(General Science) CHEMISTRY - Matter and its Properties, Composition, Change of State, Element's Symbol

GENERAL SCIENCE: CHEMISTRY


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 State 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 eg, 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 eg, water, milk, oil and alcohol are liquids.

  • Solid: It has both fixed volume and fixed shape. Neither liquid 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. The forces of attraction between particles are strongest in solids and weakest in gases.

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 temperature.

Properties of Matter


Every substance has a unique set of properties or characteristics that allow us to recognize 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. Example of physical properties: Mercury is a liquid at room temperature, potassium has a melting point of 63 ᵒC, and copper metal can be drawn into thin wires.

Chemical properties describe the ways a substance may change or react to from other substance. Example of chemical properties: Iron metal rusts in moist atmosphere, nickel dissolves in acid to give a green solution, magnesium bums in presence of oxygen.

Composition of Matter


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.

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.
  • Carbon dioxide and oxygen present in air diffuse into water in river 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.

Change of State of Matter


The physical state of matter can be changed by changing the temperature or pressure. The process of changing:
(i) a solid to a liquid by heating is called melting (or fusion)
(ii) a liquid to a gas by heating is called boiling (or vapourisation)
(iii) a gas to a liquid by cooling is called condensation
(iv) a liquid to a solid by cooling is called Freezing

Concept associated with Change of State


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 force 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 oC is more effective in cooling a substance than water at 0 oC because ice takes its latent heat from the substance for melting and hence cools it more effectively. On the other hand, water at 0 oC 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 oC melts , it requires latent heat of fusion to from water at 0 oC. Likewise, when water at 0 oC freeze to from ice at 0 oC, liberates an equal amount of heat. When water changes into steam, it absorbs latent heat, and when steam condenses to from 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.

Pure substances can be further classified as elements and compounds.

Element: An elements 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, liquid or gases. For example, sodium, magnesium, iron, gold, carbon, and sulphur are solid, mercury is a liquid, and helium, argon, and neon are gases. Astatine is the rarest naturally occurring elements in the earth’s crust.

Some Important Elements and Their Symbol


Element

Symbol

Element

Symbol

Aluminium

AI

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

N

Calcium

Ca

Oxygen

O

Carbon

C

Platinum

Pt

Chorine

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

lodine

I

Tungsten

W

Iron

Fe

Uranium

U

Lead

Pb

Zinc

Zn

In the universe, the composition of element is : Hydrogen: 91% Helium: 9% and all other <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 other 1.5%. In human Body, the composition is: Hydrogen: 60.5% Oxygen: 25.7%, Carbon: 10.7%, Nitrogen: 2.4% and all other: 0.7%

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 elements were produced by smashing together isotopes of calcium and a radioactive element, called Berkelium, in a particle accelerator near Moscow.