of cells, body symmetry, nature of coelom, patterns of digestive, circulatory or reproductive systems KINGDOM ANIMALIA Animalia  are further classified as Non- Chordates( Porifera, Coelenterata, Platyhelminthes , Nematoda, Annelida, Arthropoda, Mollusca, Echinodermata) and Chordates { Protochordata, Vertebrata ( Pisces, Amphibians, Reptilia, Aves, Mammalia)} Non- Chordates  Porifera: Organisms of this group have holes or ‘pores’, all over the body and therefore known as sponges. They are mainly found in marine habitats Pores helps in circulating water throughout the body to bring in food oxygen and removal of waste. They are hermaphrodite i.e., eggs and sperms are produced by the same individual. Sponges reproduce asexually by f