EDUCATRIX

 Most of the substances found in nature are mixtures soil, air, sand etc. For some useful purposes separation of mixture is done in our daily life. There are different scientific methods to separate mixtures into it components. The choice of the methods of separation of components depends on the properties of the components of a mixture. Different types of separation methods are, Distillation  Fractional distillation  Separation using separating funnel  Sublimation  Centrifugation Chromatography 

 Law of reflection for a plane mirror is also applicable for spherical mirrors  Incident ray, reflected ray and normal at the point of incident are in a same plane. Angle of incidence and angle of reflection are equal in spherical mirrors  Rules of drawing ray diagram for spherical mirrors  Ray of light passing parallel to the principal axis  For concave mirror Ray of light parallel to the principle axis converges and passes through the focus of the mirror. For convex mirror Ray of light parallel to principal axis diverges from the focus of the mirror. Ray of light passing through the focus of the mirror  For concave mirror Ray of light passing through the focus of mirror reflects and passes parallel to the principal axis. For convex mirror Ray of light passing through the focus of mirror reflects and passes parallel to the principal axis. Ray of light incident obliquely at the poles For both concave and convex mirrors the light ray incident obliquely at the pole, reflect back to the s

 Antoine Lavoisier laid the foundation of chemical science by establishing two laws of chemical combination. ( Joseph L Proust was also a part of the experimentation that led for formulation of this laws). There are two laws of chemical combination law of conservation of mass ans law of constant proportions  Law of conservation of mass Law of conservation of mass states that mass can neither be created more be destroyed in a chemical reaction. Law of constant proportions  The law of constant proportions states that, in a chemical substance the elements are always present in a definite proportions by mass.

 When light enters from one medium to the another with different optical density, the direction of light ray changes at the point of intersection between two mediums due to refraction  When light ray enters from a denser medium to a rarer medium it bend away from the normal (as shown in figure 1). As the angle of incidence increases the refracted ray moves further away from normal.  At a particular angle of incidence, the refracted ray passes through the plane of intersection between two medium, this angle of incidence is known as critical angle (as shown in figure 2).  If the angle of incidence is greater then the critical angle, refraction doesn’t occurs and all the light rays will be reflected back to the same medium. This is known as total internal reflection 

  Ant sting contain formic acid when ants bits formic acid is injected to our body which causes inflammation, irritation and itching on skin. Since acid can be neutralised by base, so remedy for ant bites is rub the affected part with basic substances like  baking soda, calamine lotion etc so the formic acid in our skin get neutralised.

 When a ray of light pass through a colloidal fluid or suspension , the tiny particles get illuminated due to scattering. Because of this the path of the light made visible. This phenomenon is know as tyndal effect. The intensity of the scattering depends up on the size of the particles in the medium through light passes. As the size increases the intensity of the scattering also increases.   In a misty morning the path of light is visible through the areas with dense trees, because mist is a colloid of air and water vapour. Particles in the mist is big enough to scatter the sunlight so the path of the light is visible.

 There are two laws of chemical composition  Law of conservation of mass Law of constant proportions  Law of conservation of mass Law of conservation of mass state that mass can neither be created nor destroyed in a chemical reaction. Example:- 2grams of hydrogen react with 16grams of oxygen to produce 18grams of water. The total mass in the reactant and total mass in the product is same. Law of constant proportions Law of constant proportions state that in a chemical substance the elements are always present in a definite proportion by mass. Example:- in water the ratio of mass of hydrogen to the mass of oxygen is always 1:8. That means 1grams of hydrogen need 8grams of oxygen to react together and form 9gm of water. 

 A single form of matter which contain only a single type of particles is known as pure substances. Pure substances can be classified as elements and compounds Elements  An element is a basic form of matter that cannot be broken down into simpler substance by chemical reaction. Elements are divided into metals , non metals and metalloids. There are more than 100 elements known. Majority of them are solid, eleven elements are in gaseous state at room temperature and two in liquid for at room temperature mercury and bromine. Compounds A compound is a pure substance composed of two or more elements, chemically combined with one another in a fixed proportion. Composition, texture and colour of a compound is same throughout. Constituents can be separated only by chemical or electrochemical reactions.

 The rate of doing work is called as power. Also we can define power as rate of consumption of energy.  Power = energy/time(T) -(1) So electric power can be defined as rate of consumption of electric energy. Equations of electric power From joules law electrical energy produced = I²RT = VIT = V²T/R From (1) electric power (P)= I²RT/T = I²R Power (P) = I²R or P = VIT/T = VI Power (P) = VI or P= V²T/R/T = V²/R Power(P) = V²/R SI unit of power is watt(W). Since watt is very small for practical purposes we use kilowatt as unit of electric power. Commercial unit of electric energy  Electrical energy can be expressed as product of power and time Electrical energy = power  x time So commercial unit of electrical energy from the above equation can be given as kilowatt hour (kWh)

 Scattering of light is change in direction brought out by irregular and partial reflection of light when it hits on the particles of the medium. Examples of scattering of light Scattering of sunlight in the earth’s atmosphere - when sunlight passes through the earth atmosphere, ray of lights are reflected by the tiny particles of dust, smoke etc in the atmosphere  When white light is passed through one side of beaker contain colloidal sulphur (mixture of sodium thiosulphate, hydrochloric acid and water) the light emerges out through the opposite side of beaker can be observed in colours like red due to scattering of light.  Scattering and wavelength  Light is composed of seven colours VIBGOYR.  Each colours has different wavelength as shown in the above table. Colours with smallest wavelength like violet, indigo, blue etc undergo maximum scattering while interacting with the particles of medium through light passes, but colours with greater wavelength like red, orange etc scatter less

 In colloidal solutions particles are uniformly spread throughout. Due to small size of particles, colloids appears to be a homogeneous mixture but it is a heterogeneous mixture. A colloid contains a dispersion phase and a dispersion medium. Dispersed particles in colloid is known as dispersion phase and component in which dispersion phase is suspended is known as dispersion medium. Colloids are classified based on difference in state of dispersion medium and dispersion phase. Type of colloids with examples is provided in the below table, Examples of colloids  Milk, jelly, shavings cream, smoke, foam, mud etc Properties of a colloid Colloid is a heterogeneous mixture  Particles of colloid is small, cannot be seen with naked eyes  Particle size of colloids are big enough compared to pure solution to scatter a beam of light, so that we can observe Tyndall effect. ( The phenomenon in which path of a light is visible when a beam of light passed through some colloids is known as Tyndall eff