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Sunday, May 10, 2015

Microorganisms friend and Foe class 8 Solved Questions answer

Q. Viruses are considered as being on the border line between living and non-living organisms,Why?
Ans: Viruses is nonliving out side living cells but grows and multiplies inside living cell so,viruses are considered as being on the border line between living and non-living organisms.The study of viruses is called Virology.

Questions: What does Sargasso Sea woe its name to?
Ans: Sargasso Sea woe its name to Sargassum, a particular sea weeds that grow abundantly in sea. Sailor avoids this sea as their boat stuck in the tangled mass of seaweeds.

Questions: What are the difference between the cell of bacteria and the cell of other living body?
Ans: The difference between the cell of bacteria and the cell of other living body are

(i) Cell wall is not made up of cell wall

(ii) Do not have nucleus

(iii)Does not have membrane bound organelles

Questions: Do red and brown algae have chlorophyll?
Ans: Yes, red and brown algae have pigment of colour which cover the colour of chlorophyll and make them appear red brown or yellowish

Questions: Name a protozoon which can photosynthesize?
Ans: Euglena contain chlorophyll and can photosynthesise, lack of cell wall

Questions: How do bacteria reproduce?
Ans: Bacteria reproduce by binary fission

Question: What are antibiotics? What precautions must be taken while taking antibiotics?
Answer: Antibioticsare medicines produced by certain micro­organisms to kill other diseasecausing micro­organisms. These medicines are commonly obtained from bacteria and fungi. Streptomycin, tetracycline, penicillin, etc. are common antibiotics.

Precautions to be taken while using antibiotics:

(i) Antibiotics should be taken under the supervision of a well qualified doctor.
(ii) Course (intake) of antibiotics should be completed as per the prescription given by the doctor.
(iii) Antibiotics should be taken in the right amount and at the right time. A wrong dose of antibiotics makes the drug ineffective. Also, excessive consumption of drugs may kill the useful bacteria present in our body.

Question: Why do bacteria classified under plants?
Ans: The cell of bacteria is covered by protective layer called cell wall. This is the reason because which bacteria classified under plants.
Sometime bacteria passing through adverse condition, they developed additional protective wall called cyst around them. The process of the formation of cyst is called encystment.

Question: Which protozoan exhibits both characteristics of plants and animals?
Ans: Euglena

Question: what are retroviruses?
Ans: viruses lack of cellular structure like cytoplasm and organelles. they only consist of DNA and RNA encompassed by a protein layer called capsid. viruses carring RNA are called retroviruses.

Question: what are chemosynthetic bacteria
Ans: Bacteria that obtain energy required for metabolic processes from exothermic oxidation of inorganic or simple organic compounds without the aid of light.

Question: what are viruses that infect bacteria

Ans: Bacteriophage is a virus that infects and replicates within a bacterium.

Question: Why is it difficult to prepared vaccine for diseases caused by viruses?
Ans: viruses are difficult to be grown in an artificial nutrient medium . Hence, it difficult to prepared vaccine for diseases caused by viruses.

Question: Why do some bacteria and fungi considered as natural purifier?
Ans: some bacteria and fungi decompose the dead organic matter and therefore called natural purifier

Question: Why are legumes plants considered important in crop rotation?
Rhizobium bacteria present in the root nodules of legumes plants fix the atmospheric nitrogen ad maintain the fertility of soil.

Usefull links by jsuniltutorialMicroorganisms- : 

  • Objective Questions 
  • Microorganisms- : Notes 
  • Microorganisms- : MCQ 's 
  • Microorganisms : Test Paper-1 
  • Microorganisms : Test Paper -2 
  • Basic science solved Questions 

Saturday, May 9, 2015

Heat and Temperature Basic science Class 7 solution

Solution of chapter Heat and Temperature Basic science Class 7

A. Answer these question in not more than 20 words
1. Give an example to show that heat is a form of energy?

Answer: When we heat a pan of water, the water boils and at its temperature rises. The energy for this rise in temperature comes from heat. This shows that heat is a form of energy.

2. What is temperature? Name the scale used to measure it?

Answer: Temperature of a body is the measure of the hotness or coldness of the body. Celsius and Fahrenheit are the scales used to measure temperature.

Thermometry is branch of physics which deals with the measurement of temperature.

3. If hotness and coldness of a body is relative, how do we measure its degree of hotness?
Answer: We measure the degree of hotness or coldness of a body by measuring its temperature and comparing with standard temperature scale.

4. Mention three things that heat causes in substance?
Answer: Following are the three changes that heat can cause in any substance:

(a) Heat can change the temperature of a substance.

(b) Heat can expand a substance.

(c) Heat can change the state of a substance.

5. How does heat travel in spoon from hot boiling soup
Answer: Heat travel through the spoon by conduction.

6. How is it that we hold a match while it is burning?
Answer: We can hold a match while it is burning because wood is a bad conductor of heat and does not transfer of heat through conduction hand

7. How does turning on heater in room make the whole room warm?
Answer : Heat from the heater transfers to the whole room through radiation that rises the temperature of the whole room.

8. How does heat from the sun reaches the earth?
Answer: Heat from the sun reaches the earth by the process of radiation

9. Mention one similarity between heat and light?
Answer: Heat and light, both are forms of energy and both travel in a straight line

10. When two bodies are in contact, heat flows from hotter to colder bodies. When does heat stop flowing?

Answer: The flow of heat from the hotter body to the colder body will stop when the temperatures of the two bodies become equal.

B.Answer these question in not more than 40 words
1. Distinguish between the Celsius and Fahrenheit scale

Answer:

Celsius Scale

The lower fixed point is 0°C.

The upper fix point is 100 C.

The fundamental interval is divided in 100 equal parts and each part is called 1°C (one degree Celsius).

It is introduced by Celsius, is usually used in scientific laboratories.

Fahrenheit Scale

The lower fixed point is 32F.

The upper fix point is 212 F.

The fundamental interval is divided into 180 equal divisions. Each division is called one degree Fahrenheit. (1°F).

It is suggested by Gabriel Fahrenheit, is usually used in clinical and meteorological purposes.

2. How does heat travel through water on heating?
Answer: Convection is a process through which heat travels through the water. When water is heated, the water became lighter. Hot water rises up. The cold water from the sides moves down towards the source of heat This water also gets hot and rises and water from the sides moves down. This process continues till the whole water gets heated. This mode of heat transfer is known as convection

3. what happen to the radiant heat when fall on the body? What does the absorption of radiant heat by a body depends on?

Answer: When radiant energy falls on an object, some of its part is absorbed by the object and some is reflected by the object.

Absorption of the radiant energy depends upon the following: (i) The colour of the object. (ii) Nature of the surface.

4. (a) Mention difference between transfer of heat by conduction and that of radiation?
    (b) Mention difference between transfer of heat by conduction and that of convection?

Answer :

(a) Conduction: Flow of heat through a medium occurs without the movement of the material.

Radiation: Flow of heat occurs without the help of any material medium.

(b) Conduction: Flow of heat through a medium occurs without the movement of the medium.

Convection: Flow of heat through a medium occurs with the movement of medium.

C. Answer these question in not more than 100 word
1. Explain how land and see breeze originated?

Answer: Sea takes longer to get heated than the land. So, the land is hotter than the sea during the day. The air in contact with the land becomes hot and rises and the cooler air above the sea moves towards the land to replace the hot air. This movement of air from sea towards the land is called sea breeze.

After sunset, the land cools faster than the sea. The air above the sea is warmer than the air above the land. Air above the sea rises and the cooler air above the land moves towards the sea. This is called land breeze.

2. How would you demonstrate to a friend that gases expand on heating?
Answer: The following experiment explains that a gas expands when it is heated: Take a balloon and a glass bottle. Fit the balloon to the mouth of a glass bottle. Place the bottle in a pan of water. Put the pan over a gas flame and heat it.

It is now seen that the balloon gets inflated as the air inside the bottle becomes warm and expands. Also when the bottle is cooled, the balloon gets deflated as the air inside the bottle gets cooler. This shows that gas expands when it is heated.

3. (a) Why does It is better to wear light shades in summer?

(b) Why do two thin sweaters feel warmer than one thick sweater?

(c) ) Why do handles of utensils are made up of plastic while their handle are made up of plastic?


Answer: (a) It is better to wear light shades in summer because light shades absorb less heat.

(b) Two thin sweaters feel warmer than one thick sweater because the air trapped between the two sweaters acts as an insulator of heat. It does not allow the heat from our body to escape easily.

(c) Handles of utensils are made up of plastic because plastic is a poor conductor of heat. Therefore, heat will not travel through the plastic and the handles will remain cool during cooking. This saves our hand from getting injured from the heat.

Metal on the other is a conductor of heat, which helps in transferring heat from the burner flame to the food and helps in cooking the food.

D. Choose the correct options
1.(a) does not require any medium

2. (b) some metals conduct heat better than others

3. (b) so that the level of mercury does not fall as soon as the thermometer is taken out of the mouth

4. (c) poor absorber and good reflector of heat

5. (b) good absorber and good emitter of heat

6. (d) evaporation

E. Say true and false
Answer :

1. True. Water boils at 212 F.

2. False. Clinical thermometer has kink in the capillary tube.

3. True. Liquid expands more than solid.

4. True. The heat from the sun reaches to the earth through radiation.

5. False. Solid is a good conductor of heat than liquid and gas.

6. True. Heat flows in convection by the movement of the substance.

7. False. Transfer of heat by radiation do not need contact between a hot and a cold body.

8. True. Air is a poor conductor of heat.

Monday, April 27, 2015

Learnwell science class 8 chapter force and pressure n Friction

High order thinking skill [HOTS Questions]

Learnwell science class 8

1. Why are women advised not to wear high heeled shoes?

Ans: High heeled shoes do not distribute weight of body over the surface of and therefore women may fall on the ground due to less grips on ground. This is why women are advised not to wear high heeled shoes.

2. It is more difficult to pull boat on the beach than on the water?

Ans: Liquid and gases exert lesser friction as compared to solid surfaces. Therefore, boat on the beach experience more friction than on the water. Thus, it is more difficult to pull boat on the beach than on the water.

3. How are you able to drink juice using a straw?

Ans: When we suck air from straw the air pressure in the straw decreases that is enough to pull the juice. Air pressure pull the juice to move up inside the straw into our mouth .

4. Why is the tip of sewing needle sharp?

Ans: The sharp tip of sewing needle sharp distributes force over less are so that more pressure created on the clothes. This makes work with needle easier.

5. Why are powder sprinkled on the carom board before playing?
Ans: Powder sprinkled on the carom board before playing to reduce friction between coins and surface of carom board.

6. Why does a woman apply soap solution on their hand to put on bangles?
Ans: A woman apply soap solution on their hand to reduce friction so that it became easier to put on bangles .

7. Does the shoes having spikes on their sole help in making better grip on ice?
Ans: Yes, spikes increase friction and help to have better grip on ice.

8. Will a match stick catch fire when it is rubbed against cemented wall?

Ans: Yes. A match stick catches fire when it is rubbed against cemented wall because force of friction raises the temperature of match stick head.

9. What would happen if there is no friction?

Ans: Friction is the force that opposes the motion of every object. So if there is no friction then, there would be nothing to stop a moving object, and it would continue to move forever

10. Machine parts are oiled occasionally?

Ans: Lubricant like oil and grease form layer between the two moving surfaces so that they cannot directly rub each other. This make the movement smoother.

Learnwell science class 8 chapter Synthetic fiber   View or Download

For more questions answer: www.jsuniltutorial.weebly.com/ 

Sunday, April 19, 2015

Matter in our surrounding solved questions class9 Step-01

Matter in our surrounding solved questions


Q. 1. What is a matter?

Answer: Anything that occupies space and has mass is called a matter. For example:- Chalk, Milk, Sugar etc.

Q. 2. Sodium chloride and sugar have same appearance. Are they same or different?

Answer: They have different physical and chemical properties. So, they are different

Q. 3. All substances around us are alike. How?

Answer: All substances can occupy space and have weight.

Q. 4. How can we say that air is a matter?

Answer: Air occupies space and have weight. Hence air is a matter.

Q. 5. State the characteristics of matter?

Matter has mass, weight and occupies space.

Q. 6. What are the intensive properties of matter?

Answer: Density, colour, melting point, boiling point, refractive index etc. are the intensive properties of matter as it does not depend upon the amount of matter contained in it

Q. 7. What are the extensive properties of matter?

Answer: The properties which depends upon the amount of matter contained in a substance is called extensive  properties of matter. For example mass, weight, volume, energy etc.

Q. 8. State the characteristics of particles of matter.

Answer: 

(i) There is enough space between the particles of matter.

(ii) The particles of matter are continuously moving about their mean position.

(iii) The particles of matter attract each other.

Q. 9. What is the effect of temperature on a matter?

Answer: Particles of matter posses kinetic energy. As the temperature rises, kinetic energy increases.

Q. 10. The smell of hot sizzling food reaches us several metres away. Why?

Answer: As the rate of diffusion increases with the increase in temperature.

Q. 11. What is diffusion?

Answer: When two gases are mixed, their molecules mix with each other due to their speed and random  motion. This phenomenon is known as diffusion

Q. 12. If a bottle of perfume is opened in one corner of a room, it immediately spreads throughout the room. Why?

Answer: The molecules of a gas are free to move in a chaotic motion at a greater speed throughout the vessel  in which it is contained. When the bottle of perfume is opened in one corner of the room, the molecules of perfume move at random motion in all direction and mix with the molecules of air and  reaches us

Q. 13. Name the three states of matter with examples.

Answer: The three states of matter are:

(i) Solid: - A solid has definite shape and volume.Example – wood, metal, rubber.

(ii) Liquid: - A liquid has definite volume and its shape is the shape of the container.
Example  water, oil, petrol.

(iii) Gas: – A gas has neither a definite volume nor a definite shape.        
Example – air, hydrogen, oxygen.

Q. 14. State the characteristics of solids.

Answer: Solids are rigid. The molecules of solids are packed closely and remain fixed at their position. The  molecules of solids are packed closely and remain fixed at their position. The force of attraction  between the molecules are very strong and hence they resist any change in their shape or volume.

Q. 15. What are the characteristics of liquids?

Answer: Liquids have definite volume but not a definite shape. They take the shape of a container in which  they are stored. The molecules have weaker force of attraction than solids, and hence can flow easily.

Q. 16. What are the characteristics of gases?

Answer: Gases have neither definite volume nor definite shape. The molecules have very weak force of  attraction and low density. They can be compressed to liquid state and flow in any direction.

Q. 17. What are fluids?

Answer: Substances having tendency to flow are called fluids. Liquids and gases are fluids.

Q. 18. Give one similarity between a liquid and a gas and one dissimilarity.

Answer:

Similarity: - Both liquids and gases are fluids and they take the shape of the container.

Dissimilarity: - A gas can be compressed easily to a desired volume. A liquid can not be compressed easily. A small volume of gas occupies the whole space of the container. But the volume of liquid is  fixed. A large volume of gas can be stored in a container of very small volume.

Q. 20. What property of gas is utilized when natural gas is supplied for vehicles.

Answer: High comprehensibility of gas is utilized and compressed it for supply for the vehicles in the name of  CNG.

Q. 21. What are ‘intermolecular forces’? How are these related to the three states of matter ?

Answer:  The force operating between the atoms or molecules of a matter is called intermolecular force. The  intermolecular force in solid are strong. This keeps the constituent particles very close to each other. 

Due to this solids are rigid and incompressible. This also give ordered arrangement of the particles 
giving regular geometrical shape to the solid.

In liquid, inter molecular force is weak to give definite shape.

In gas, intermolecular force is negligible and so its constituents particles are free to move and occupy 
the available space.

Q. 22. Separate the following substances in groups of high and low intermolecular force:Ice, sulphur 
vapour, nitrogen, sugar, copper, air, salt, plastic.

Answer:

High intermolecular forces :-    Ice, sugar, copper, salt, plastic

Low intermolecular forces :-     Sulphur vapour, nitrogen, air

Q. 23. Which of the following substances you expect strongest and in which weakest intermolecular 
force:  Water, alcohol, sugar, sodium chloride, carbon dioxide.

Answer: 

Sodium chloride – Strongest

Carbon dioxide – Weakest

Q. 24. Why are gases compressible but liquids not ?

The molecules of a gas are separated very far and there is a lot of empty space between them. Hence 
gases can be compressed easily. In liquids molecules are closer to each other and can be brought 
further closer only under very high pressure.

Q. 25. Compare the process of boiling and vaporization.

Answer: 
 Boiling                                                              
Vapuorisation
(i) It is a process of changing liquid sinto vapour.   
(i) It is a process of changing liquids   into vapour. 
(ii) Molecules of liquids escape from all parts of the liquids into atmosphere.
Molecules of liquids escape from upper surface of the liquid into    atmosphere.   
(iii) It is a fast process.
(iii) It is a slow process.    
(iv) It takes place only at a fixed  temperature called boiling point.
(iv) It takes place at all temperature, even at melting point.
(v) In boiling, the vapour pressure of liquids is equal to the atmospheric
(v) In evaporation the vapour pressure of liquid is less than the atmospheric  
pressure.     
pressure.     

Matter in our surrounding solved questions class9      Step-02 Read_Download