"Chemistry" Chapter 01 Some basic concept of of chemistry

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   Some concept of Chemistry 

•   The branch that studies the preparation, properties, structure & reactions of material substance is called chemistry.
• Chemistry is also called the science of atoms & molecules. 

Nature of Matters :- 

Matters can exist in three physical states “solid”, “liquid” and gases.

 Particles are held very close to each other in solids.

 In Liquids, the particles are close to each other but they can move around.

 In gases, the particles are for apart as compared to those present in solid or liquid states & their

movement is easy & fast.

Different states of matter exhibit the following characteristics /-

i. Solids have definite volume & definite shape.

ii. Liquids have definite volume but do not have definite shape.

iii. Gases have neither definite volume nor definite shape.

Three states of matters are interconvetible by changing the conditions of temperature & pressure. 

Classification of Matters /-

Matters can be classified as mixture or pure substances.

 Mixtures contains particles of two or more pure substances.

For example ; Sugar solution in water, air, tea, etc are all mixtures.

 A mixtures may be homogenous or heterogenous.

 Homogeneous Mixture, the components completely mix with each other. The mixture are

uniformly distributed throughout the bulbs of the mixtures & its composition of uniform throughout.

Sugar solution & air are the example of homogeneous mixtures.

 Heterogeneous mixtures :- the composition is not uniform throughout & sometimes different

components are visible. For example, salt & sugar, grains & pulses along with some dirt (often stone

pieces).

 Pure Substances is different from mixtures. Constituent particles of pure substances have fixed

composition. Copper, Silver, Gold, Water & glucose are some examples of pure substances.

 Pure substances can further be classified into elements & compounds.

Particles of an element consists may exist as atoms & molecules.

Sodium, copper, silver, hydrogen, oxygen, etc are example of elements.

 Two or more atoms of different elements combine together in a definite ratio, the molecule of

Compound.

Example of compound are water, ammonia, CO2, sugar, etc.

 a water comprises two hydrogen atoms & one oxygen atom.

Properties of Matter and their Measurement /-

 Physical and Chemical Properties /-

These properties can be classified into two categories – “Physical Properties” such

As colour, odour, melting point, boiling point, density, etc.

“Chemical Properties” like composition, combustibility, reactivity with acids & bases, etc.

Physical Properties can be measured or observed without changing the identify or the composition of the

substances.

Chemical Properties requires a chemical change to occur.

Measurement of Physical Properties /-

Quantitative measurement of properties is required for scientific investigation.

Many properties of matter, such as length, area, volume, etc.

 Earlier, two different systems of measurement i.e, the English system and Metric System.

The International System of Units (SI) ;-

 The SI system has seven base units.

 The other physical quantities, such as speed, volume, density, etc. can be derived from these

quantities.

 The SI system allows the use of prefixes to indicate the multiples or submission of a unit.

Mass and Weight ;-

Mass of substances is the amount of matter present in it, while weight is the force exerted by gravity

on an object. Its weight may vary from one place to another due to change in gravity.

Volume ;-

Volume is the amount of space occupied by a substances. It has the units of (length)3. SI system,

volume has units of m3.

Density /-

The two properties – mass & volume.

Density = Mass / Volume

 Density of a substance is its amount of mass per unit volume.

SI unit of density = SI unit of mass / SI unit of volume

= kg / m3 or kgm-3.