4th Class

Plants   We often see beautiful trees, plants full of green leaves, around us. But do we ever think why the leaves of trees are green? Have you ever seen plants having coloured leaves? The leaves of most of the plants are green because their leaves contain a green coloured pigment called chlorophyll. Green leaves are responsible for making food. Thus, they are also known as food factories of the plants. Plants uses carbon dioxide, sunlight and water for making food. Upper surface of a leaf has more chlorophyll for trapping the sunlight. On the undersurface of the leaf, there are tiny pores known as stomata which can only be seen through microscope. The stomata are responsible for exchange of gases in plants. Water and essential minerals are absorbed by the roots of the plant from soil and then It is transported to leaves more...

Animals   Animals are living beings that can move and produce young ones. The process of producing young ones is called reproduction. Different animals reproduce by different methods. Some animals lay eggs and some give birth to young ones.   Egg Laying Animals Several types of animals like birds, reptiles, insects and amphibians lay eggs. An egg is an organic vessel in which an embryo begins to develop.   Birds Birds lay eggs which have a hard, protective shell. It contains a yellow yolk surrounded by white albumen. The yolk provides food to the chick growing inside it. The growing chick is called embryo. The parent bird sits on the egg to keep it warm. The chick breaks the shell and comes out when it has grown. This is called hatching.   Insects Insects also more...

Functioning of Human Body   All human beings require energy for doing various kinds of activities. They get this energy from food that they eat. The food we eat cannot be used by our body directly. It has to be broken down into a simpler form. Our body has a system for breaking down the food into a simpler form. This system is called digestive system.   Digestive System The process of digestion takes place in the following steps:  

• First, we eat food which goes into the mouth. Our mouth has teeth for chewing and cutting the food into smaller pieces. Thus, the process of digestion begins in the mouth. In the mouth, a digestive liquid called saliva mixes with food to make it a fine paste. Saliva breaks down food into starch and soluble sugar.
• Food then more...

Measurement   We need to measure many different things in our daily life like length of objects, height, weight (of fruits, vegetables, etc.) amount of milk, water and so on.       Measurement of Length In early days, people used body parts to measure lengths.                      Cubit                                                   Hand span    The metre is what we normally use for measuring lengths. Smaller lengths are measured centimetres. Metre is written as m and centimetre as cm.   Measurement of Mass Mass tells us how heavy or light more...

Matter and Materials   Matter Anything that occupies space and has mass is called matter. Everything around us is made up of matter. Matter is made up of atoms. Water bottle, school bag, rubber, pencil are all made up of matter.   States of Matter Matter exists in three forms - solid, liquid and gas. Matter can change from one form in other on heating and cooling.   Changes Around Us Matter is constantly changing around us. Changes are of two types — physical changes and chemical changes. In physical change, no new substance is formed. Breaking of glass, melting of ice into water are some examples of physical change. When ice melts the solid water turned to liquid water. It doesn't turn into food or cold drink or anything new. more...

Force, Work and Energy   Whenever we push or pull an object, we apply force. A force can make an object move, can stop a moving object, can change direction of a moving object and can change the shape of an object.   Types of Force There are different types of forces: Muscular Force the force exerted by muscles of our body. For example, lifting a bucket, lifting dumbbells, etc. A Man lifting a dumbbells     Elastic Force It is the force exerted when an elastic material is stretched. For example, stretching of rubber band. Stretching a rubber band   Frictional Force                                                 It is the force exerted by two more...

Our Environment   Our Environment is composed of physical and biological things surrounding us. It has physical or abiotic factor and biological or biotic factor. Physical components includes air, water, minerals and other non-living things around us. Biological components includes plants, animals and micro- organisms.   Pollution Pollution is the undesirable change in the physical, chemical and biological constituents our surroundings. Pollution is of various types:   Air Pollution Air pollution occurs when the air contains dust particles, gases, fumes in that amount which is harmful for us. The substances causing air pollution are called air pollutants. Industries and vehicles discharge harmful gases into the air making it dirty and unfit for breathing.   more...

Our Universe   Our Universe Our universe consists of number of stars, planets including our earth and moons.   Solar System     The sun and the eight planets belong to a family called solar system. The eight planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. All of them revolve in fixed path called orbit. Planets rotate on their axis also. Most planets have their satellites which revolve around them. Satellite does not have its own light. Man has also made ne satellites for weather forecasting and to help in communication which are known as artificial satellites, for example, Aryabhata, Rohini etc.   Stars and Planets A star is a huge ball of hot gases. It gives out heat and light. Planets do not have any or light of more...

Reasoning and Aptitude   Introduction Learning process is dependent on ones ability to think logically and reason quickly and effectively. So Reasoning and logic skills are an important part in our progress 55 these skills are very useful in our day to day life. In this chapter, we will learn various problems related to reasoning and aptitude.   Problems Based on Patterns Pattern is a list of numbers or letters that follows a certain sequence or a certain rule. To find the missing term or next term in series to continue the given series, first we must have a rule. To solve them all, we have to do is figure out the pattern and come up with the next logical number or letter of the sequence.  

• Example:

The values of A and B in the given number pattern are: more...

Comprehensions   Reading comprehension is an essential part of any test of English language. In this, a passages is given. You have to read the passage carefully and answer the questions based it.  

•                    Example 1                            

Read the passage carefully and answer the   questions that follow: If you decide to become a paleontologist you would study plants and other organisms that lived in pre-historic times. That would be a time more than 5,500 years ago. more...