Articles

There are many professionals who provide their services against payment of their fee. Thus, all types of services are special skills provided in exchange of payments. Health, education, law, governance and recreation etc. require professional skills.

All economic activities namely primary, secondary, tertiary and quaternary, revolve around obtaining and utilising resources necessary for survival.

Human activities which generate income are known as economic activities. Economic activities are broadly grouped into primary, secondary, tertiary and quaternary activities.

The people of a country are its real wealth. It is they, who are the actual resources and make use of the country’s other resources and decide its policies. Ultimately a country is known by its people.

The Last Lesson is set in the days of the Franco-Prussian War (1870-1871) in which France was defeated by Prussia led by Bismarck. Prussia then consisted of what now are the nations of Germany, Poland and parts of Austria. In this story the French districts of Alsace and Lorraine have passed into Prussian hands.

The amount of carbon present in the earth’s crust and in the atmosphere is quite meagre. The earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, hydrogen-carbonates, coal and petroleum) and the atmosphere has 0.03% of carbon dioxide. In spite of this small amount of carbon available in nature, the importance of carbon seems to be immense.

Elements can be classified as metals or non-metals on the basis of their properties.

All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature.

An electric current-carrying wire behaves like a magnet. Electricity and magnetism are linked to each other.

Electricity has an important place in modern society. It is a controllable and convenient form of energy for a variety of uses in homes, schools, hospitals, industries and so on.

The human eye uses light and enables us to see objects around us. It has a lens in its structure.

An object reflects light that falls on it. This reflected light, when received by the eyes, enables to see things.

Reproductive processes give rise to new individuals that are similar, but subtly different. Some amount of variation is produced even during asexual reproduction. The number of successful variations are maximised by the process of sexual reproduction.

Organisms look similar because their body designs are similar. If body designs are to be similar, the blueprints for these designs should be similar. Thus, reproduction at its most basic level will involve making copies of the blueprints of body design.

In animals, control and coordination are provided by nervous and muscular tissues.

The biological process involved in the removal of these harmful metabolic wastes from the body is called excretion. Different organisms use varied strategies to do this.

Blood transports food, oxygen and waste materials in our bodies. Blood consists of a fluid medium called plasma in which the cells are suspended. Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form.

The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways - some use oxygen to break-down glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen.

When we walk or ride a bicycle, we are using up energy. Even when we are not doing any apparent activity, energy is needed to maintain a state of order in our body.

The maintenance functions of living organisms must go on even when they are not doing anything particular. Even when we are just sitting or even if we are just asleep, this maintenance job has to go on. The processes which together perform this maintenance job are life processes.

On the morning of 14 July 1789, the city of Paris was in a state of alarm. The king had commanded troops to move into the city. Rumours spread that he would soon order the army to open fire upon the citizens.

Acids are sour in taste and change the colour of blue litmus to red, whereas, bases are bitter and change the colour of the red litmus to blue.

Whenever a chemical change occurs, a chemical reaction has taken place.

Sound is a form of energy which produces a sensation of hearing in our ears.

Two conditions need to be satisfied for work to be done: (i) a force should act on an object (ii) the object must be displaced. If any one of the above conditions does not exist, work is not done.

A force is needed to change the speed or the direction of motion of an object. An object dropped from a height falls towards the earth. All the planets go around the Sun. The moon goes around the earth.

A force can be used to change the magnitude of velocity of an object (to make the object move faster or slower) or to change its direction of motion. A force can change the shape and size of objects.

To describe the position of an object you need to specify a reference point called the origin. Motion is a change of position. It can be described in terms of the distance moved or the displacement.

All living organisms are made of cells. In unicellular organisms, a single cell performs all basic functions. For example, in Amoeba, a single cell carries out movement, intake of food, gaseous exchange and excretion.

The fundamental organisational unit of life is the cell.

Atoms and molecules are the fundamental building blocks of matter. The existence of different kinds of matter is due to different atoms constituting them.

Ancient Greek philosophers, Democritus and Leucippus suggested that if we go on dividing matter, a stage will come when particles obtained cannot be divided further. Democritus called these indivisible particles atoms.

All living organisms need food. Food supplies proteins, carbohydrates, fats, vitamins and minerals. Both plants and animals are major sources of food. We obtain most of this food from agriculture and animal husbandry.

Mixtures are constituted by more than one kind of pure form of matter. Dissolved sodium chloride can be separated from water by the physical process of evaporation. However, sodium chloride is itself a pure substance and cannot be separated by physical process into its chemical constituents.

Matter is made up of small particles. The matter exists in three states - solid, liquid and gas. The forces of attraction between the particles are maximum in solids, intermediate in liquids and minimum in gases.

While there are billions of planets in the universe, Earth is the only one where life, as we know today, exists and thrives in all its forms.

The living beings are termed as the biotic components and non-living things as the abiotic components of a habitat.

The bright portion of the Moon decreases from a full circle to a half circle in about a week.

Spherical mirrors are a common type of curved mirrors which are shaped like a part of a hollow glass sphere. Mirrors, whose reflecting surfaces are spherical are called spherical mirrors.

When salt and sugar are mixed with water, a uniform mixture is formed, whereas when chalk powder or sand, or sawdust is mixed with water, the components are not evenly distributed. Such mixtures are known as non-uniform mixtures.

When two or more substances are mixed, where each substance retains its properties, it is called a mixture. The individual substances that make up a mixture are called its components.

A constituent particle is the basic unit that makes up a larger piece of a substance or material. The spaces between the particles are known as interparticle spaces.

When we carry a bag, we feel its weight because of the force of gravity acting on our shoulders. The weight of the bag with narrow straps acts on a smaller area of our shoulders, whereas the weight of the bag with broad straps is spread out over a larger area of our shoulders.

In everyday life, we come across many situations where a force is applied, for example, opening a drawer, stretching a rubber band, a fielder stopping a ball, kicking a football, applying brakes on a moving bicycle, rolling a chapati, or turning the steering handle of an auto rickshaw.

When the current flows, the compass needle gets deflected from its original direction. When the current stops, the needle returns to its original direction.

There was a boy called Mario who loved to have lots of friends. He showed off a lot, always talking about how many friends he had at school, and how he was so friendly with everyone.

May my friendships always be
The most important thing to me.

Gajaraj, the elephant, lived in the best booth of the royal stables. The king was fond of Gajaraj, and he had ordered that the elephant should be well looked after.

Mr Raven was perched upon a limb,
And Reynard the Fox looked up at him;
For the Raven held in his great big beak,
A morsel the Fox would go far to seek.

Rama Natha was the son of a rich landlord. His father left him large tracts of land when he died. But Rama Natha did not spend even one day looking after his land.