## Saturday, 30 July 2011

### CBSE Class IX ( 9th) Science Chapter 4. Structure Of The Atom | Lesson Exercises

Question 1. Compare the properties of electrons, protons and neutrons.
 Electrons Protons Neutron Electrons are Negatively charged particles Electrons are present in outer shells with in an atom and  revolve around the nucleus in well-defined orbits or discrete orbits The mass of an electron is about 1/ 2000 times the mass of an hydrogen atom. A electron  is represented as 'e-' Protons are Positively charged particles. Protons are present in the nucleus of all atoms Number of protons determines the atomic number of an element The mass of a proton is taken as one unit and equals to neutron. A proton is represented as 'p+' Neutrons do not carry any charge and are neutral. Neutrons are present in the nucleus of all atoms, except hydrogen The mass of a neutron is taken as one unit and equals to that of proton. A neutron is represented as 'n'

## Chapter 1. Food - Where Does it come from?Chapter 2.Components of FoodChapter 3. Fibre to Fabric.

### CBSE Class IX ( 9th) Science | Chapter 3. Atoms And Molecules | Lesson Exercises

Question 1. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.

Mass of boron as given = 0.096 g
Mass of oxygen as given  = 0.144 g
Mass of sample as given   = 0.24 g
Percentage of boron by weight in the compound = (0.096 ÷ 0.24 )  x 100 = 40%
Percentage of oxygen by weight in the compound = (0.144 ÷ 0.24)  x 100 = 60%

## Sunday, 24 July 2011

### CBSE Class IX (9th) Science | Chapter 2. IS Matter Around Us Pure ? | Lesson Exercises

Question 1. Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea.

## Saturday, 23 July 2011

### CBSE Class IX (9th) Science | Chapter 1. MATTER IN OUR SURROUNDINGS | Lesson Exercises

Question 1. Convert the following temperatures to the celsius scale.
(a) 293 K (b) 470 K.

Answer : As we know 0° C =273.16 K. For convenience, we take 0° C = 273 K after rounding off the decimal.
To change a temperature on the Kelvin scale to the Celsius scale we have to subtract 273 from the given temperature

(a) 293 K =  293-273  = 20° C
(b) 470 K = 470-273   = 197° C

Question2. Convert the following temperatures to the Kelvin scale.
(a) 25°C (b) 373°C.

## Tuesday, 19 July 2011

### CBSE Class VIII (8th) Science | Chapter 7. CONSERVATION OF PLANTS AND ANIMALS | Lesson Exercises

Question 1. Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called  wildlife sanctuaries .
(b) Species found only in a particular area is known as Endemic species .
(c) Migratory birds fly to far away places because of  climatic changes.

Question 2. Differentiate between the following:
(a) Wildlife sanctuary and biosphere reserve
(b) Zoo and wildlife sanctuary
(c) Endangered and extinct species
(d) Flora and fauna

## Sunday, 17 July 2011

### CBSE Class VIII (8th) Science | Chapter 6. COMBUSTION AND FLAME| Lesson Exercises

Question 1. List conditions under which combustion can take place.

Answer :  Conditions under which combustion take places :

1. Some Fuel is  is required for combustion. During combustion a fuel substance reacts with oxygen to give off heat.The fuel may be solid, liquid or gas.
2. Oxygen in air  is essential for combustion. Combustion can not take place in the absence of air (oxygen).
3. For a combustion,  an inflamabe substance must be heated to its ignition tempreture. Ignition temperature is the lowest temperature at which a combustible substance catches fire.

### CBSE Class VIII (8th) Science | Chapter 5. COAL AND PETROLEUM | Lesson Exercises

Question 1. What are the advantages of using CNG and LPG as fuels?
Answer : CNG -  compressed natural gas, is stored under high pressure as compressed natural gas (CNG).  CNG is a very important fossil fuel because it is easy to transport through pipes. CNG is used for power generation. It is now being used as a fuel for transport vehicles because it is less polluting. It is a cleaner fuel. Similarly, LPG- Liquified Petroleum Gas is used as fuel for home and industry as it is less polluting and easy to transport and to use.

Question 2. Name the petroleum product used for surfacing of roads.
Answer : Earlier coal-tar a black, thick liquid which is obtained from coal processing, and is   a mixture of about 200 substances was mainly used for metalling or surfacing of the roads, now a days, bitumen, which is a petroleum product, is used in place of coal-tar for metalling or surfacing of the roads.

## Saturday, 16 July 2011

### CBSE Class VIII (8th) - Science | Chapter 4. MATERIALS : METALS AND NON-METALS | Lesson Exercises

Question 1. Which of the following can be beaten into thin sheets?
(a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen

Question 2. Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Answer : (c) Generally, metals are ductile.

# CBSE Class VIII (8th) - Science Chapter 3. SYNTHETIC FIBRES AND PLASTICS

Question 1. Explain why some fibres are called synthetic.

Answer : While natural fibres are obtained from plants and animals, synthetic fibres on the other hand, are  obtained by human beings from the chemical processing of petrochemicals. Petrochemicals when processed, results in different type of synthesised products like Petrol, Kerosene, Grease, Bitumen and polymers. Synthetic fibres are made from Synthetic polymers.  That is why these are called synthetic or man-made fibres.

## Thursday, 14 July 2011

### CBSE Class VIII (8th) - Science Chapter 2. MICROORGANISMS : FRIEND AND FOE | Lesson Exercises

1.Question:  Fill in the blanks:
(a) Microorganisms can be seen with the help of a  microscope.
(b) Blue green algae fix  nitrogen directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of  yeast.
(d) Cholera is caused by  pathogens.

(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen

## Tuesday, 12 July 2011

### CBSE Class VIII (8th) Science | Chapter 1. CROP PRODUCTION AND MANAGEMENT | Lesson Exercises

1. Question :  Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation
Solution:
(a) The same kind of plants grown and cultivated on a large scale at a place is called crop.
(b) The first step before growing crops is Preparation of the soil.
(c) Damaged seeds would  float on top of water.
(d) For growing a crop, sufficient sunlight and nutrients and water from the soil are essential.

## Monday, 11 July 2011

### Key Elements of a Democratic Government: Lesson 4 | Civics | Class VI (6th) Social and Political Life-1 | Lesson Exercises

1.Question. How would Maya's life be different in south Africa today?
If Maya lived in South Africa today she will enjoy equal rights to participate in the affairs of the government, she will have equal benefits and she will be protected by law. No injustice will be done  to her.

2.Question.What were various ways in which people participate in the process of government?
The people in a democracy participate in the process of government in the following ways:
(1) The people  elect their leaders by voting  in the elections, who represent them. They take decisions on behalf of the people.

## Friday, 8 July 2011

### Chapter 18. Wastewater Story : Science | CBSE Class VII (7th) | Lesson Exercises

1.Question : Fill in the blanks:
(a) Cleaning of water is a process of removing  pollutants.
(b) Wastewater released by houses is called   sewage.
(c) Dried _sludge is used as manure.
(d) Drains get blocked by  tealeaves, solid food remains, soft toys, cotton, and  sanitary towels .

2. Question : What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

### Chapter 17. Forests : Our Lifeline | Science | Class VII (7th) Lesson Exercises

1.Question :  Explain how animals dwelling in the forest help it grow and regenerate.
Answer : The wide variety of animals helps the forest to regenerate and grow.  In forest, plants produce food. All animals, whether herbivores or carnivores, depend ultimately on plants for food.Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes. This is said to form a food chain:
Grass→ insects→ frog→ snake→ eagle.

## Thursday, 7 July 2011

### CBSE Class VI (6th) Solved Exercises : Lesson 3. What is Government? | Civics - Social Studies (Our Pasts-1)

1.Question. What do you understand by the world 'government'? List five ways in which you think the government affects your daily life?
1.It protect our boundary and maintains peaceful relations with other countries.
2.Everyone should get enough to eat and there is no food shortage.
3.Look after the health of the people.
4.If there is natural disaster like Tsunami or an earthquake, it is the government that mainly organises aid and assistance for the affected people.
5.If there is a dispute or crime, the courts will provide justic.

### Water: A Precious Resource: Chapter 16 | Science |CBSE Class VII (7th) Exercises

Solutions :
1. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T)
(b) Water shortage is a problem faced only by people living in rural areas. (F)
(c) Water from rivers is the only source for irrigation in the fields. (F)
(d) Rain is the ultimate source of water. (T)

### Chapter 15 . Light | Science | CBSE Class VII (7th) | Lesson Exercises

Exercises : Solution
1. Fill in the blanks:
(a) An image that cannot be obtained on a screen is called a virtual image.
(b) Image formed by a convex  mirror  is always virtual and smaller in size.
(c) An image formed by a plane mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a real image.
(e) An image formed by a concave lens cannot be obtained on a screen.

## Wednesday, 6 July 2011

### Class VII (7th) Science | Lesson 14 : Electric Current and its Effects

Exercises : Solution
1. Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery

 Symbols for some electric circuit components

## Tuesday, 5 July 2011

### Class VII | Science | Lesson 13. Motion and Time

Exercises Solution
1. Classify the following as motion along a straight line, circular or oscillatory motion:
(i) Motion of your hands while running. :  - oscillatory motion
(ii) Motion of a horse pulling a cart on a straight road. :-  straight line motion
(iii) Motion of a child in a merry-go-round. : - circular motion
(iv) Motion of a child on a see-saw. :  -  oscillatory motion
(v) Motion of the hammer of an electric bell.- oscillatory motion
(vi) Motion of a train on a straight bridge : - straight line motion

## Sunday, 3 July 2011

### CBSE NCERT Class VI (6th) | History Social Studies (Our Pasts-1) | Unit Lesson : XII (12) : Buildings, Paintings And Books

Exercises: Solution :: Questions and Answers.

1.Question. Match the following.