Current Affairs 4th Class

       States of Matter   Matter is divided into three groups according to the state in which they exist.              Solid In solids, the molecules are very close to one another and the force of attraction among the molecules is great. Arrangement of molecules in solid Because of this close packing and great attraction among the molecules, solids are hard and has a definite volume and definite shape. For example, ice, book, table, etc.                                                         Books                                           Furniture                               Animals                              Plant                Liquids In liquids, the molecules are not packed very close. They can move about more freely because of less attraction among them. Arrangement of molecules m liquid This is the reason for the liquid to flow. So liquid has no definite shape but a definite volume. It takes the shape of the container in which it is put. For example water, milk, cold drink, petrol etc.                                                                                 Water                                            Milk                               Petroleum                                  Cold drink              Gas In gases, the molecules are far apart from one another. They have lots of freedom to move. Hence gas has neither fixed shape nor fixed volume.   Arrangement of molecules in gas         Water vapour, smoke etc.                 Look at the following figure carefully and choose the correct option for it. (a) Gas  (b) Liquid (c) Solid (d) Both A and C (e) All the more...

     Molecules   A smallest particle of matter, which can exist in a free state is called a molecule. Structure of molecules of some elements has been given below.                        Molecules of any given substance are all similar. A molecule is defined as a group of at least two atoms in a definite arrangement. Molecules are formed by the combination of two or more atoms. The Properties of a substance are the properties of its molecule. Molecules can be subdivided to individual atoms. The atoms are bounded together in a molecule. Molecules also are not visible to the naked eye. It can be seen through highly magnifying microscopes and other scientific devices.     Water is comprised of numerous water molecules. Each water molecule is made up of one oxygen atom and two hydrogen atoms. So a water molecule can be further divided into oxygen and hydrogen atoms.         Hydrogen           Oxygen                 Water Schematic Representation of Water Molecule   Group of atoms in a definite arrangement to form molecule                 Consider the statements given below and select the right answer. Statement A: A molecule is defined as a group of at least two atoms. Statement B: Molecules are visible to the naked eye. (a) Statement: A is true (b) Statement: B is true (c) Both Statement: A and B partly true (d) Both Statement: A and B are partly false (e) None of these   Answer: (a)          Molecules of water is made of which one of the following kind of atoms? (a) Helium and Oxygen (b) Nitrogen only (c) Carbon and Hydrogen (d) Oxygen and Hydrogen (e) None of these   Answer: (d)

     Introduction   All the things that we can see around us, whether living or non-living, are matter if it takes up space and has weight. It can be dog, cat, bat, ball, air, water, etc.                                                                                    Matters  Matter is made up of tiny particles. These tiny particles are too small to be seen. Millions and millions of these tiny particles put together to form a matter. These tiny particles are known as molecules. A molecule is the smaller unit of any substance that has all the properties of that particular substance. A molecule of aluminum has all the properties of aluminium. The molecule of different substances are different from each other. For example molecule of aluminium is different from the molecule of iron. The amount of space that a matter takes up is called its volume. .             Atoms Atoms are made up of fundamental particles electrons, protons, and neutrons. Protons and neutrons lie in the center of the atom and electrons are moving around the nucleus in certain orbit.             Diagrammatic representation of Atom All materials of the universe are made up of minute particles called atoms. Structure of atoms of some elements has been given below                                                  Atom of hydrogen                      Atom of carbon                           Atom of nitrogen                            Atom of lithium                    Atom of oxygen   Atoms are the basic building blocks of matter. Atoms can join together to form molecules, which in turn form the objects around us. It is not possible to breakdown the atom further retaining the properties of the element. Atoms are not visible to the naked eye. For example the atoms of the element carbon cannot be further broken down and each part has the properties of carbon.                      Consider the statements given bellow and select the right answer. Statement A: Molecules are made up of atoms. Statement B: At the center of an atom is the nucleus. (a) Statement: A is True (b) Statement: B is more...

     Nervous system   Nervous system co-ordinates all our body functions. It consists of brain, spinal cord and the nerves. Brain is our body's control system. Brain sends messages and receives them from all organs, all over the body. Brain is divided into 3 parts         Human Brain Accounts for 85% of our brain's weight. It consists of two -halves, right half and left half. The right half, which helps to think about things like colour, different shapes, etc. The left half is responsible for speech, maths, and logic. It is also known as the forebrain.            Cerebellum It is also called the Hindbrain, and is much smaller than forebrain. It is responsible for the movement of our body and maintaining body balance.            Medulla Oblongata It joints brain and the spinal cord. Functions like digestion, blood pressure, breathing, etc. is controlled by this organ.                  Nerve Spinal cord is a mass of nerves running down the middle of the backbone. A fine network of nerves connects the brain and the spinal cord to every part of our body. They carry messages to and from the brain to the body part. Nerves present in our body are of two main types. The sensory nerves, which carries messages from the sense organ to the spinal cord or the brain. Motor nerves which carries messages from the brain or the spinal cord to various parts of the body. 90% of full weight of the brain is achieved at the age of 5 years.               Human nervous system consists of (a) Brain (b) Spinal cord (c) Nerves (d) All of these                                  (e) None of the above   Answer: (d)           Nerves which carry the messages from the sense organs to the spinal cord or brain are (a) Motor nerves                                             (b) Sensory nerves (c) Both type of nerves carry messages to the brain (d) All of the above                                         (e) None of the above   Answer: (b)     The stomach's digestive acids are strong enough to dissolve zinc. Fortunately for us, the cells in the stomach lining renew so quickly that the acids don't have time to dissolve it. Each finger and toenail takes six months to grow from base to tip. The lungs contain over 300,000 million capillaries (tiny blood vessels). If they were laid end to end, they would stretch 2400 km.     Nutrients: The component of food which is necessary for our body. Sense Organ: more...

     Excretory system   Excretory system throws out waste from our body. Human excretory system consists of kidneys, ureter urinary bladder and urethra.                 Excretory System We have a pair of kidneys which is bean shaped. When the blood reaches the kidney it has both useful and harmful substance present in it. The kidneys absorb harmful substance from the blood. The waste is dissolved in water and is removed as urine. The urine from the kidney goes to the urinary bladder through tube like urethras. Urethra has an opening at end of the muscular tube through which urine passes out. The skin also helps in removing waste from our body in the form of sweat. Lungs act as excretory organ by removing carbon dioxide (harmful gas) from the body.                A person has been put on dialysis. Which one of his following organs has failed to work? (a)                         (b)        (c)       (d)      (e) All of these     Answer: (C)            Which one of the following is a part of excretory system? (a) Stomach (b) Liver (c) Heart (d) Kidney (e) All of these   Answer: (d)

     Circulatory System   Circulatory system circulates blood throughout the body. It takes oxygen and food to every body cells and sweeps out carbon dioxide and other waste materials. It also helps in fighting infection and keeps our body warm. The circulatory system consists of the heart, blood vessels and the blood. Our heart is a powerful pump made of muscle. It contracts and relaxes automatically about 72 times a minute to pump blood around the body. Our heart is placed in the middle of our chest, slightly to the left.    Circulatory System              Our heart Our heart has two sides, the right and the left one. The right side pumps blood only to the lungs. The left side, which is the bigger of the two sides pumps blood throughout the body. Blood vessels are thin tube through which blood travels throughout the body.                                                  Our Heart                  Which one of the following is a part of circulatory system? (a) Heart  (b) Blood (c) Blood vessels (d) All of these                                  (e) None of these   Answer: (d)            Which one of the following can be termed as "pumping machine?" (a) Lung (b) Nerves (c) Kidney (d) Heart                                              (e) None of these   Answer: (d)

     Respiration in Human   Respiration is a process by which body burns organic matter (glucose) in the presence of oxygen to release energy. This energy is needed for work, growth, development and maintenance of the body. The human respiratory system consists of nose, windpipe and lungs. We breathe air through our nose. The air has oxygen in it. This air now moves down from windpipe to the lungs. The lungs are present inside our rib cage. We have a pair of them. It is a soft spongy bag like organ. Each of our lungs has millions of branching air sacs known as bronchioles.   Respiration in Human At the end of each bronchioles there are bunches of air sacs known as alveoli. During the process of respiration, oxygen from the air seeps through the air sacs into the blood and at the same time carbon dioxide seeps back into the air sac and is thrown out when we breathe out.                   When a person runs or does some hard physical work, what happens to his breathing? (a) Breathes faster (b) Breathes slow (c) Breathes at the normal rate (d) None of these (e) All of these   Answer: (a)          Name the gas that all living things breathe in (a) Oxygen (b) Carbon dioxide (c) Hydrogen (d) Nitrogen (e) All of these   Answer: (a)

     Digestion of Food   Digestion is the process of breaking down food into simple form so that it is easily absorbed by the body. Digestion of food takes place in a number of steps. There are several organs of our body, which are involved in this process. They all together make up our digestive system. Digestion of food starts in the mouth. The food is broken down by chewing and grinding into a paste. The paste next moves to the stomach through the food pipe. Food is churned by the stomach muscles with more digestive juices. It is then broken down into simple soluble form. The simpler food now passes to the intestine. Here the food is mixed with more digestive juices and breaks down further. Some of these digestive juices come from the intestine, while other is made in other body organs such as liver and pancreas. These juices complete the digestion of food. The food is now in simple soluble form, which can easily be absorbed into the blood through the walls of the small intestine. The undigested food pass through the large intestine and thrown out of the body through the anus.                    Where does the digestion of food start in our body? (a) Stomach  (b) Small intestine (c) Large intestine    (d) Mouth (e) None of these   Answer: (D)              Which of the following is not a part of the digestive system? (a) Mouth (b) Food pipe (c) Windpipe   (d) Stomach (e) Intestine   Answer: (C)

     Nutrients   All living thing needs food for its growth, maintenance and development. Food has different components. These components are called nutrients. Each nutrient is required in specific amount and has a specific function. Food is divided into different groups according to the function they perform in the body.              Carbohydrates Carbohydrates provide energy to our body. We need energy to do any kind of work. Example bread, chocolates, sweet Potatoes and Banana.                  Carbohydrate Rich Food                Proteins They are the body building nutrients. We need protein for our growth. They build muscles and repair the damaged parts of our body. Children need more protein than adult because their body parts need to grow and get bigger. Milk, egg, fish, meat, cheese curd, pulses and beans etc. are protein rich food.               Protein Rich Food                Fat Fat gives energy and warmth. They give us more energy and heat than carbohydrates. Fat are stored in the body for future use. This stored energy is used when the body does not get enough food to eat. Example: Cheese, butter, oil, nuts are all rich in fat.             Fat Rich Food              Vitamins and minerals Vitamins and minerals are the protective nutrients. These food nutrients protect us from diseases and keep us healthy and fit. These are needed in very small amounts. Example fresh fruits, vegetables, eggs, milk are rich source of vitamins and minerals. Food items rich in vitamins and Minerals              Roughage and water Apart from nutrients, our body also needs dietary fibers, which help us to keep our bowl clean by adding bulk to it. These dietary fibers also know as roughage. Roughage is mainly provided by plant products in our food. Fresh fruits and vegetables, whole grain pulses are main source of roughage. It does not provide any nutrient value to the body but still is very important. It help us to get rid of undigested food with ease. Water helps in absorption of nutrients from the food. It also plays a major role in throwing out wastes like sweat, urine from the body. Most of the water requirement is fulfilled by the liquids we drink. Fruits and vegetables also provide water.                 Roughage and Water                   Which one of the following food is more...

     Functioning of Human Body   Human body is a complex, well-coordinated, wonderful and a beautiful looking machine. We have different systems working independently and doing its work without any fuss or irregularities.          We can say that our body follow the rule of division of labour. We have different systems like the digestive system whose function is digesting of food, circulatory system which supplies food and oxygen to the required cells and collects waste from all body parts. Nervous systems which coordinates all our body function. Respiratory system is concerned with the release of energy from the food. Excretory systems excretes the waste material from our body. Reproductive system is involved in reproduction, i.e., producing young ones. The functions of these systems are monitored by the brain. These systems are made up of many organs working together for a common function. For example, digestive system consists of mouth salivary glands, oseophagus, stomach, liver, gall bladder, pancreas, small intestine large intestine, rectum and anus. Other than organs of the systems we have the sense organs which helps us to see, feel, hear, smell and taste. The human body is also wonderfully packed with each organ placed at proper point with all care and protection. The soft organs of the body are protected by the hard outer covering of the rib cage and the bones. The organs of our body function all the time..