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MATTER AND ITS PROPERTIES

MATTER AND ITS PROPERTIES

  • Matter is anything that has mass and occupies space. Mass refers to the amount of matter present in a sample.
  • Different forms of energy, such as heat, light, and electricity, are not considered to be matter.
  • Nearly all the changes that matter undergoes involve the release or absorption of energy.

Physical States of Matter

Matter exists in three physical states:

  • Gas: It has no fixed volume or shape. It takes the volume and shape of its container, i.e., it can be compressed to fit a small container and it expands to fill a large one. For e.g., oxygen, carbon dioxide and nitrogen are gases.
  • Liquid: It has definite volume but no specific shape. It assumes the shape of the portion of the container that it occupies. For e.g., water, milk, oil and alcohol are liquids.
  • Solid: It has both fixed volume and fixed shape. Neither liquids nor solids are compressible to any appreciable extent. For example, iron, wood, sugar and ice are solids.
  • The distances between the particles are minimum in solids and maximum in gases. MATTER AND ITS PROPERTIES
  • The forces of attraction between particles are strongest in solids and weakest in gases. The movement of particles is minimum in solids and maximum in gases. Solids and liquids do not get compressed when pressure is applied.
  • Gases, however, have high compressibility. By applying high pressure, they can be compressed into very small volumes.
  • Thus, a large amount of a gas can be compressed and stored in a small metal cylinder.
  • Cooking gas (Liquefied Petroleum Gas, LPG), oxygen gas supplied to hospitals in cylinders, and compressed natural gas (CNG) used as fuel for vehicles are all examples of compressed gases.

Apart from the above three basic states of matter, two other states exist, which have been recently discovered. MATTER AND ITS PROPERTIES

  • Plasma is the fourth state of matter. Inside the sun and the stars, the temperature is so high that the atoms break up to give a mixture of free electrons, and ions.
  • This mixture is called plasma, which makes the sun and other stars glow.
  • When electricity is passed through gases (at very low pressures) in a glass tube, plasma is generated. Gases present in neon sign bulbs and fluorescent tubes get ionized to form plasma when electricity is passed through them. This plasma makes them glow.
  • Bose-Einstein Condensate (BEC), the fifth state of matter, was reached by three scientists, Cornell, Ketterle and Wieman of USA, when they cooled a gas of very low density to extremely low temperatures. MATTER AND ITS PROPERTIES

Properties of Matter | MATTER AND ITS PROPERTIES

Every substance has a unique set of properties or characteristics that allow us to recognise it and to distinguish it from other substances. Properties of matter can be grouped into two categories:

  • Physical properties are those characteristics that can be observed without changing the basic identity of the substance, for example colour, odour, hardness, melting point, boiling point, and density. Examples of physical properties: Mercury is a liquid at room temperature, potassium has a melting point of 63°C, and copper metal can be drawn into thin wires.
  • Chemical properties describe the way a substance may change or react to form other substances. Examples of chemical properties: Iron metal rusts in moist atmosphere, nickel dissolves in acid to give a green solution, magnesium bums in presence of oxygen.
  • If a substance possesses a bad property, such as toxicity, it does not mean it cannot be used for the betterment of human society.
  • Carbon monoxide is a gaseous air pollutant present in automobile exhaust and cigarette smoke, and is toxic to human beings.
  • Despite its toxicity, carbon monoxide plays a key role in the maintenance of a high standard of living.
  • Its contribution lies in the isolation of iron from iron ores and in production of steel. MATTER AND ITS PROPERTIES
  • Thus, carbon monoxide is both good and bad substance. A similar ‘good-bad’ dichotomy exists for most chemical substances.

Changes that can occur in matter are classified into two categories: physical and chemical.

  • A physical change is a process in which a substance changes its physical appearance but not its chemical composition.
  • No new substance is formed as a result of the physical change. MATTER AND ITS PROPERTIES
  • Examples: grating of carrot, boiling of water, designing of wood into a table, forming of gold foil from a bar of gold, glowing of an electric bulb, breaking of a glass tumbler, melting of butter, making a salad from raw vegetables and fruits, formation of clouds, stretching of a rubber band, tearing of paper, breaking of a chalk piece, and rotation of a fan.
  • A chemical change is a process in which a substance undergoes a change in its chemical composition.
  • It gets converted into one or more new substances that have properties and composition distinctly different from those of the original substance. MATTER AND ITS PROPERTIES
  • Examples: burning of a match stick, souring of milk, digestion of food, explosion of a fire cracker, cooking of a vegetable, ripening of fruits, burning of fuels and growth of a plant.

Composition of Matter | MATTER AND ITS PROPERTIES

  • Matter is made of tiny particles (atoms or molecules) which are so small that we cannot see them even with a high power microscope.
  • These particles of matter are constantly moving. When a beam of sunlight enters a room, tiny dust particles can be seen moving rapidly in a very haphazard way. This happens because these dust particles are constantly hit by the particles of air which are moving very fast.
  • The zigzag movement of the small particles suspended in a liquid or gas is called Brownian motion. An increase in temperature increases Brownian motion.
  • The spreading out and mixing of one substance with another due to the motion of its particles is called diffusion.
  • Diffusion continues until a uniform mixture is formed. Diffusion is fastest in gases and slowest in solids. As the temperature of the diffusing substance is increased, the rate of diffusion also increases. MATTER AND ITS PROPERTIES

Some of the real life situations involving diffusion are‑

  • We can smell the food cooking in neighbour’s kitchen, the fragrance of burning incense stick or the smell of perfume because of diffusion.
  • The leakage of cooking gas can be easily detected due to diffusion of ethyl mercaptan (a strong smelling substance present in cooking gas) into the air.
  • The spreading of ink or any colour in water is also an example of diffusion.  MATTER AND ITS PROPERTIES
  • Carbon dioxide and oxygen present in air diffuse into water in rivers and seas. This carbon dioxide is used by aquatic plants to prepare food by photosynthesis and the oxygen is used by aquatic animals for breathing.
  • Spreading of virus on sneezing is also because of diffusion.
  • Osmosis can be considered to be a special kind of diffusion. In both diffusion as well as osmosis, particles move from a region of higher concentration to a region of lower concentration.
  • However, diffusion can occur without a membrane or through a perme­able membrane whereas osmosis occurs through a semi-permeable membrane (which allows only solvent molecules to pass through it).
  • Preserving of pickles in salt, swelling up of raisins on keeping in water, and earthworm dying on coming in contact with salt -all display the phenomenon of osmosis.
  • In dialysis, a process similar to osmosis, a semipermeable membrane allows the passage of solvent, dissolved ions and small molecules but blocks the passage of colloidal sized particles and large molecules.
  • The kidneys, a complex dialyzing system, remove waste products from the blood, which are then eliminated in urine.
  • If the kidneys fail, these waste products do not get removed and poison the body. MATTER AND ITS PROPERTIES

Change of State Of Matter | MATTER AND ITS PROPERTIES

The physical state of matter can be changed by changing the temperature or pressure. The process of changing

  • a solid to a liquid by heating is called melting (or fusion)
  • a liquid to a gas by heating is called boiling (or vapourisation)
  • a gas to a liquid by cooling is called condensation
  • a liquid to a solid by cooling is called freezing

Concepts associated with Change of State | MATTER AND ITS PROPERTIES

Latent Heat 

  • The heat energy required to change the state of a substance is called its latent heat.
  • Latent heat does not increase the temperature of the substance but has to be supplied to bring about a change in state.
  • The latent heat which is supplied is used up in overcoming the forces of attraction between particles of the substance undergoing the change of state.
  • Thus, there is no rise in temperature during the melting of ice or boiling of water.
  • The heat required to convert a solid into its liquid state is called latent heat of fusion and the heat required to convert a liquid into its vapour state (or gas) is called latent heat of vapourisation.
  • Ice at 0°C is more effective in cooling a substance than water at 0°C because ice takes its latent heat from the substance for melting and hence cools it more effectively.
  • On the other hand, water at 0°C does not take any such latent heat from the substance.
  • An ice cube held in the hand feels very cold because it takes away latent heat from the hand for melting.
  • When ice at 0°C melts, it requires latent heat of fusion to form water at 0°C.
  • Likewise, when water at 0°C freezes to from ice at 0°C, it liberates an equal amount of heat.
  • When water changes into steam, it absorbs latent heat, and when steam condenses to form water, it gives out an equal amount of latent heat.
  • Burns caused by steam are much more severe than those caused by boiling water, simply because steam contains more heat (in the form of latent heat) than boiling water.
  • Due to the same reason, steam is better than boiling water for heating purposes. MATTER AND ITS PROPERTIES

Sublimation | MATTER AND ITS PROPERTIES

  • The conversion of a solid directly into vapour on heating, and of vapour into solid on cooling, is known as sublimation.
  • Ammonium chloride, iodine, camphor, naphthalene, and anthracene undergo sublimation.
  • Naphthalene balls, used to protect woollen and silk clothes from insects, disappear with time due to sublimation.
  • Gases can be liquefied by applying pressure and lowering temperature. Similarly, decreasing the pressure and raising the temperature can also change the state of matter.
  • Solid carbon dioxide, also called dry ice, is stored under high pressure. MATTER AND ITS PROPERTIES
  • On decreasing the pressure and increasing the temperature, it gets converted directly into carbon dioxide gas, i.e., it sublimes. Dry ice is an extremely cold, white solid, used to ‘deep freeze’ food and keep ice-cream cold. Dry ice is much more effective for cooling than ordinary ice.

Evaporation | MATTER AND ITS PROPERTIES

  • The process by which a liquid changes into vapour even below its boiling point is called evaporation.
  • Evaporation can occur even at room temperature. Drying of wet clothes and recovery of salt from sea water occurs because of evaporation. Evaporation is facilitated by high temperature, large surface area of the liquid, low humidity of air, and high speed of wind.
  • Evaporation causes cooling because when a liq­uid evaporates, it draws the latent heat of evaporation from the surface it touches.
  • Evaporation of ether or spirit from the back of our hand leaves it feeling cool. Evaporation of sweat from our body keeps us cool. Water kept in earthen pots during hot summer days becomes cool because of evaporation of water through the pores in the pot. MATTER AND ITS PROPERTIES

Pure Substances and Mixtures | MATTER AND ITS PROPERTIES

  • Matter can be classified on the basis of its chemical composition as a pure substance or a mixture.
  • A pure substance is made up of only one kind of particles (atoms or molecules). For example, pure water is water and nothing else.
  • Pure copper contains only copper and nothing else. A pure substance always has a definite and constant composition and its properties are always the same under a given set of conditions.
  • A mixture contains two or more kinds of particles, i.e., two or more pure substances mixed together, each of which retains, its own identity.
  • In some mixtures like soil, rocks, and wood, the components are readily distinguished. Such mixtures are heterogeneous. Salt solution, sugar solution, air, petrol and alloys like brass are uniform throughout and are known as homogeneous mixtures.
  • Chocolate-chip cookies and fresh-fruit pudding are heterogeneous mixtures whereas soft drinks are homogeneous mixtures. Some more examples of mixtures: Milk, tea, coffee, gunpowder, sea water, ink, paint, dyes, kerosene oil, glass, coal, blood, soap solution, butter, cheese, face cream, etc.

Pure substances can be further classified as elements and compounds.  MATTER AND ITS PROPERTIES

Elements | MATTER AND ITS PROPERTIES

  • An element is a substance which cannot be broken down into simpler substances by chemical or physical means. It is made up of only one kind of atoms.
  • There are 117 elements known at present, out of which 88 occur naturally and 29 have been synthesized.
  • Elements can be solids, liquids or gases. For example, sodium, magnesium, iron, gold, carbon, and sulphur are solids, mercury is a liquid, and helium, argon, and neon are gases. Astatine is the rarest naturally occurring element in the earth’s crust. 
Some Important Elements and Their Symbols
Element Symbol Element Symbol
Aluminium Al Lithium Li
Antimony Sb Magnesium Mg
Argon Ar Manganese Mn
Barium Ba Mercury Hg
Beryllium Be Neon Ne
Boron B Nickel Ni
Bromine Br Nitrogen  
Calcium Ca Oxygen 0
Carbon C Platinum Pt
Chlorine CI Phosphorus P
Chromium Cr Potassium K
Cobalt Co Radium Ra
Copper Cu Silicon Si
Fluorine F Silver  Ag
Germanium Ge Sodium Na
Gold Au Sulphur S
Helium He Thorium Th
Hydrogen H Tin Sn
Iodine I Tungsten W
Iron Fe Uranium U
Lead Pb Zinc Zn

In the universe, the composition of elements is: Hydrogen: 91 % Helium: 9% and all others < 0.1 %. In earth’s crust, the composition is: Oxygen: 60.1% Silicon: 20.1 % Aluminium: 6.1% Hydrogen: 2.9% Calcium: 2.6%, Magnesium: 2.4%, Iron 2.2%, Sodium 2.1% and all others 1.5%. In human Body, the composition is: Hydrogen: 60.5%, Oxygen: 25.7%, Carbon: 10.7%, Nitrogen: 2.4% and all others: 0.7%. MATTER AND ITS PROPERTIES

The super-heavy element 117 was discovered by a team of Russian and American scientists (April, 2010). It is made of atoms containing 117 protons, and is almost 40% heavier than lead. Six atoms of the element were produced by smashing together isotopes of calcium and a radioactive element, called Berkelium, in a particle accelerator near Moscow. MATTER AND ITS PROPERTIES

 

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