CBSE ADDA

Clasa 9 Science !  Here's a multiple-choice quiz based on chapter Atoms and Molecules chemistry class 9 🎈Topic  🎈Dalton's Atomic Theory: 1. Who is credited with the development of Dalton's Atomic Theory?    a) John Dalton    b) Albert Einstein    c) Isaac Newton    d) Marie Curie 2. According to Dalton's Atomic Theory, atoms are:    a) Indivisible    b) Composed of protons, neutrons, and electrons    c) Made up of smaller particles called quarks    d) Always in a state of motion 3. Dalton's Atomic Theory states that all atoms of a given element are:    a) Identical    b) Different in size and mass    c) Different in chemical properties    d) Composed of protons and electrons 4. In Dalton's Atomic Theory, compounds are formed by:    a) Mixing atoms of different elements together    b) Breaking atoms into smaller particles    c) Combining atoms in simple, whole-number ratios    d) Randomly arranging atoms 5. Which part of Dalton's Atomic Theory w

Gravitational and buoyancy force class 9 physics (science Book) Gravitation and the universal law of gravitation. The motion of objects under the influence of gravitational force on the earth. The weight of a body varies from place to place. Conditions for objects to float in liquids. 1.When we move from the poles to the equator. Hence, the value of ‘ g ’ decreases. Why Ans: The shape of earth is an ellipse so when we move from the poles to the equator the radius of the earth R increases.  Hence, the value of ‘ g ’ decreases because value 'g' is inversely proportional to the radius of earth. g = GM/R^2 2. How does the force of gravitation between two objects change when the distance between them is reduced to half? Answer: when the distance between the objects is reduced to half the gravitational force increases by four times the original force. 3.. The gravitational force acts on all objects in proportion to their masses. Why, then, a heavy object does not fall faster than a

Class 09 Atoms and Molecules Numerical Problem based on Law of chemical Combination Law of conservation of mass Law of constant proportion Empirical formula 1. If 10 grams of CaCO 3 on heating gave 4.4g of CO 2 and 5.6g of CaO, show that these observations are in agreement with the law of conservation of mass.(Based on Law of conservation of mass) Solution:  Mass of the reactants = 10g ;  Mass of the products = 4.4 + 6.6g = 10g Since the mass of the reactants is equal to the mass of the products, the observations are in agreement with the law of conservation of mass. 2. 1.375 g of cupric oxide was reduced by heating and the weight of copper that remained was 1.098g.  In another experiment 1.179 g of copper was dissolved in nitric acid and the resulting copper nitrate was converted into cupric oxide by ignition . The weight of cupric oxide formed was 1.476 g. which law of chemical combinations does this data state? Solution: in first experiment: Copper oxide = 1.375g ;   Coppe

Matter in our surrounding solved questions Q. 1. What is a matter? Answer: Anything that occupies space and has mass is called a matter.  For example:- Chalk, Milk, Sugar etc. Q. 2. Sodium chloride and sugar have same appearance. Are they same or different? Answer:  They have different physical and chemical properties. So, they are different Q. 3. All substances around us are alike. How? Answer:  All substances can occupy space and have weight. Q. 4. How can we say that air is a matter? Answer:  Air occupies space and have weight. Hence air is a matter. Q. 5. State the characteristics of matter? Matter has mass, weight and occupies space. Q. 6. What are the intensive properties of matter? Answer:  Density, colour, melting point, boiling point, refractive index etc. are the intensive properties of  matter as it does not depend upon the amount of matter contained in it Q. 7. What are the extensive properties of matter? Answer:  The properti

1. Q. The description of atomic particles of two elements X and Y is given below Protons neutrons electrons X 8 8 8 Y 8 9 8 (i) What is the atomic number of Y? (ii) What is the mass number of X? (iii) What is the relation between X and Y? (iv) Which element/elements do they represent? (v) Write the electronic configuration of X? (vi) Write the cation/anion formed by the element Ans: (i) Atomic number of y =  8             (ii) Mass number of x – 16           (iii) x and y are isotopes   (iv) x and y represent – oxygen               (v) 2, 6                                       (vi) It will form an anion – O -2 2. Q. Which of the following are isotopes and which are isobars? Argon,  Protium, Calcium, Deuterium. Explain why the isotopes have similar chemical properties but they differ in physical properties? Ans: Isotopes – Protiu