Matter in our surroundings

This chapter is for class 9 based on CBSE curriculum in which physical nature of matter, its characteristics are discussed along with states of matter, their inconversion, scales of temperature and difference between boiling and evaporation and factors affecting evaporation with inforgraphics and key points.

1. MATTER IN OUR SURROUNDINGS

2. Physical Nature of Matter Characteristics of Particles of Matter States of Matter Effect of Temperature and Pressure Evaporation Solids Gases Liquids Melting Point Latent Heat of Vaporisation Boiling Point Latent Heat of Fusion TOPICS TO BE COVERED

3. MATTER Matter is anything which occupies space and has mass. Cannot gain 4 electrons to form C 4- ion CLASSIFICATION OF MATTER Early Indian philosophers classified in the form of five basic elements as air, earth, fire, sky and water called Panch Tatva. On the basis of the physical state matter is classified as solids, liquids and gases. On the basis of chemical composition matter is classified as pure substances and mixtures. Pure substances may be elements or compounds. Mixtures may be homogeneous mixtures or heterogeneous mixtures. Cannot gain 4 electrons to form C 4- ion MATTER PURE SUBSTANCES MIXTURES HETEROGENEOUS MIXTURES HOMOGENEOUS MIXTURES COMPOUNDS ELEMENTS

4. PHYSICAL NATURE OF MATTER Matter is made up of particles. Matter can be broken into many pieces

5. CHARACTERISTICS OF PARTICLES OF MATTER The particles of matter are very tiny. The particles of matter have space between them. The particles of matter attract each other. The particles of matter are continuously moving.

6. Activity :- Take some water in a beaker and note its level. Dissolve some salt or sugar in it with the help of a glass rod. The salt dissolves in the water but the level of water does not change. This is because the particles of salt get into the space between the particles of water. Particles of matter have space between them

7. Activity :- Take some water in a beaker and put a drop of blue or red ink slowly along the sides of the beaker. Leave it undisturbed for a few hours. The ink spreads evenly throughout the water due to the movement of the particles of water and ink. The intermixing of two or more different types of matter on their own is called diffusion . Particles of matter are continuously moving

8. Activity :- Take an iron nail, a piece of chalk and a rubber band. Try breaking them by hammering, cutting or stretching. It is more easier to break the chalk, less easier to break the rubber band and difficult to break the iron nail. This is because the particles in the iron nail are held together with greater force than in the rubber band or chalk. Particles of matter attract each other

9. Activity :- Dissolve 2 – 3 crystals of potassium permanganate in 100ml of water in a beaker. Take 10ml of this solution and dissolve in 100ml of water. Take 10ml of this solution and dissolve in 100ml of water. Repeat this process 5 – 6 times. This shows that a few crystals of potassium permanganate can colour a large volume of water because there are millions of tiny particles in each crystal. Particles of matter are very tiny

10. STATES OF MATTER PLASMA GASES LIQUIDS SOLIDS BOSON EINSTEIN CONDENSATE (BEC)

11. STATES OF MATTER Definite shape and volume Least Kinetic energy Strong Force of attraction Least Compressible Least Fluidity Minimum Brownian motion Least Diffusion rate SOLIDS Indefinite shape but definite volume Less Kinetic energy Less Force of attraction Less Compressible Moderate Fluidity Moderate Brownian motion Moderate Diffusion rate LIQUIDS Indefinite shape and volume High Kinetic energy Least Force of attraction Highly Compressible High Fluidity High Brownian motion High Diffusion rate GASES

12. STATES OF MATTER Ionized gas Super energetic and super excited particles Unstable gaseous molecules PLASMA Super cooled gas at absolute Kelvin zero temperature BEC QUARK GLUON DEGENERATE MATTER SUPER FLUID OTHER STATES

13. TEMPERATURE AND TEMPERATURE SCALES Temperature is the degree of hotness or coldness of body. There are different scales on which temperature can be recorded. Commonly used scales are Celsius, Fahrenheit and Kelvin Relation between K & o C : o C = 273 K So, K = o C + 273 or o C = K -273 F = 9/5C + 32

14. MELTING AND BOILING When a solid is heated, the particles begin to vibrate with greater speed and begin to move more freely. Then at a particular temperature the solid melts and changes into liquid. The process of melting is also known as fusion . The temperature at which a solid melts is called its melting point . The melting point of ice is 0 C or 273 K. The amount of heat energy required to change 1kg of a solid into liquid at atmospheric pressure at its melting point is called the latent heat of fusion . When a liquid is heated, its particles begin to move even faster. Then at a particular temperature the liquid begins to boil and changes into gas (vapour). Boiling is a bulk phenomenon . The temperature at which a liquid starts boiling is called its boiling point . The boiling point of water is 100 C or 373K (273 + 100). The amount of heat energy required to change 1kg of a liquid into gas at atmospheric pressure at its boiling point is called the latent heat of vaporisation .

15. INTERCONVERSION OF STATES OF MATTER The phenomenon due to which matter changes from one state to another and then back to its original state on altering the conditions of temperature and pressure is called interconversion of states of matter. The change of state directly from solid to gas or from gas to solid is called sublimation . The change of gaseous state to liquid state on cooling is called condensation . The change of liquid state of a substance to gaseous state at boiling point is called vapourisation . The change of solid state of a substance to liquid state at melting point is called fusion .

16. EFFECT OF TEMPERATURE On increasing temperature, the kinetic energy of the particles of the matter increases and they begin to vibrate with a higher energy. Therefore, the interparticle force of attraction between the particles reduces and particles get detached from their position and begin to move freely. As a result, the state of matter begins to change. Solids undergo a phase change to form liquids. Similarly, liquids also undergo a phase change to form gases.

17. EFFECT OF PRESSURE By applying pressure, the i nterparticle spaces between particles of matter decreases. Thus, by applying pressure and reducing temperature we can convert a solid to liquid and a liquid to gas.

18. EVAPORATION The phenomenon of change of a liquid into vapors at any given temperature below its boiling point is called Evaporation . Evaporation is different than boiling. The particles of liquids have more kinetic energy. Therefore, they are able to overcome the forces of attraction and convert into vapor without any external forces.

19. FACTORS AFFECTING EVAPORATION Increase in surface area facilitates more space which helps in faster evaporation. Increase in temperature increase kinetic energy which overcome interparticle force of attraction between particles. Hence, increase in evaporation. High water content in atmosphere (Humidity) decreases rate of evaporation as less space is present to accommodate water particles in the atmosphere. High wind speed blow away water vapours allowing faster evaporation rate. SURFACE AREA WIND SPEED HUMIDITY TEMPERATURE

20. EVAPORATION CAUSES COOLING Evaporation is a surface phenomenon . The particles at the surface having high K.E. break up their force of attraction & form vapours. Since the energy is lost, that means temperature gets lowered and low temperature means cooling effect so, evaporation results in cooling effect. Cannot gain 4 electrons to form C 4- ion