SA-2

REVISION

1. How is sound produced?Sound is produced as a result of vibrations.2. Name the three properties of sound wavesThree properties are amplitude, time period and frequency.3. State the difference between the following.a) Time period and frequencyTime period-The time taken for the pendulum to complete one oscillation. It is measured in seconds.Frequency-The number of oscillations completed in one second. It is measured in Hertz.b) Music and noiseMusic- A sound which is pleasing to our ears. This is produced by regular and periodic vibrations.Noise-A sound which is not pleasing to our ears. This is produced by irregular and non-periodic vibrations.4. Explain how frequency determines the pitch.Different frequencies produces different sounds. If the sound produced has a high frequency, it is said to have high pitch and it is said to be shrill. If the sound produced has a low frequency, it is said to have low pitch and it is said to be gruff.5. Draw a neat labelled diagram and label the following parts.

6. What is timbre? On what factor does timbre upon?

The quality of sound is known as timbre. It depends upon source of sound.

7. Name the two factors on which speed of sound depends upon.

Physical state of matter and temperature.

8. How do humans produce sound?

Humans produce sound by the larynx which is located at the upper end of trachea. The larynx has two vocal cords with a narrow slit. The air from our lungs is pushed up to the larynx through trachea. When the air passes through the vocal cords it produces sound.

9. State the functions of the followinga) PinnaPinna-collects the sound waves and send it through ear canalb) Sensory hair cells in cochleaSensory cells – transmits the vibrations to the brain through auditory nerve for brain to register.

10. Label the parts in the given figure.

E

D

C

B

A

11. State one difference between infra sonic and ultra sonic range.

Infra sonic- The range of sound below 20 Hz.Ultrasonic-The range of sound above 20,000 Hz

12. What is echo?

Sound heard after reflection from a surface is called echo. Echo is used in SONAR. It is used by bats to avoid obstacles.

13. Expand SONAR. State the principle on which it works.Sound Navigation And Ranging. The principle used is the fact that the time taken for the sound to reach the obstacle from the source is equal to the time taken for it to return. It is used to estimate distances of mountains and buildings.

14. What are uses of SONAR?It is used to find the depth of seas, distance of sub marines, To estimate distances of mountains and buildings.

15. How do bats find their ways?Bats use the principle of echolocation. They emit ultrasonic waves which are reflected from the obstacles and help the bats in avoiding them.

16. Name the part that produces sound in the following instruments.

Air column Stretched membrane Strings17. How can you increase the frequency of the stringed instruments?a)shortening the length of the string.b) Strings should be thinc) Strings should be tightened

1.Differentiate between kharif and rabi crops.Kharif-These crops are grown between June/July and harvested in September. These crops require more water for growth.Rabi- These crops are grown between October and April. These crops does not require more water.

2. Name the techniques used for preparing soil.Ploughing and levelling

3. Seedlings should be equally spaced. Give reasonIt should be equally spaced as they should not compete for nutrients, water and sunlight.

4. Seeds should be sowed at right depth. Why?If the seeds are sowed close to the surface they will be eaten by birds and if sowed too deep they will be deprived of air.

5. State the advantage of using seed drill over broadcasting.The seeds are sowed at right depth and this method saves time and labour.

6. State any two disadvantages of using fertilizers over manures.Continuous use leads to soil and water pollution. Over use will make soil less fertile.

7. Define symbiosisA relationship in which both the organisms are mutually benefitted. Eg. Legumes and Rhizobium.

8. Explain drip system.This is a method by which water is allowed to fall drop by drop only on the roots of plants. This method is beneficial in water scarcity regions as there is no wastage of water.

9.What is sprinkler system. State its advantages.A method by which water is sprinkled over fields using sprinklers. It is advantageous for uneven land, land with scarcity of water and in sandy regions.

10.What are weeds? How are they harmful to crops?Weeds are unwanted plants that grow among the crops. They affect plant growth as they compete with crops for nutrients, space , water and sunlight.

11.How does sunflower and soya bean help in removing weeds?These plants release toxic substances which do not allow the growth of weeds.

12. Identify the implements used for weeding.

Trowel and harrow

13. Name the following.a) A bacterial diseases – Bacterial wilt of crops

b) two fungal diseases- Rust and smut of wheat and blight of potato

c) A viral disease – leaf curl in cotton.

d) Two insecticides- BHC and DDT

e) Two rodenticides- Warfin and Zinc phosphate

g) two fungicides- Copper salts and Sulphur salts

h) Two weedicides-2,4 D and MCPA

14. Grains should be dried in sun before storing. Why?

Grains should be dried as presence of moisture will promote microbial growth.

15. What is animal husbandry?The process of breeding and raising the animals on a larger scale is called animal husbandry.

16. Label the parts in the given figure.

1. What is combustion?The process of burning of a substance in the presence of oxygen is called combustion, Eg. Burning of coal.

2. What is ignition temperature?The lowest temperature at which a substance catches fire.

3. Name the three conditions essential for combustion.a) Substance must be combustible.b) Medium around the substance should combustion.c) Substance should be heated to ignition temperature

4. Observe the diagram given below and answer the question.a) Paper cup with water does not burn. Why?It is because the heat given by the flame is quickly transferred from the paper cup to water. As aresult the ignition temperature of the paper is not reached and hence paper cup does not burn.

b) Define calorific value of a fuel. Express it in its SI unitCalorific value of a fuel is the heat liberated when one gram of fuel burns completely in oxygen. SI unit of calorific value is J/Kg

5. Distinguish between spontaneous and rapid combustion.Spontaneous-When a substance catches fire unexpectedly and bursts into flame.eg. SodiumRapid- It occurs when a substance burns rapidly and releases large amount of heat. Eg. LPG

6. What type of substances will catch fire easily? Give reason.Substances with low ignition catch fire easily and burn. e.g.,. Sodium.

7. Give reasons:a) Water is not used to control fires involving electrical equipment.Water is a good conductor of electricity and hence will lead to electric shock.b)LPG is a better domestic fuel than wood.LPG is a better domestic fuel because it has high calorific value , does not release harmful gases and easy to transport.c) The flame appears orange yellow in the middle zone.It is because this zone undergoes partial combustion and the unburnt carbon particles gets extremely hot and starts glowing by emitting orange yellow light.8. Distinguish between primary and secondary fuel.Primary fuel- These fuels occur in the same form as they occur in nature. Eg. Wood.Secondary fuel- These are obtained from natural fuels by various physical and chemical processes. Eg. Coke.9. Label the parts in the given figure.

A

B

C

10. Why does the innermost zone of a flame appear greyish black?It appears greyish black as no combustion takes place due to the deficiency of oxygen due to which wax vapoursgets accumulated and appears greyish black.

11. Which of the following produces flame- kerosene or coal? Give reason.Flame is produced by those substances which vaporize on heating. Kerosene produces flame as kerosene oil vaporizes and rises upwards and burns to form a flame.

12. State one harmful effect of carbon monoxide and Sulphur dioxide.Carbon monoxide-CO will combine with haemoglobin and forms carboxyhaemoglobin. It decreases the oxygen carrying capacity of blood and causes headache, respiratory problems etc. Sulphur dioxide-This oxide dissolves in water and causes acid rain. Acid rain can be harmful to plants, monuments.

13. Explain soda acid fire extinguisher.a) The metallic cylinder contains saturated solution of sodium bicarbonate.b) A glass bottle containing sulphuric acid is tied to the knob of the metal cylinder.c) When the knob is struck the acid bottle breaks and the acid reacts with sodium bicarbonate forming carbon dioxide and other substances.d) Since carbondioxide is heavier than air it forms a blanket over the burning substance and cuts off the air supply

14. Which type of fire extinguisher is used for fire caused by flammable liquids and why?Carbon dioxide fire extinguisher is used for fire caused by flammable liquids because carbon dioxide is a non supporter of combustion.

1. Draw a neat labelled diagram of structure of an atom.

2.What is nuclear force?Nuclear force is a strong force by which the protons and neutrons are held tightly in the nucleus.

3. a) How is a glass rod gaining positive charge when rubbed with a silk cloth? Glass rod becomes positively charged because on rubbing glass rod loses negatively charged electrons to the silk cloth.

b) What is earthing?The process of a charged body coming in contact with an uncharged body and transferring its charges till the charges on both the sides becomes equal.

4.What is a lightning conductor?A long conducting rod connected to the highest point of a tall building to conduct the heavy electrical discharge during lightning to the earth.

5. Explain how lightning occurs.a) During thunderstorms, when layers of clouds rub against each other charges are developed.b) The positive charges stay at the middle and top of the cloud and negative charges to the bottom of the cloud.c) Due to the accumulation of negative charges at the bottom of the cloud, the positive charges also build up on the ground.d) As unlike charges attract the charges leap to the ground resulting in lightning.

6. Explain how earthquakes occur.a) It happens when two tectonic plates rub against each other. The surface where they slip is called fault. b) When the edges of tectonic plates release themselves, the energy radiates outwards in the form of seismic wavesc) The rupture begins at the epicenter, the point on the earths surface directly above the fault.d) These seismic waves shake the earth surface and causes damage to buildings, dams etc.

7. Label the parts marked. A

B

C

D

10. List any two uses of electroscope.a) It is used to detect whether the object possess charge or not.b) it is used to find whether the object is positively or negatively charged.

11.State any two differences between charging by conduction and charging by induction.Conduction- the process by which electric charges is produced in a conductor by bringing a charged object in contact with the uncharged body. The object attains similar charge as that of charged object.Induction-the process of charging an object by bringing it closer but without actual contact with the charged object. The object attains opposite charge as that of charged object.

12. Observe the figure and answer the questions.a) Identify the device and on what principle does it work.Electroscope-It works on the principle that like charges repel each other.

b) What happens to the gold leaf when a charged rod touches the disc of the electroscope?On touching the disc the charges are passed on to the gold leaves. Since like charges repelthe gold leaves will diverge.

1.What are asteroids and where are they located in the solar system?Very small, broken pieces of planets, made of rocks and metals which revolve around the Sun mainlybetween Mars and Jupiter

2. Identify the two constellation A and B given in the figureA-Ursa major/great bear/big dipper/ploughB-Ursa minor/little dipper

3. State one difference between meteors and meteorites. Meteors-A small piece of rock from outer space that enters the Earth’s atmosphere and glows as a streak of light as a result of friction with air. Meteorites-A meteoroid that does not burn completely and falls to the Earth’s surface.

4. What are comets and when do they become visible to us? Very small celestial bodies made of gas and dust which revolve around the Sun in highly elliptical orbits and become visible only when they come close to sun.

5.State any two uses of artificial satellites. -study the universe/forecast weather/transfer telephone calls/assist in navigation ofships/monitor crops/support military activities.

6.Identify the constellation given alongside.-Orion

1. Draw a neat labelled diagram to show reflection of light through a plane mirror.

2. Distinguish between regular and irregular reflection.Regular- takes place when he light is reflected from a smooth and highly polished surface.Irregular- takes place when light falls on a uneven or rough surface.

3.State the laws of reflection.

4.State two differences between concave and convex lensConcave- Thin in the middle and thick at the edges. It diverges the light rays passing through it.Convex- Thick in the middle and thin at the edges. It converges the light rays passing through it.

5.what is power of accommodation?The ability of the eye lens to self adjust its focal length.

6. Label the parts in the given figure.

A

B

C

D

E

G

F

7.State the function of the following parts.a) Iris-

It controls the size of the pupil through which the light rays enter the eye ball.

b)Eye lens-

It focuses the light passing through it on the retina.

c)Ciliary muscles-

It holds the lens in its position. It helps in adjusting the focal length of the lens.

d)Optic nerve-

The electrical signals generated on the retina are transferred to the brain through the optic nerve for interpretation so that the objects can be seen.

11.If a ray falling on a plane mirror forms an angle of 60̊ with the mirror, what will be the angle of reflection?Angle of reflection = 90-60 = 30 ̊

12.List the rules that are that are followed by light during refraction.

13.Diagramatically represent concave and convex lens.

14.What is cataract and how can it be treated?It is an eye defect that generally occurs during the old age. The eye lens becomes cloudy and the patient might his/her eye sight. It can be treated surgically by replacing the diseased lens with an artificial lens.

15. What is persistence of vision?This is a phenomenon where the brain remembers the image for 1/16th of a second even after the object is removed from vision. This phenomenon is utilized in making of motion pictures.

1.Industrial effluents affect human body. Justify.Industrial effluents contains specific chemical compounds such as lead, cadmium and copper. These can affect nervous system and cause skin infections when they enter human body.

2. What is potable water?Potable water is the water which is fit for drinking.

3.What is eutrophication?

4. What are electrolytes and non electrolytes?Electrolytes- liquids that allow electric current to flow through. Eg. Tap water, Sulphuric acid.Non electrolytes- Liquids that do not allow electric current to flow through them..Eg. Distilled water, sugar solution

5. 5.Why is tap water a good conductor of electricity?Tap water is a good conductor of electricity because of the presence of dissolved salts in the water which increases the conductivity.

6. Observe the experimental set up and answer the questions that follows.a) Name the parts labelled.

b) What is an electrolytic cell?A device containing two electrodes in contact with an electrolyte that brings about a chemical reaction when connected to a battery.

c)Define electrolysis.The process of passing electric current through a liquid to bring about a chemical change.

d)How is it possible to get hydrogen and oxygen from water

e) Name one application of electrolysis.-electroplating.

7. What is the importance of electroplating?- To make articles attractive.- To protect articles from corrosion.

8. Observe the diagram and answer the questions given below.a)Identify A and B.A- Cathode B- Anode

b)What is collected at B when electric current is passed through the electrolytic cell?Chlorine gas is collected at anode.

c) Why does the surface of A acquires red colour?The surface of cathode acquires reddish deposit due to the deposition of copper.

d)Why the does the colour of copper chloride solution fades off after theelectric current is passed through?The bright blue colour of copper chloride starts fading because when electric current is passed through copper chloride solution it splits into copper and chlorine.

1. What is biodiversity?Biodiversity – means the variety of plants and animals that live in a particular region or habitat and interacting with one another.

2. Name the different threats to biodiversity.Deforestation, Overexploitation, Climatic change.

3.Why are endemic species more vulnerable to extinction?They are more vulnerable to extinction as they are localized in small part of the world. E. Lion tailed macaque.

4. Name two sanctuaries.-Bharatpur bird sanctuary, Chilka bird sanctuary.

5.What is Red Data Book?It is a record of all endangered plants, animals and fungi.

6. List the two goals of Red Data Book.1) To provide status of species and subspecies.2) To draw attention for the threatened biodiversity.

7. what are the consequences of deforestation?The various consequences are soil erosion, loss of bio diversity, floods, reduced rainfall etc.

8.What is poaching?Illegal hunting of animals for hide, bone or tusk. Poaching leads to loss of biodiversity.