Question : Solutions of Questions on Page Number : 80 Q1 : Why do we classify organisms? Answer : There are a wide range of life forms (about 10 million -13 million species) around us. These life forms have existed and evolved on the Earth over millions of years ago. The huge range of these life forms makes it very difficult to study them one by one. Therefore, we look for similarities among them and classify them into different classes to study these different classes as a whole. Thus, classification makes our study easier. Q2 : Give three examples of…
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Question : Solutions of Questions on Page Number : 69 Q1 : What is a tissue? Answer : Tissue is a group of cells that are similar in structure and are organised together to perform a specific task. Q2 : What is the utility of tissues in multi-cellular organisms? Answer : In unicellular organisms, a single cell performs all the basic functions such as respiration, movement, excretion, digestion, etc. But in multicellular organisms, cells are grouped to form tissues. These tissues are specialised to carry out a particular function at a definite place in the body. For example, the muscle…
Question : Solutions of Questions on Page Number : 59 Q1 : Who discovered cells and how? Answer : Cells were discovered in 1665 by an English Botanist, Robert Hooke. He used a primitive microscope to observe cells in a cork slice. Q2 : Why is the cell called the structural and functional unit of life? Answer : Cells constitute various components of plants and animals. A cell is the smallest unit of life and is capable of all living functions. Cells are the building blocks of life. This is the reason why cells are referred to as the basic…
Question : Solutions of Questions on Page Number : 47 Q1 : What are canal rays? Answer : Canal rays are positively charged radiations. These rays consist of positively charged particles known as protons. They were discovered by Goldstein in 1886. Q2 : If an atom contains one electron and one proton, will it carry any charge or not? Answer : An electron is a negatively charged particle, whereas a proton is a positively charged particle. The magnitude of their charges is equal. Therefore, an atom containing one electron and one proton will not carry any charge. Thus, it will…
Question : Solutions of Questions on Page Number : 32 Q1 : In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass. Sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water Answer : In the given reaction, sodium carbonate reacts with ethanoic acid to produce sodium ethanoate, carbon dioxide, and water. Mass of sodium carbonate = 5.3 g (Given)…
Question : Solutions of Questions on Page Number : 15 Q1 : What is meant by a pure substance? Answer : A pure substance is the one that consists of a single type of particles, i.e., all constituent particles of the substance have the same chemical nature. Pure substances can be classified as elements or compounds. Q2 : List the points of differences between homogeneous and heterogeneous mixtures. Answer : A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example: salt in water, sugar in water, copper sulphate in water A heterogeneous mixture is a…
Question : Solutions of Questions on Page Number : 3 Q1 : Which of the following are matter? Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume. Answer : Anything that occupies space and has mass is called matter. Matter can exist in three physical states – solid, liquid, and gaseous. Chair and almond are forms of matter in the solid state. Cold drink is a liquid state of matter. Air is a gaseous state of matter. Note: The sense of smell is not matter. However, the smell or odour of a substance is classified as…
Exercise : Solutions of Questions on Page Number : 252 Q1 : What are the different ways in which water gets contaminated? Answer : Water gets contaminated by the addition of: (i) Agricultural chemicals: Farmers use excessive amounts of pesticides and fertilizers to increase crop production. These chemicals get carried away to the water bodies due to rains and floods which lead to water pollution. (ii) Industrial wastes: Industries release harmful chemical wastes into water sources, thereby polluting them. (iii) Sewage wastes: Waste materials from kitchens, toilets, and laundry sources are also responsible for contaminating water. Q2 : At an…
Exercise : Solutions of Questions on Page Number : 234 Q1 : Which of the following is NOT a member of the solar system? (a) An asteroid (b) A satellite (c) A constellation (d) A comet Answer : (c) Constellation A constellation is not a member of the solar system.Constellations are groups of stars that form recognisable shapes. Q2 : Which of the following is NOT a planet of the sun? (a) Sirius (b) Mercury (c) Saturn (d) Earth Answer : (a) Sirius Sirius is a star and not a planet of the sun. Q3 : Phases of the moon…
Exercise : Solutions of Questions on Page Number : 212 Q1 : Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room? Explain. Answer : If we are in a dark room, then it is not possible for us to see objects in the room. However, objects outside the room are visible to us. An object becomes visible when light reaches our eye after being reflected from the object. If there is no light in the room, then the objects inside the room cannot reflect any light. Hence, we…