Atoms and Molecules
Matter is made up of small particles called molecules. Atoms combine to form molecule. Different atoms and molecules have different properties due to which different matters show different properties.
Laws of Chemical Combination
The laws of chemical combination are:
Law of conservation of mass
Law of constant proportions
Law of Conservation of Mass
This law states that in a chemical reaction, the total mass of products is equal to the total mass of reactants. There occurs no change in mass during a chemical reaction. For example, in the following chemical reaction:
Sodium carbonate + ethanoic acid \[\to \] sodium ethanoate + carbon dioxide + water
The addition of mass of sodium carbonate and ethanoic acid will be equal to the addition of mass of sodium ethanoate, carbon dioxide and water.
Law of Constant Proportions
Law of constant proportions states that chemical compound always consists of the same elements combined together in the same proportion by mass. For example, water is a chemical compound that is always composed of hydrogen and oxygen combined in the some constant proportion of 1:8 by mass.
Dalton's Atomic Theory
Dalton's Atomic theory of matter states that all matter is made up of very small indivisible particles. Dalton gave his atomic theory of matter in 1805. The various postulates of Dalton's atomic theory of matter are:
(i) All the matter is made up of very small particles called atoms.
(ii) Atoms cannot be divided.
(iii) Atoms can neither be created nor destroyed.
(iv) Atoms are of various types.
(v) All atoms of given element are identical, having same mass, size and chemical properties.
(vi) Atoms of different elements differ in mass, size and chemical properties.
(vii) Chemical combination between two or more elements consists in the joining together of atoms of these elements to form molecules of compounds.
(viii) The number and type of atoms in a given compound is fixed.
(ix) During chemical combination, atoms of different elements combine in small whole numbers to form compounds.
(x) Atoms of the same elements can combine in more than one ratio to form more than one compound.
Limitations of Dalton's Atomic Theory
Some of the statements of Dalton's atomic theory are not correct. The following are the limitation of Dalton's atomic theory:
(i) One of the main limitations of Dalton's atomic theory of matter is that atoms were thought to be indivisible. Now it is known that atoms can be divided into. smaller particles called electrons, protons and neutrons.
(ii) Another limitation is that this theory assumes that all the atoms of an element have exactly the same mass. Now it is known that atoms of the same element can have slightly different masses. These atoms are called isotopes.
(iii) Another limitation is that this theory assumes that atoms of different elements have different masses. Now, it is known that even more...
Cells and Tissues
Cell
Tie cell is the basic structural and functional unit of living organisms.
All living organisms are made up of the smallest unit that is cell. The organisms can be of two types unicellular and multicellular. The unicellular organisms such as amoeba, Paramecium has a single cell in their body and this single cell performs all basic life activities. The multicellular organisms such as human beings have millions of cells in their body. Most of these cells are specialised to carry out a few functions efficiently. A group of cells is responsible for performing a specific function. For example, muscle cells contract and relax to cause movement of a body part.
Structure of a Cell
Different cells have different types of structures which depends on their specific functions. The size, shape, number and volume vary largely in multicellular and unicellular organisms. The size of the cell of bacteria is smallest and ostrich egg is largest. The volume of a cell is constant for a particular cell type and is independent of the size of the organism. For example, kidney or liver cells of a bull, horse and mouse are same in size. The number of cells depends on the types of organisms. It is indefinite in multicellular definite in unicellular.
Plant Cell
Different parts of a cell and their functions:
Plasma membrane - outermost covering of the cell which allows only selective substances to pass through it.
Cytoplasm - helps in exchange of materials between different cell organelles.
Endoplastic reticulum - helps in synthesis and transport of proteins and fats.
Mitochondria - oxidises food to release energy in the-from of ATP.
Golgi apparatus - helps in storage of secretory products.
Ribosomes - helps in protein synthesis.
Lysosome - helps in intra-cellular digestion.
Nucleus - helps in cell division and regulates all functions within the cell.
Nucleolus - helps in protein synthesis by forming and storing RNA.
Vacuoles - helps in storage of water and other substances.
Difference Between Diffusion and Osmosis
Diffusion
Osmosis
1. It is a process of movement of molecules or ions of a substance from a region of higher concentration to a region of their lower concentration.
Diversity in Living Organisms
Diversity in Living Organism
This world is full of living and non-living things. Large variety of living organisms is found on this planet. There is a great diversity among them. From the microorganisms to well-developed animals, one can notice the diversity at all levels.
Basis of Classification
Classification is a method of arranging organisms into groups or sets on the basis of similarities and differences. The study of classification is known as taxonomy. The process of classification began hundreds of years ago. First animals were classified according to whether they lived on land, in water or in the air, but this classification was not adequate. So the need of more accurate form of classification was realised and thus some characteristics were used as a basis for making the broadest divisions for making groups and subgroups.
Classification and Evolution
All living things are categorised on the basis of their body design the and function. The characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later. This clearly indicates that the classification of life forms is directly and very closely related to the evolution. Charles Darvin the renowned biologist first described the idea of evolution in 1859 in his book
"The Origin of Species".
Hierarchy of Classification
H. Whittaker in 1969 proposed five kingdom classification. They are as following:
Force and Motion
Motion
The movement of a body is called motion. The body that is in motion changes its position with time. Therefore, a body is said to be in motion when its position changes continuously with respect to a stationary object taken as a reference point.
Distance
The distance travelled by a body is the actual length of the path covered by a moving body irrespective of the direction in which body travels.
Displacement
When a body moves from one position to another position, the shortest distance between initial and final position of the body along with the direction is known as its displacement.
The actual pength of the path travelled to reach R, starting from P is PQ + QR = 8 + 6=14 km. So, 14 km is the distance travelled by a person.
The shortest distance from P to R is 10 Km, which is the displacement from P to R in north direction.
Scalar Quantity
A physical quantity having only magnitude or size is known as scalar quantity. It does not have direction. For example, distance.
Vector Quantity
A physical quantity having magnitude or size and direction is known as vector quantity. For example, displacement.
Types of Motion
The following are the different types of motion:
Uniform Motion
If a body travels equal distance in equal intervals of time, no matter how small these time intervals are then it is called uniform motion.
Distance-time graph for a body having uniform motion
Non Uniform Motion
If a body travels unequal distance in equal intervals of time then it is called non uniform motion.
Distance-time graph for a body having non uniform motion
Speed, Velocity and Acceleration
Speed
The distance travelled by a body per unit time is called speed.
Speed = Distance / Time taken
The S.I. unit of speed is metre per second (m/s).
Example:
Bus travels a distance of 200 km in 8 hours, then calculate the speed of the bus.
Solution:
Speed = 200 km/8 hours
Speed = 25 km/h
Average Speed
The average speed of a body is the total distance travelled divided by the total time taken to cover this distance.
\[\text{Average}\,\text{speed}\,\text{=}\frac{\text{Total}\,\text{distance}\,\text{travelled}}{\text{Total}\,\text{time}\,\text{taken}}\]
Note:
(i) When the distance travelled in two cases is same, then
\[{{\text{V}}_{\text{av}}}\text{=}\,\frac{\text{2}{{\text{V}}_{\text{1}}}{{\text{V}}_{\text{2}}}}{{{\text{V}}_{\text{1}}}\text{+}{{\text{V}}_{\text{2}}}}\]
(ii) When time taken in two cases is more...
Gravitation
Gravitation
When we throw .an object in upward direction it comes down automatically. This happens because of the force of gravitation. Actually the earth exerts a force of attraction that is called gravity on the object and pulls it down.
Isaac newton
The gravitational force was discovered by Sir Isaac Newton. One day he was sitting under an apple tree, suddenly an apple fell down from the tree. He started thinking about it. He concluded that the earth has certain force that attracted the apple. Finally he concluded that the earth attracts all the objects towards its centre and this force of attraction is called gravitational force of the earth or the gravity. The gravitational force of the earth is responsible for many phenomenons that take place around us. For example, the gravitational force is responsible for holding the atmosphere of the earth, falling of rain on the earth, flowing water in the rivers, walking, etc.
Every object in the universe attracts every other object with a certain force that is called gravitational force. The masses of the objects decide the amount of gravitational force a body can have. When we throw a stone in upward direction, it comes down after attaining a certain height. The earth pulls the stone towards its centre. The stone also pulls the earth toward it with the same force. As mass of earth is very large therefore the accleration produced becomes negligible. Due to this reason we do not see the earth moving towards the stone.
Universal Law of Gravitation
The great scientist Newton has given us the universal law of gravitation. According to this law, every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The direction of the force is along the line joining the centres of two objects.
Gravitational force is directed along the line joining the centre of uniform objects
Let two objects P and Q of masses M and m lie at a distance d from each other, as shown in the above figure. Suppose the force of attraction between two objects is F. As per the universal law of gravitation, the force between the two objects is directly proportional to the product of their masses.
Therefore,\[F\propto M\times m\] —————— (1)
The force between two objects is inversely proportional to the square of the distance between them.
Therefore, \[F\propto \frac{1}{{{d}^{2.}}}\] ————— (2)
From equation (1) and (2) we get
\[F\propto \frac{M\times m}{{{d}^{2}}}.\]
Or, \[F=G\frac{M\times m}{{{d}^{2}}}\]—————(3)
Where G is constant of proportionality, it is called the universal gravitational constant.
The value of G is \[6.673\times {{10}^{-11}}N{{m}^{2}}/k{{g}^{2}}\]
The S.I. unit of G can be obtained by substituting the units more...
Work, Energy and Sound
Work
In Physics work refers to any activity that produce motion. Work is done only when the resultant force and displacement are not zero. The amount of work done by a particular force largely depends on the two factors that are magnitude of the force applied and displacement of the body. We can say that work done in moving a body is equal to the product of force exerted on the body and the displacement moved by the body in the direction of force.
\[Work=Force~\times Displacement\]
OR
\[W=F\times S\]
The S.I. unit of work is joule. If a force of 1 Newton moves a body through a displacement of 1 m in its own direction then the work done is known as 1 joule.
1 joule\[=1\,\,N\times 1\,\,m\]
Work is a scalar quantity.
When a ball is thrown up, its motion is opposed by the earth's gravity. In such case, the work done by the gravitational force of the earth on the ball is given by
\[W=F\times (-S)=-F\times S\]
Thus, the work done by the force is negative.
Example:
A man lifts a luggage of 10 kg from the ground and puts it on his head 1.5 m above the ground. Calculate the work done by him on the luggage.
Solution: Mass of luggage, \[m=10\,\,kg\]
Displacement,\[s=-1.5\,\,m\]
Work done, \[W=F\times S=mg\times S\]
\[=10\,\,kg\times 10\,\,m{{s}^{-2}}\times 1.5\,\,m\]
\[=150kg\,\,m\,\,{{s}^{-2}}m\]
\[=150\,\,N\,\,m=150\,\,J\]
Work done is\[150\,\,J\].
Energy
Energy is the capacity or ability to do work. Without energy life is impossible. The demand of energy has been increasing very rapidly day by day. The sun is the biggest natural source of energy for us. The amount of energy possessed by a body is equal to the amount of work a body can do when its energy is released. Energy has magnitude only. Therefore, it is a scalar quantity. The S.I. unit of energy is joule, which is denoted by the letter J. The energy required to do 1 J of work is called 1 J energy.
Forms of Energy
There are different forms of energy. The two main forms of energy are kinetic energy and potential energy.
Kinetic Energy
Moving ball and a running boy possesses kinetic energy
The energy of a body due to its motion is called kinetic energy. A moving object can do work. For example, moving bullet, rotating of a wheel, moving hammer, blowing wine etc can do the work. In other words, we can say that every object around us which is moving possesses kinetic energy. When a moving object is stopped by an opposite force, the kinetic, energy is lost. The formula of kinetic energy is:
Kinetic Energy \[=\,\frac{1}{2}\,\times \,m\,\times \,{{v}^{2}}\]
Where:
m = mass of an object in Kilograms
v = speed of an object in m/s
The unit of more...
Why do we fall Ill
Health is the real wealth. But health and disease are among the most complicated issues in our life. We have to deal with this issue in our life more often. The most important thing to know is that why we fall ill? It has been rightly said prevention is better than cure. The various organ systems in our body work smoothly to keep us healthy.
Health and Its Failure
Health is an idea of being well. A good health allows us to work well physically, mentally and socially. A good health enables us to cope up with the social, mental and physical pressure without any difficulty. To keep ourselves fit and healthy we must take a balanced diet, regular exercise and cleanliness in and around us. If we do not follow the above mentioned points then we may fall ill. A disease can also be caused because of the malfunctioning of some nutrients or failure of our organs.
Individual and Community Health
As we have mentioned earlier that health means a state of physical, mental and social well-being, but it cannot be achieved at an individual level. The health of all the organisms depends on the environment and their surroundings. We live in a society because our social environment is an important part of our individual health. In the community, physical environment is directly related to social environment. There are various agencies in our communities that are responsible for providing cleanliness. If they will not work properly then we cannot expect healthy life. For example, in a city if garbage is not dumped properly or drains are not cleaned then our community can become a breeding place for disease causing bacteria and germs. In a community, the availability of lean drinking water, adequate nutritious food, social equality and harmony needs to be provided to keep all the people healthy.
Disease and Its Causes
There are various organ systems in our body that work collectively to keep us healthy. A disease can occur when the normal state of a man is disturbed or a particular organ or organ system starts malfunctioning. The cause of disease arise from person to person and from place to place.
The following table provides a list of disease in human and its causes:
Natural Resources
Our earth is a unique planet. It supports all forms of life. To support all these forms of life, the nature has endowed this planet with vast resources such as land, air, water, atmosphere, minerals, etc. All these resources are divided into two components, biotic and abiotic. Biotic components constitute all the living things whereas abiotic components constitute all the non-living things.
Abiotic Components
Abiotic components consist of air, water, soil, land, weather, climate, etc. These all components are very vital to support all forms of life on this planet.
Air
Air is a mixture of many gases such as nitrogen, oxygen, carbon, water vapour, etc. Air is one of the most important factors that supports life on this planet. Our atmosphere constitutes the air. The sunlight is filtered by this atmosphere so that no harmful rays can reach to the earth. The atmosphere has five layers. They are the following:
(i) Troposphere
(ii) Stratosphere
(iii) Mesosphere
(iv) Thermosphere
(v) Exosphere
The atmosphere
The Movement of Air: Wind
Cool breezes that blow on the earth are called winds. They bring a great relief after a hot day. All the phenomena such as the causes of the movement of air, speed of wind, rainfall, etc. are the result of changes that take place in our atmosphere due to the heating of air and the formation of water vapour. Water vapour is formed due to evaporation of water. The atmosphere gets heated from the radiation that is reflected back or reradiated by the land or water bodies. Convection currents are set up in the air when it gets heated.
Air Pollution
Air pollution is like a giant monster which has been destroying the life from the earth slowly and gradually. The process of deforestation has deteriorated the quality of air that directly affects our health.
The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur. Inhalation of these gases is very dangerous for our health. They also cause acid rain as the air in the atmosphere is mixed with these gases. The combustion of fossil fuels also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. Presence of high levels of all these pollutants reduced the visibility. Especially in cold weather when water also condenses out of air. This is known as smog and is a visible indication of air pollution. Air pollution can cause respiratory problems, skin disease, cancer, high blood pressure, irritation, etc. It also affects the life cycle of plants and several other animals. The increase amount of carbon dioxide in the atmosphere is causing green-house effect and damaging the ozone layer, which protect the earth from more...
Improvement in Food Resources
Improvement in Food Resources
Food is our basic need. From food we derive energy to do all activities. In the last few decades, the population of our country has increased manifold. To provide the food security to this growing population is really a onerous task. It is necessary that there should be an improvement in food resources so that we can provide the food security to our people. Our government has made efforts to meet the food demand by increasing food production. The efforts have brought successes up to a certain extent. The green revolution has increased the production of food grains manifold. The white revolution, has led to better and more efficient use as well as availability of milk. The above mentioned revolutions have led to the extensive use of our resources that cause imbalances. We need to follow the method of sustainable development to ensure the conservation of our natural resources. Food security can be provided to the common man through sustainable development.
Enhancement in Crop Yields
To improve the crop yields, our government has taken many steps. The steps taken by the government has brought fruitful result as well. The following are the steps taken to improve the crop yielding:
Crop production and management: Our country is an agricultural country where the large population depends on the agriculture. Agricultural products are the sources of raw materials for industries. Thus, the proper crop production management is necessary, so that maximum benefit can be taken at the minimum cost. Govt has ensured the crop production management at various level.
Genetic manipulation of crops for higher yield: It is the incorporation of desirable character in the plants by various methods such as DNA recombinant technology, hybridization, mutation, etc. In this process, a gene of one organism is inserted into the DNA of other organism and thus a new organism is born with better features.
Crop protection management: Crops are in danger because of the pests, insects, moisture, mites, rodents, bacteria, etc. There are various methods that are used to protect the crops from the possible danger. Insecticides, pesticides and weedicides are used to kill insects, pests and weeds. The following are the techniques that are used to protect the crop from possible dangers:
Practice of crop rotation
Right time of sowing seeds
Using high quality and resistant variety of seeds
Nutrient Management
Nutrient is an important part of plant's food. Plants require nutrients for their growth that are supplied by air, water and soil. The nutrients required by the plants is categorized into two parts that are macro nutrients and micro nutrients. The deficiency of any nutrient in the plant body leads to diseases and affects the growth of the plant. There are natural ways to supply these nutrients to the plants but artificial ways are also used on a large scale to supply all the nutrients required by the more...
Verbal and Non-verbal Reasoning
Reasoning and logic skills are an integral part of a wide range of subjects of mathematics. These skills are very useful in our daily lives. In this chapter we will solve problems related to verbal and non-verbal reasoning.
Odd-One Out Types of Problems
In these types of problems, letters of the alphabet are classified into a group by applying a particular rule or pattern.
Example:
Choose the group of letters which is different from the others: BEI, MPT, RVZ, LOS
(a) BEI (b) MPT
(c) RV (d) LOS
(e) None of these
Answer (c)
Explanation:
\[B\underrightarrow{+3}\,E\underrightarrow{+4}\,I,\,\,M\underrightarrow{+3}\,P\underrightarrow{+4}\,T,\,\,R\underrightarrow{+4}\,V\underrightarrow{+4}\,Z,\,\,L\underrightarrow{+3}\,O\underrightarrow{+4}\,S\]
Clearly, RVZ is different from others.
Problems Related to Missing Number in the Series
In these types of problems, we have to find the missing number of the given series, where the given series follow a certain type of pattern.
Example:
Find the missing number in place of the question mark.
80 143 224 ? 440
(a) 420 (b) 258
(c) 228 (d) 323
(e) None of these
Answer (d)
Explanation:
So, it is clear that the 323 will replace the question mark.
Problems Related to Analogy
In these types of problems, we can understand the relationship between two figures, numbers or letters, which follow a certain rule or pattern.
Example:
Which shape will complete the second pair in the same way as the first pair?
(a) (b) (c) (d) (e)None of these
Answer (c)
Explanation: In the first pair the pin rotates \[{{90}^{o}}\] clockwise and rest of the part of figure rotates 90° anticlockwise and is then reversed at the new position.
Plant Cell
Different parts of a cell and their functions:
Plasma membrane - outermost covering of the cell which allows only selective substances to pass through it.
Cytoplasm - helps in exchange of materials between different cell organelles.
Endoplastic reticulum - helps in synthesis and transport of proteins and fats.
Mitochondria - oxidises food to release energy in the-from of ATP.
Golgi apparatus - helps in storage of secretory products.
Ribosomes - helps in protein synthesis.
Lysosome - helps in intra-cellular digestion.
Nucleus - helps in cell division and regulates all functions within the cell.
Nucleolus - helps in protein synthesis by forming and storing RNA.
Vacuoles - helps in storage of water and other substances.
Difference Between Diffusion and Osmosis
(b) 
(d) 
