NCERT Class 7 Science — Chapter 2: Physical and chemical changes

Which of the following statements correctly describes the process of Crystallisation?

In the reaction between Copper Sulphate solution and Iron, the resulting green colour is due to the formation of:

Which of the following is NOT a characteristic indicator that a chemical change has taken place?

Consider the following phenomena: 1. Photosynthesis 2. Digestion of food 3. Fermentation of grapes 4. Ripening of fruits Which of the above are classified as chemical changes?

During the crystallization of copper sulphate, dilute sulphuric acid is added to water primarily to:

When carbon dioxide is passed through lime water, it turns milky due to the formation of:

With reference to the reaction between Copper Sulphate and Iron, consider the following statements: 1. The colour of the solution changes from blue to green. 2. The green colour is due to the formation of Copper Oxide. 3. A brown deposit forms on the iron object, which is Rust (Iron Oxide). Which of the statements given above is/are correct?

With reference to the ozone layer, consider the following statements: 1. Ozone absorbs ultraviolet radiation from the sun. 2. The breakdown of ozone into oxygen is a physical change. 3. Ozone is an allotrope of oxygen. Which of the statements given above is/are correct?

When the ash obtained from burning magnesium is dissolved in water, the resulting solution is:

Which of the following changes involves the absorption of radiation?

With reference to the burning of a magnesium ribbon, consider the following statements: 1. It burns with a dull blue flame. 2. The ash formed is chemically different from the magnesium ribbon. 3. The reaction produces a new substance called magnesium oxide. Which of the statements given above is/are correct?

With reference to the "Lime Water Test", consider the following statements: 1. It is a standard test for Carbon Dioxide gas. 2. The milky appearance is due to the formation of Calcium Oxide. 3. The chemical name of lime water is Calcium Hydroxide. Which of the statements given above is/are correct?

With reference to the rusting of iron, consider the following statements: 1. Rust is chemically the same substance as iron. 2. The presence of both oxygen and water (or water vapour) is essential for rusting. 3. High humidity increases the rate of rusting. Which of the statements given above is/are correct?

Match List I with List II and select the correct answer using the code given below: List I | List II A. Baking Soda | 1. Iron Oxide B. Vinegar | 2. Acetic Acid C. Lime Water | 3. Sodium Hydrogencarbonate D. Rust | 4. Calcium Hydroxide

Consider the following statements about the burning of coal: 1. It is a physical change because coal only changes its state. 2. It is a chemical change because heat is produced. 3. It is a chemical change because new substances like carbon dioxide are formed. Which of the statements given above is/are correct?

Consider the following statements regarding Liquified Petroleum Gas (LPG): 1. When it comes out of the cylinder, it changes from liquid to gas. 2. The burning of LPG is a physical change that produces heat. 3. The change from liquid to gas is a chemical change. Which of the statements given above is/are correct?

Why is it advised not to stare at burning magnesium ribbon for prolonged periods?

On what basis is the setting of curd from milk classified as a chemical change?

Consider the following statements regarding the prevention of rusting: 1. Applying a coat of paint or grease prevents contact with air and moisture. 2. Galvanisation is the deposition of a layer of chromium on iron. 3. Stainless steel resists rusting. Which of the statements given above is/are correct?

Consider the following statements regarding the "Ozone Layer": 1. It acts as a natural shield against infrared radiation. 2. It absorbs ultraviolet radiation and breaks down into oxygen. Which of the statements given above is/are correct?

Consider the following statements about Stainless Steel: 1. It contains Iron. 2. It contains Carbon. 3. It contains Chromium, Nickel, and Manganese. 4. It rusts easily in moist air. Which of the statements given above are correct?

What is the chemical nature of the solution formed when Magnesium Oxide is dissolved in water?

"Blue Vitriol" is the common commercial name for which of the following chemical substances?

Stainless steel is made by mixing iron with carbon and which of the following metals?

The process of 'Galvanisation' involves the coating of iron with which one of the following metals?

Anaerobic bacteria digest animal waste to produce biogas, which is subsequently burnt as fuel. How are these two processes classified?

Why do ships suffer a lot of damage from rusting despite being painted? 1. The entire hull of the ship remains above water level. 2. Water drops cling to the outer surface above water. 3. Sea water contains salts which slow down the process of rust formation. Select the correct answer using the code below:

Which of the following pairs is correctly matched regarding the reaction of Copper Sulphate with Iron?

When baking soda is mixed with lemon juice, bubbles are formed. This is due to the evolution of: