UNIT 1- SOME BASIC CONCEPTS OF CHEMISTRY

Day 3
17.4.20

Good morning Boys,
Today we will start with our first unit ,some basic concepts of chemistry.
Students are required to make one chemistry register where all the work related to the subject need to be noted. Register will be evaluated when the school reopens. 

LEARNING OBJECTIVE :
students will be able

• Recall the S.I Units of Measurements
• Define matter
• Differentiate solid ,liquid and gases

   Matter
Anything that has mass and occupies space is termed as matter.example:- notebook, pencil, air, water etc
Physical Classification of Matter

• Properties	Solid	Liquid	Gas
  1. volume	Definite	Definite	Indefinite
  2. Shape	Definite	Indefinite	Indefinite
  3.  Inter  molecular force of attraction	Very high	Moderate	Negligible  /  Very low
  4.  arrangement  of molecules	Orderly arranged	Free      to      move within the volume	Free to move every where
  5.  Inter  molecular space	Very small	Slightly greater	Very great
  7. Compressibility	Not compressible	Not compressible	Highly compressible
  8.    Expansion   on heating	Very little	Very little	Highly expand
  9. Rigidity	Very rigid	Not  rigid  knownas fluid	Not      rigid      and known as fluid
  9. Fluidity	Can’t flow	Can flow	Can flow
  10. Diffusion	They   can   diffuse due  to  kinetic energy of liquid/gases	Can   diffuse   And rate of diffusion is very fast	Can   diffuse   And rate of diffusion is very fast

  Chemical Classification of matter---

  

Pure Substances

• Pure substances have fixed composition, the constituents of pure substances cannot be separated by simple physical methods.
  • Pure substances are further classified into elements and compounds.
• An element consists of only one type of particles. These particles may be atoms or molecules.
• For example: - Sodium (Na), copper (Cu). They contain only one type of atoms.

When two or more atoms of different elements combine, the molecule of a compound is obtained.
For example: - Water (H20), Ammonia (NH3).

Representation of atoms and molecules

• The properties of a compound are different from those of its constituent elements.

• Constituents of a compound cannot be separated into simpler substances by physical methods. They can be separated by chemical methods.

• A mixture contains two or more substances present in it in any ratio. Example:-Air
• mixture can be homogeneous or heterogeneous.
•  homogeneous mixture, the components completely mix with each other and its composition is uniform throughout.
• For example: - Air, Sugar solution.
•  heterogeneous mixtures,the composition is not uniform throughout and sometimes the different components can be observed ex sand m ixed with salt.
• The components of a mixture can be separated by using physical methods such as simple hand picking, filtration, crystallisation, distillation etc.
• Refer to the link for classification of matter :
• https://youtu.be/lUfNZ8tCTQc
• The International System of Units (SI)

 Note:

• Mass is defined as the amount of matter present in a substance.
• Weight is defined as the force exerted by the gravity on an object.
• Density of a substance is its amount of mass per unit volume. SI unit of density = kg/m3.
• Temperature There are three common scales to measure temperature — °C (degree Celsius), °F (degree Fahrenheit) and K (kelvin).  K is the SI unit.
• The temperatures on two scales are related to each other by the following relationship:-
• F = (9/5) (OC) + 32
• The Kelvin scale is related to Celsius scale as follows:-
• K =OC + 273.15
• Dalton's Atomic Theory
• • All substances are made up of tiny, indivisible particles called atoms.
• • Atoms of different elements are different in all respects.
• • Atom is the smallest unit that takes part in chemical combinations.  
• •Atoms  combine  with  each  other  in  simple  whole  number  ratios  to  form compound atoms called molecules.
• •Atoms cannot be created, divided or destroyed during any chemical or physical change.Atoms  of  the  same  element  are  identical  in  shape,  size,  mass  and  other properties.

Ok  boys thats all for the day, we will study about the various laws of chemical combination in the next blog.

Take care.

stay safe.