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In this article, you will get the NCERT solutions to Class 9 Science Chapter 1 - Matter in Our Surroundings. All these solutions are available in PDF format which you may download without paying any charge. Our subject experts have reviewed these NCERT solutions to provide you the error-free content which will make it easy for you to make an effective preparation for the annual exams.
Some of the questions and their solutions from NCERT Solutions for Class 9: Matter in Our Surroundings, are as follows:
Q. Give reasons for the following observation:
The smell of hot sizzling food reaches you several meters away, but to get the smell from cold food you have to go close.
Ans. Evaporation is directly proportional to temperature, means hot food evaporates easily.
Diffusion of hot food vapors with air becomes very fast and can reach to a distant place within a very short time.
Q. Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why
Ans. Liquids have lower density than that of solids. Water is also a liquid so it should also have less density than that of solid that is ice.
But the case is not so and the reason for the same is the cage-like structure of ice. i.e., presence of vacant spaces between water (H2O) molecules when they linked in ice. The number of these spaces is comparatively less in water. Being more porous than water, ice is lighter than water and floats over the surface of water.
Q. For any substance, why does the temperature remain constant during the change of state?
Ans. During the change of state of a substance, the temperature remains constant. This can be understood with the help of an example. When a solid is heated to its melting point, the temperature first rises and becomes constant when reaches its melting point. Now, on further heating, the heat energy provided to the substance helps to break the attraction force between the solid molecules. This heat is called latent heat. That is why, the temperature does not rise.
Q. Why are we able to sip hot tea or milk faster from a saucer rather than a cup?
Ans. A liquid has large surface area in a saucer than in a cup. Thus, it evaporates faster and cools faster in a saucer than in a cup. For this reason we able to sip hot tea or milk faster from a saucer rather than a cup.
Q. Convert the following temperatures to the Kelvin scale.
Ans. To convert temperature from Celsius to Kelvin scale, add 273 to the given values because:
° C + 273 = K
(a) 25°C + 273 = 298 K
(b) 373°C + 273 = 646 K
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