A:
Push is the press on an object that can change the shape and direction of motion of an object.
A:
Natural causes of deforestation are fire and severe droughts.
A:
The fibers which are made by human beings are called synthetic fibres.
A:
When one body roll over the surface of another body, the frictional force that comes into paly between the two surface is called the rolling friction.
A:
Cotton is a natural polymer.
A:
Sound is produced by vibration of the objects.
A:
Microorganisms are the living organisms which can not be seen with unaided eyes. They have a high degree of adaptability and can survive in all kinds of environment, like hot springs, ice cold water, saline water, desert soil, marshy land and even inside the human body.
A:
PCRA is Petroleum Conservation Research Association.
A:
The chemical reaction (decomposition) of an electrolyte (conducting liquid) into its components when electricity is passed through it is called electrolysis.
A:
Sowing is the process of planting seeds.
A:
Metals: Copper.
Non-Metals: Sulphur.
A:
A person swims due to action and reaction forces. He pushes the water with some force in the backward direction with his hand which is called an action and water pushes the person in the forward direction with equal force which is called a reaction.
A:
Harvesting is the process of gathering or cutting mature crops from the fields. And the process by which grain seeds are seperated from harvested crop are called threshing.
A:
Nylon is used in many articles, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains and parachute ropes.
A:
When an electric current is passed through a wire, the current carrying wire behaves like a magnet. When a magnetic compass is brought near it, the needle shows deflection. This effect is called magnetic effect of electric current.
A:
- Help in the formation of antibiotics.
- Help in the decomposition of dead organic matter.
A:
Aluminium reacts with the citric acid present in the lemon. Hence, lemon pickles can't be stored in aluminium vessels.
A:
The three ways of minimizing friction between two surfaces are
(i) Polishing of the roughened surfaces
(ii) Use of grease and lubricants
(iii) Use of ball bearings between moving surfaces of machine parts
A:
Steps that can be taken to conserve forests are:
- Reuse and Recycling of paper.
- Strict laws for preventing deforestation.
- Reforestation.
A:
Due to natural processes, like flooding, dead plants got buried under the soil. As more soil deposit over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called Carbonisation. As it was formed from the remains of vegetation, coal is also called a fossil fuel.
A:
(i) Light travels faster than sound. Velocity of light is 3 x 108 m/s while of sound is 330 m/ s. So, light covers the distance faster than sound.
(ii) Supersonic jets fly faster than the speed of sound and hence, they cannot be heard when they approach us but a boom is heard after it passes away.
A:
Forests are essential because they:-
• form different types of ecosystems and biomes and create an environment which affects various types of animals and plants.
• keep the environment cool by regulating transpiration and precipitation.
• have aesthetic, cultural and spiritual importance.
A:
Petoleum is a black oily liquid. Its fractional distillation yields a range of combustible fuels, petrochemicals, and lubricants. These petrochemicals are used in the manufacture of detergents, fibers (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Also, hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).
Hence, petroleum is called ‘black gold’ due to its great commercial importance and appearance.
A:
Differences between musical sound and noise are: | Musical sound | Noise |
| 1. It has a pleasing effect on the ears. 2. It is produced by regular vibrations. 3. Presence of this sound in the surroundings does not create health related problems like hypertension, anxiety, etc. | 1. It does not have a pleasing effect on the ears. 2. It is produced by irregular vibrations. 3. Presence of noise in the surroundings create health related problems like hypertension, anxiety, etc. |
A:
The process of depositing a thin layer of a desired metal over another metal object with the help of electric current is called electroplating.
For electroplating a steel spoon with silver, a solution of silver, i.e. AgNO3 is taken as the electrolyte. The spoon and a pure silver bar are dipped into the electrolyte and connected to the negative and positive terminals of a battery respectively. When electric current is passed through the silver nitrate solution, it dissociates due to chemical effect of electric current. The positively charged silver ions move to the negative electrode (spoon) and form a deposit of silver on it and thus the spoon is silver plated.
A:
Useful effects:
1. They help in formation of curd, cheese, etc.
2. Convert the fruit juices into vinegar and wines.
3. Decompose the complex organic material into simple inorganic molecules.
4. Help in tanning of the leather.
5. Some help in fixing atmospheric nitrogen.
6. Some of them present in the intestine help in the process of digestion.
Harmful effects:
1. They cause a large variety of diseases in plants, animals and human beings.
2. They spoil food items as well as cloths, leather, etc.
A:
Properties of synthetic fibers :
i) cheap and affordable.
ii) wrinkle free .Hence, they do not need ironing. They do not need maintenance like natural fibers.
iii) dry quickly.
iv) more elastic as compared to natural fibers.
v) more durable as compared to natural fibers.
vi) do not shrink.
A:
When two surfaces slide over each other, the force, which opposes the motion of one body over the other, is called force of friction.
Disadvantage of frictional forces are seen as:
(i)Wear and tear of objects coming in contact. Example: soles of shoes and tyres of vehicles.
(ii)Loss of energy as heat. Example: Machine parts get heated up and lead to wear and tear.
(iii)Loss of energy to overcome friction. Example: Wastage of fuel in machinery.
A:
| Fertilizers | Manures |
| 1. Fertilizers can be organic (composed of organic matter), or inorganic (made of simple, inorganic chemicals or minerals). | Manure is a natural substance obtained by the decomposition of cattle dung, human waste and plant residues. |
| 2. A fertilizer is prepared in factories. | As it is naturally obtained so it can prepare in fields. |
| 3. A fertilizer does not provide any humus to the soil. | Manure provides a lot of humus to the soil. |
| 4. Fertilizers are very rich in plant nutrients like nitrogen, phosphorus and potassium. | Manure is less rich in plant nutrient in comparison to fertilizers. |
| 5. Fertilizers are compounds given to plants to promote growth. | Manures enhances the water holding capacity of the soil and improves the texture of soil. |
A:
Three disadvantages of friction between the parts of a machine are:
1. It wastes energy.
2. It wears out the rubbing surfaces of the machine parts.
3. It causes heating.
Engineers always try to reduce friction. Two ways of reducing friction are oiling and using ball bearings or roller bearings.
By oiling: It prevents direct contact between the surfaces by forming a film between them.Due to this, the surfaces move easily.
By using ball bearings: Ball bearings come in many shapes and sizes and are used to reduce friction especially when a rod rotates inside a hole, as in a bicycle wheel. They are used between the wheel hub and the axles of bicycle due to which the friction reduces considerably. Most of the time, they are used in the machine having moving parts.
A:
Push is the press on an object that can change the shape and direction of motion of an object.
A:
Natural causes of deforestation are fire and severe droughts.
A:
The fibers which are made by human beings are called synthetic fibres.
A:
When one body roll over the surface of another body, the frictional force that comes into paly between the two surface is called the rolling friction.
A:
Cotton is a natural polymer.
A:
Sound is produced by vibration of the objects.
A:
Microorganisms are the living organisms which can not be seen with unaided eyes. They have a high degree of adaptability and can survive in all kinds of environment, like hot springs, ice cold water, saline water, desert soil, marshy land and even inside the human body.
A:
PCRA is Petroleum Conservation Research Association.
A:
The chemical reaction (decomposition) of an electrolyte (conducting liquid) into its components when electricity is passed through it is called electrolysis.
A:
Sowing is the process of planting seeds.
A:
Metals: Copper.
Non-Metals: Sulphur.
A:
A person swims due to action and reaction forces. He pushes the water with some force in the backward direction with his hand which is called an action and water pushes the person in the forward direction with equal force which is called a reaction.
A:
Harvesting is the process of gathering or cutting mature crops from the fields. And the process by which grain seeds are seperated from harvested crop are called threshing.
A:
Nylon is used in many articles, such as socks, ropes, tents, toothbrushes, car seat belts, sleeping bags, curtains and parachute ropes.
A:
When an electric current is passed through a wire, the current carrying wire behaves like a magnet. When a magnetic compass is brought near it, the needle shows deflection. This effect is called magnetic effect of electric current.
A:
- Help in the formation of antibiotics.
- Help in the decomposition of dead organic matter.
A:
Aluminium reacts with the citric acid present in the lemon. Hence, lemon pickles can't be stored in aluminium vessels.
A:
The three ways of minimizing friction between two surfaces are
(i) Polishing of the roughened surfaces
(ii) Use of grease and lubricants
(iii) Use of ball bearings between moving surfaces of machine parts
A:
Steps that can be taken to conserve forests are:
- Reuse and Recycling of paper.
- Strict laws for preventing deforestation.
- Reforestation.
A:
Due to natural processes, like flooding, dead plants got buried under the soil. As more soil deposit over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called Carbonisation. As it was formed from the remains of vegetation, coal is also called a fossil fuel.
A:
(i) Light travels faster than sound. Velocity of light is 3 x 108 m/s while of sound is 330 m/ s. So, light covers the distance faster than sound.
(ii) Supersonic jets fly faster than the speed of sound and hence, they cannot be heard when they approach us but a boom is heard after it passes away.
A:
Forests are essential because they:-
• form different types of ecosystems and biomes and create an environment which affects various types of animals and plants.
• keep the environment cool by regulating transpiration and precipitation.
• have aesthetic, cultural and spiritual importance.
A:
Petoleum is a black oily liquid. Its fractional distillation yields a range of combustible fuels, petrochemicals, and lubricants. These petrochemicals are used in the manufacture of detergents, fibers (polyester, nylon, acrylic etc.), polythene and other man-made plastics. Also, hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).
Hence, petroleum is called ‘black gold’ due to its great commercial importance and appearance.
A:
Differences between musical sound and noise are: | Musical sound | Noise |
| 1. It has a pleasing effect on the ears. 2. It is produced by regular vibrations. 3. Presence of this sound in the surroundings does not create health related problems like hypertension, anxiety, etc. | 1. It does not have a pleasing effect on the ears. 2. It is produced by irregular vibrations. 3. Presence of noise in the surroundings create health related problems like hypertension, anxiety, etc. |
A:
The process of depositing a thin layer of a desired metal over another metal object with the help of electric current is called electroplating.
For electroplating a steel spoon with silver, a solution of silver, i.e. AgNO3 is taken as the electrolyte. The spoon and a pure silver bar are dipped into the electrolyte and connected to the negative and positive terminals of a battery respectively. When electric current is passed through the silver nitrate solution, it dissociates due to chemical effect of electric current. The positively charged silver ions move to the negative electrode (spoon) and form a deposit of silver on it and thus the spoon is silver plated.
A:
Useful effects:
1. They help in formation of curd, cheese, etc.
2. Convert the fruit juices into vinegar and wines.
3. Decompose the complex organic material into simple inorganic molecules.
4. Help in tanning of the leather.
5. Some help in fixing atmospheric nitrogen.
6. Some of them present in the intestine help in the process of digestion.
Harmful effects:
1. They cause a large variety of diseases in plants, animals and human beings.
2. They spoil food items as well as cloths, leather, etc.
A:
Properties of synthetic fibers :
i) cheap and affordable.
ii) wrinkle free .Hence, they do not need ironing. They do not need maintenance like natural fibers.
iii) dry quickly.
iv) more elastic as compared to natural fibers.
v) more durable as compared to natural fibers.
vi) do not shrink.
A:
When two surfaces slide over each other, the force, which opposes the motion of one body over the other, is called force of friction.
Disadvantage of frictional forces are seen as:
(i)Wear and tear of objects coming in contact. Example: soles of shoes and tyres of vehicles.
(ii)Loss of energy as heat. Example: Machine parts get heated up and lead to wear and tear.
(iii)Loss of energy to overcome friction. Example: Wastage of fuel in machinery.
A:
| Fertilizers | Manures |
| 1. Fertilizers can be organic (composed of organic matter), or inorganic (made of simple, inorganic chemicals or minerals). | Manure is a natural substance obtained by the decomposition of cattle dung, human waste and plant residues. |
| 2. A fertilizer is prepared in factories. | As it is naturally obtained so it can prepare in fields. |
| 3. A fertilizer does not provide any humus to the soil. | Manure provides a lot of humus to the soil. |
| 4. Fertilizers are very rich in plant nutrients like nitrogen, phosphorus and potassium. | Manure is less rich in plant nutrient in comparison to fertilizers. |
| 5. Fertilizers are compounds given to plants to promote growth. | Manures enhances the water holding capacity of the soil and improves the texture of soil. |
A:
Three disadvantages of friction between the parts of a machine are:
1. It wastes energy.
2. It wears out the rubbing surfaces of the machine parts.
3. It causes heating.
Engineers always try to reduce friction. Two ways of reducing friction are oiling and using ball bearings or roller bearings.
By oiling: It prevents direct contact between the surfaces by forming a film between them.Due to this, the surfaces move easily.
By using ball bearings: Ball bearings come in many shapes and sizes and are used to reduce friction especially when a rod rotates inside a hole, as in a bicycle wheel. They are used between the wheel hub and the axles of bicycle due to which the friction reduces considerably. Most of the time, they are used in the machine having moving parts.
