Author name: sumkhur Boro

Chapter 3: Atoms and Molecules Intext Exercise 1 Question: In a reaction, 5.3g of sodium carbonate reacted with 6g of ethanoic acid. The products were 2.2g of carbon dioxide, 0.9g water and 8.2g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.  Sodium Carbonate + ethanoic acid […]

Chapter 2: Is Matter Around Us Pure Excercise 1: Question 1: What is meant by a pure substance?Answer: The type of substance consisting of a single type of particle of the same chemical nature is called a pure substance. It can be classified as elements or compounds.Question 2: List the points of difference between homogeneous

Chapter 1: Matters In Our Surroundings Excercise 1: Question 1: Which of the following are the matter?Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.Answer: Matter is anything that occupies space and has some mass. There are three states of matter called Solid, Liquid and Gas. On the basis of these

CHAPTER 12 Exercise 12.1: Question 1: A survey conducted by an organisation for the cause of illness and death among the women between the ages 15−44 (in years) worldwide, found the following figures (in %): S. No. Causes Female Fatality rate (%) 1 Repriductive health conditions 31.8 2 Neuropsychiatric conditions 24.4 3 Injuries 12.4 4

CHAPTER 11 Exercise 11.1: Question 1: Diameter of the base of a cone is (10.5space cm) and its slant height is (10space cm). Find its curved surface area. [Assume (pi=frac{22}{7})] Answer:  We are Given the Following: The slant height ((l)) of the cone (=10space cm) The diameter of the base of cone (=10.5space cm) So,

CHAPTER 10 Exercise 10.1: Question 1: A traffic signal board, indicating ‘SCHOOL AHEAD’, is an equilateral triangle with side ‘a’. Find the area of the signal board, using Heron’s formula. If its perimeter is 180 cm, whatwill be the area of the signal board. Length of the side of traffic signal board (=a) Perimeter of

CHAPTER 9 Exercise 9.1: Question 1: Recall that two circles are congruent if they have the same radii. Prove that equal chords of congruent circles subtend equal angles at their centres.  Answer:  Given: Two given circles are congruent when they have the same radii. To Prove: Equal chords of the congruent circles subtend equal angles

CHAPTER 8 Exercise 8.1: Question 1: If the diagonals of a parallelogram are equal, then show that it is a rectangle. Answer: Given that the diagonals of aparallelogram are equal. Let us assume a parallelogram (ABCD) whose diagonals are equal as shown in the figure below. Here (ABCD) is a parallelogram, so we can write that