GENERAL SCIENCE (Chemistry)

 Fundamentals 

• Organic Chemistry - Carbon in combination with mainly hydrogen, oxygen, nitrogen.  Example - natural products,  carbohydrates,  steroids, protein. 

• Inorganic Chemistry - all elements & compounds not covered in Organic Chemistry. Example  - minerals,  salts,  Inorganic polymers. 

• Physical Chemistry  - mathematical & physical description of organic & inorganic compounds and reactions. Example  - Electrochemistry,  Chemical Thermodynamics,  Photochemistry. 

• Biochemistry  - Chemistry of biological systems.  Example  - Enzymes,  Biosynthesis. 

Matter 

• Matter is anything that occupies space and has mass. In other words, matter has mass and volume. 
• Theory of matter is made up small particles i.e. atoms, put forward by John Dalton.

1. Physical Classification:- Solid, Liquid,  Gas (Elements & Compounds)
2. Chemical Classification:- Homogeneous,  Heterogeneous (Mixtures)

• Homogeneous Mixture - uniform composition throughout its mass and no visible boundaries of separation between various constituents. 

• Heterogeneous Mixture - different composition throughout its mass and visible boundaries of separation between various constituents.  

States of Matter 

Solid	Liquid	Gas
Rigid	Not rigid	Not rigid
Fixed shape	No fixed shape	No fixed shape
Fixed volume	Fixed volume	No fixed volume
Can't be compressed	Can't be compressed	Can be compressed

• Gases are highly compressible as compared to Solids and Liquids. So, Liquefied Petroleum Gas (LPG) used in our households for cooking food.

👉 Atmosphere is a unit to measure the pressure exerted by gas. 

           1 atmosphere = 1.01 × 10⁵ Pascal(Pa)
       The pressure of air in the atmosphere is called atmospheric pressure. 

• The atmospheric pressure at sea level is 1 atmosphere and is taken as normal atmospheric pressure.

• As we go upwards,  pressure of air above us reduces. 

Plasma

• Plasma is considered as fourth state of matter.

• Consists of particles in the form of ionised (positively or negatively charged) gases. 

• As Plasma is formed at high temperature,  it is usually very hot.

• Stars / Sun are mostly made of Plasma,  which makes them glow. 

• Fluorescent tubes and Neon Signboards consist of Plasma. The gas present in them gets ionised, when electricity flows,  which makes them glow.

• Colour of Plasma depends on nature of gas.

• Fluorescent tubes are usually filled with Helium and Neon Signboards are filled with Neon gas.

Physical Change - 

• changes such as change in temperature, shape,  colour or similar features,  but no change in the internal or chemical composition of substances. 
• Can easily be reversed. 
• Very little heat or light is absorbed or given out.
• Ex:- Crystallisation, Sublimation,boiling, dissolving of sugar or salt, etc.

Chemical Change -

• Change in internal or chemical composition of substances. 
• Can't be reversed at all or require very large amount of energy to be reversed. 
• a lot of heat or light energy is absorbed or given out.
• Ex:- digestion of food, milk going sour, various metabolic reactions,  chemical battery usage, electroplating of a metal.

👉 Products obtained through chemical processes are pure in nature. 

Radioactivity 

• Radioactivity :- It is the spontaneous release of energy from unstable nuclei in terms of electromagnetic rays and emission of particles.

• Discovered by Henry de-Becqueral.

• Unit - Becqureal 

• This property is also known as Uranium Radioactivity, due to Uranium mineral gaveoff invisible radiation. 

• Later Pierre Curie & Madam Curie showed similar phenomena in other metals like Radium, Francium and Poeonium.
• Radioactivity is exhibited by elements of high atomic weights where nuclei are unstable & break up of their own accord. 
• Rutherford studied the effect of electric ans magnetic fields on the radioactive rays emitted by different radioactive substances. 

Subatomic Particles 

1. ɑ - particles 

• a positively charged Helium (He) atom, which has very little penetrating power. 
• can be absorbed by a sheet of paper or stopped by Al foil.
• With the emission of an ɑ - particle, atomic number decreases by 2 and mass number decreases by 4.
• Causes burns on human body.
• Produce fluorescence in substances 
• Deflected by electric and magnetic fields.

2. 𝜷 - particles 

• A negatively charged light particle.
• Penetrating power is greater than ɑ - particle.
• Rays are deflected towards +ve plate.
• With the emission of an 𝜷 - particle, atomic number decreases by 1 and mass number doesn'tchange.
• Produce fluorescence in substances
• Deflected by electric and magnetic fields
• Produce artificial radioactivity 

3. 𝞬 - particles 

• are electromagnetic radiations of low wavelength, high frequency and move with high velocity 
• Highly penetrating power
• Used in radiotherapy 
• Not deflected by electric and magnetic fields
• Produce fluorescence in substances

Fluorescence 

• There are certain substances which, on being illuminated by high frequency light,  emit light of relatively low frequency. 
• The emission occurs so long the substance is being illuminated. This phenomenon of emission of light is called fluorescence. 

Nuclear Reaction 

• Here a nucleus bombarded with an elementary particle (like neutron, proton, etc.) or with another to produce other products in a very short time span. 
• 1st nuclear reaction was discovered by Rutherford in 1919 when he bombarded neutron with ɑ - particles .

Nuclear Fission 

• A nuclear reaction in which nucleus splits into two nuclei of nearly equal mass.
• Atom bomb is based on nuclear fission. 

Nuclear Fusion 

• A nuclear reaction in which one or more light nuclei combined together to form a heavier nucleus.
• Hydrogen bomb is based on nuclear fusion.
• High temperature i.e 10⁸K and high pressure is required 

👉 Hydrogen bomb is 1000 times powerful than atombomb.

👉 Penetrating power of neutrons is very high and it can penetrate through the nucleus of an atom. Hence, neutron is responsible for the nuclear fission. 

Cement

• Raw materials - Lime Stone & Clay

• In  Cement,  Lime is present in combined state as Calcium Silicates and Calcium Aluminates.

• Cement containing excess amount of Lime - cracks during setting 

• Cement containing less amount of Lime - weak in strength 

• A small amount of gypsum is added to slow down the setting of Cement. 

• Cement with excess of Silica - slow setting 

• Cement with excess of Alumina - quick setting 

• Cement containing no iron is white, but hard to burn.

• Setting of Cement is an exothermic process.

NOTE

1. Endothermic Reaction - Reaction occurring with absorb of energy.

     A + B →C −  ΔE

     Ex.- Digestion 

2. Exothermic Reaction - Reaction occurring with release of energy. 

      A + B →C + ΔE

Ex.- Respiration,  Decomposition