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General Science Notes – For W.B.C.S. Examination – MATTER AND ITS NATURE.
সাধারণ বিজ্ঞান নোট – WBCS পরীক্ষা – বিষয় এবং তার প্রকৃতি।
What is Matter?
Anything which has mass and occupies some space is called matter. Each and everything which we see around us is matter.Continue Reading General Science Notes – For W.B.C.S. Examination – MATTER AND ITS NATURE.
What about air? Neither we can see it nor has it mass!! Is it also matter?
The answer is yes! Air is a matter. We can’t see it but it occupies space. That is why only a limited amount of air can be filled in a balloon. Further, air has mass too. But the problem is that, its molecules move with such a high speed and the space between them is so large that we don’t feel the mass of air.
Remember when the molecules of gas collide with the wall of container they exert some force on it which is the cause of pressure of gas. Colliding molecule exerts force; this means it has some momentum. And if it has momentum, it must have mass too.
So, air is a matter.
Classification of Matter
Matter is classified at microscopic and macroscopic levels.
At microscopic level, it can be classified as solid, liquid and gas. These are the three physical states of matter.
Elements:
- The primary stuff present in all the substance is known as element, whose smallest unit is known as atom.
- Total 112 elements are known till date of which 92 are naturally occurring elements rest are results of artificial transmutation.
- There are 88 metals, 18 non metals and 6 metalloids.
- For example. Nitrogen, Hydrogen, Oxygen, Carbon etc.
Compound:
- A non elemental pure substance is called a compound in which more than one atom of elements are linked by chemical bonds formed due to chemical reaction.
- The resulting molecule is a electrically neutral particle of constant continuous composition.
- For example: Water is a compound which is formed by combination of two elements hydrogen and oxygen.
Mixture:
- Mixtures are the aggregate of more than one type of pure substance whose chemical identity remains maintained even in mixtures. Their constituent ratio may vary unlike compound.
- For example sugar syrup is mixture of water and sugar. Gun-powder contains 75 % KNO3 , 10% sulphur and 15% carbon
- There are two types of mixture (a) homogeneous (b) heterogeneous
- Homogeneous mixtures are those whose composition for each part remains constant. For example aqueous and gaseous solution.
- Heterogeneous mixtures are those whose composition may vary for each and every part. For example soil, concrete mixtures.
Physical and Chemical Properties of Matter
- Physical Property: The property which can be measured without changing the chemical composition of the substance is known as physical property like mass, volume, density, refractive index etc.
- Chemical Property: The property which can be evaluated at the cost of matter itself is known as chemical property. For example combustible nature of hydrogen gas can be verified by burning of hydrogen. The sweet taste of sugar by consuming it.
- Physical Quantities : Many physical properties of substances are quantitative in nature. Such properties are called physical properties.
- The measurement of any physical quantity consists of two parts:
- The number and
- The unit
- Accuracy of the number is expressed using concepts of significant figures
- The units of measurement are expressed in S.I. units
- The units of any physical quantity are derived using the concept of dimensional analysis.
Units for Measurement
All physical quantities have to be measured. The value of a physical quantity is expressed as the product of the numerical value and the unit in which it is expressed.
Fundamental Units:
Fundamental units are those units which can neither be derived from one another nor they can be further resolved into any other units.
The seven fundamental units of measurement in S.I. system.Quantity Name of unit Abbreviation Mass Kilogram Kg Length Meter m Temperature Kelvin K Amount of substance Mole Mol Time Second S Electric current Ampere A Luminous intensity Candela Cd
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