Measurements

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1.general physics  1.1 length and time  -i-Physical Quantity Physical Quantities A physical quantity is a property of an object that can be measured with a measuring instrument. A physical quantity is usually expressed as “a magnitude ( numerical value)  and a  physical unit or more ” Example :- Normal body temperature of a healthy human being is  37  0 C -ii-Length Measuring Length. Length is “the distance between two points in a space”. According to SI units, the length quantity is expressed in meter. There are several kinds of measuring devices used to measure quantity of length, among others, are as follows. Tools used… a-   Measuring tape. b-   Ruler c-   Vernier callipers. d-    Micrometer Measurement of length Length is measured accurately through many meth...
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States of matter

States of matter

Molecular model

Interpret the temperature of a gas in terms of the motion of its ​molecules.

The higher the temperature, the faster the speed of the molecules.

Temperature is a measure of the average speed of the molecules.

Temperature is how hot something is; heat is energy that flows from hot ​substances to cold substances.


Describe qualitatively the pressure of a gas in terms of the motion ​of its molecules.


At a constant temperature, gas molecules move at a constant average speed, ​so that the force of the collision is the same ( on average ).

If the gas is compressed into a smaller volume, there are more frequent ​collisions on each unit of area, so that the total force per unit area ​increases and the pressure increases.

If a gas expands to a greater volume at a constant temperature, the pressure ​decreases.


If you look at smoke through a microscope, you will see the particles move in a zigzag motion. This is known as Brownian motion. The smoke particles have very little mass but are larger enough to be seen. They collide with the air particles randomly and move in different directions, to give a random motion. 







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