Table of Contents

9th Physics chapter 7 Long questions

9th Physics chapter 7 Long questions. We will solve only 9th class physics revised smart syllabus long questions.

7.1 Describe the main points of particle theory of matter which differentiate solids, liquids and gases.

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7.2 What is temperature? How is it measured? Describe briefly the construction of a mercury-in-glass thermometer.

Temperature of a body is defined as the degree of hotness or coldness.

For the exact measurement of temperature, we require an instrument called thermometer.

Expansion in the volume of a liquid can be used for measurement. This is known as liquid-in-glass thermometer. Mercury is commonly used.

Mercury-in-glass thermometer is made of glass. It has bulb at one end filled with mercury. When the temperature rises, Mercury expands and moves up through the narrow capillary tube in the form of a mercury thread. The position of the end of the thread reads the temperature.

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7.3 Compare the three scales used for measuring temperature.

The three commonly used temperature scales are Celsius, Fahrenheit and Kelvin.

In Celsius or Centigrade scale, the numerical value assigned to lower and upper fixed points are 0 and 100 respectively. As the difference between these values is 100, so the space between these points is divided into 100 equal parts. each part is known as 1 degree centigrade.

In Fahrenheit scale, the numerical value assigned to lower and upper fixed points are 32 and 212 respectively. As the difference between these values is 180, so the space between these points is divided into 180 equal parts. each part is known as 1 degree Fahrenheit.

In Kelvin scale or Absolute temperature scale, the numerical value assigned to lower and upper fixed points are 273 and 373 respectively. As the difference between these values is 100, so the space between these points is divided into 100 equal parts. each part is known as 1 Kelvin.

Conversion of Celsius to Fahrenheit and Fahrenheit to Celsius:-

$$T_f=\frac95\times T_c+32\\T_c=\frac59(T_f-32)$$

Relationship between Kelvin and Celsius:-

$$T_k=T_c+273$$

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