Is Matter Around Us Pure (क्या हमारे आस-पास के पदार्थ शुद्ध है) Ch(2) Practice Quiz in Hindi Part – 1 || Class 9 Science Practice Quizzes in English

Explanation: An alloy is a mixture of two or more metals, or a metal and a non-metal, that cannot be separated into their components by physical methods.  

Explanation: Burning wood involves a chemical reaction between the wood and oxygen, producing new substances like ash, carbon dioxide, and water vapor.  

Explanation: Melting butter is a physical change because it only changes the state of the substance from solid to liquid, without altering its chemical composition.  

Explanation: In a colloid, the dispersed phase is the substance that is distributed throughout the dispersion medium. It is analogous to the solute in a solution.  

Explanation: Gold is an element because it cannot be broken down into simpler substances by chemical reactions.  

Explanation: The Tyndall effect is the scattering of light as a light beam passes through a colloid. The individual suspension particles scatter and reflect light, making the beam visible.  

Explanation: Suspensions are unstable, meaning the particles will settle down over time due to gravity.  

Explanation: Colloidal particles are larger than molecules but not large enough to be seen with the naked eye. They range from 1 to 1000 nanometers in diameter.  

Explanation: The concentration of a solution is typically expressed as the amount of solute relative to the amount of solvent or solution. The methods mentioned in the text are mass by mass percentage, mass by volume percentage, and volume by volume percentage.  

Explanation: Carbon dioxide is a compound because it is composed of two elements, carbon and oxygen, chemically combined in a fixed proportion.  

Explanation: Metals are good conductors of heat and electricity.  

Explanation: The concentration of a solution can be calculated using the formula: (mass of solute / mass of solution) x 100. In this case, the mass of the solute (salt) is 20 g, and the mass of the solution is 200 g (20 g salt + 180 g water). So, the concentration is (20 g / 200 g) x 100 = 10%.  

Explanation: A heterogeneous mixture has a non-uniform composition, meaning the components are not evenly distributed. In sand and water, the sand particles are clearly distinguishable from the water.  

Explanation: A compound is formed when two or more elements chemically combine in a fixed ratio. A mixture is formed when two or more substances are combined physically, and their ratio can vary.  

Explanation: The dispersion medium is the substance in which the dispersed phase is distributed. It is analogous to the solvent in a solution.  

Explanation: A saturated solution is a solution in which the maximum amount of solute has been dissolved at a given temperature.  

Explanation: A pure substance consists of only one type of particle, either an element or a compound. A mixture contains more than one substance mixed in any proportion.  

Explanation: Milk is a colloid because it contains tiny droplets of fat dispersed throughout the water, and these droplets scatter light, exhibiting the Tyndall effect.  

Explanation: The particles in a solution are too small to scatter light, so the path of light is not visible.  

Explanation: Solutions and suspensions differ in their homogeneity, particle size, and stability. Solutions are homogeneous, have tiny particles, and are stable, while suspensions are heterogeneous, have larger particles, and are unstable.