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## 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.

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## 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.

(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.

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.

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.

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.

 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.

## Thursday, April 9, 2015

### Class7 Nutrition in Animals Science

Nutrition in animals  Holozoic nutrition:
It is a method of nutrition that involves the ingestion of liquid or solid organic material.

It involves different steps namely, ingestion, digestion, absorption, assimilation and egestion.

Human beings exhibit holozoic mode of nutrition involving five basic steps.
Digestion:
Digestion is the process by which complex food is broken down into simple absorbable form.

Digestion of food starts from mouth and ends in small intestine

Digestive system is made up of alimentary canal and associated glands.

Digestive system in human beings:
Digestive system in human beings is formed by alimentary canal and digestive glands.

Parts of alimentary canal:
It comprises different parts like mouth, oesophagus, stomach, small intestine and large intestine. It starts with mouth and ends with anus.

ingestion
The process of taking in food through mouth is called as ingestion.

Mastication

Teeth help in the process of mastication. Mastication is the process of mixing chewed food with saliva.

Digestion of food starts in the mouth with the help of salivary amylase present in the saliva.

Salivary amylase is the enzyme which digests starch into glucose for absorption

Epiglottis

Pharynx is the common channel for food and air. When we swallow food, a flap-like valve called the epiglottis closes the windpipe. Epiglottis prevents the entry of food particles into respiratory tract.

Oesophagus
Oesophagus also called as food pipe helps in conveying the food from buccal cavity to stomach. The oesophagus is also known as the gullet. It is about 25 centimetres long.

Peristaltic movements
Peristaltic movements are the alternate contractions and relaxations of oesophageal wall which bring about movement of food from buccal cavity to the stomach.

Food conveyed to the stomach is called as bolus as it is round in shape.

Stomach
Stomach is the widest part of the alimentary canal. It is a J-shaped muscular organ divided into three parts namely, cardia, fundus and pylorus regions.

Stomach as a whole can hold at about two litres of food.

Stomach secretes a fluid called as digestive juice called gastric juice .

Gastric juice
It is made up of hydrochloric acid, mucous and enzymes like pepsin and rennin.
Hydrochloric acid kills the bacteria present in the food and softens the molecules of food.

Mucous

Mucous protects inner lining of the stomach from the action of hydrochloric acid.

chyme

Digestive enzymes partially digest some nutrients like proteins and fats. Stomach churns the food into a milky paste. This partially digested food is called as chyme.

Chyme is conveyed to small intestine for further digestion. Chyme is acidic in nature.

Small intestine
Small intestine is made up of three regions namely duodenum, jejunum and ileum.

• Acidic chyme from the stomach is received by the duodenum for further digestion.
• Duodenum also receives bile form the liver. Bile reduces the acidity of chyme.
• Bile also provides alkaline environment to activate some enzymes which bring about digestion of certain nutrients in the food.
• Duodenum also receives pancreatic secretions which help in the digestion of food.
• Duodenum also secretes some enzymes on its own.
• All these substances bring about digestion of food in the intestine.
• The inner walls of small intestine are thrown into many folds which have millions of small finger like projections called villi.
Villi increase

• Villi increase the surface area for digestion as well as absorption of digested food by eight times.

Small intestine also helps in the process of absorption and assimilation.

Large intestine
• Undigested food is sent into large intestine.

Large intestine comprises of colon and rectum. Large intestine receives undigested food from small intestine.

Water from the food is reabsorbed to a great extent in the large intestine.
Semi-solid undigested waste is stored in the rectum for defecation.
Anus is the opening of the alimentary canal to the exterior. This helps in the elimination of faeces by the process of egestion.

Digestive glands:

These glands are also called as associated glands. These are also considered to be exocrine glands which have ducts to drop their secretions into the target organ directly. The secretions of the digestive glands help in the process of digestion. These glands include salivary glands, gastric glands, intestinal glands, liver and pancreas.

Salivary glands are present inside the buccal cavity. They secrete saliva. Saliva helps in lubrication of food . This saliva plays an important role in breaking down complex components like starch into simple sugars. It brings about partial digestion of starch.

Gastric glands are microscopic glandular cells present in the inner lining of the stomach. Gastric glands secrete gastric juice comprising HCl, pepsin and prorennin.

Gastric juice helps in the digestion of proteins. Gastric juice helps in emulsification of fats.

Intestinal glands are present in the inner lining of small intestine. These secrete various enzymes which aid in the process of digestion of all the components of food.

Liver is the largest gland in our body. The liver secretes a yellowish green watery fluid called bile. It is temporarily stored in a sac called the gall bladder.

Bile provides an alkaline environment for many enzymes to get active. It also reduces the acidity of chyme. Bile plays an important role in the digestion of fats.

Bile is sent into duodenum through a narrow tube-like structure called the bile duct.

Bile breaks the larger fat molecules into tiny droplets, thereby increasing their surface area, which helps in the digestion of fats easily.

Pancreas is the mixed gland. It acts as both endocrine and exocrine gland. The pancreas secretes the pancreatic juice that helps to digest carbohydrates, proteins and fats. The pancreatic juice converts carbohydrates into simple sugars and glucose, proteins into amino acids, and the lipids into fatty acids and glycerol.

Absorption: The process of allowing simple absorbable nutrients into blood capillaries through surface of the villi is called as absorption. Inner wall of small intestine comprises many finger like projections called as villi. Villi increase the surface area for absorption of food.

Each villus is made up of central structure called as lacteal which mainly absorbs simple fats and transports them into lymphatic system.

Lacteal is surrounded by a network of fine blood capillaries. Blood capillaries absorb glucose molecules and amino acids and transport them in the blood. Vitamins and minerals get readily absorbed into the blood.

Assimilation:

The process of utilisation of absorbed food, such as glucose, amino acids, fatty acids and glycerol is called as assimilation. Energy needed for various activities is obtained from glucose.

Glucose is broken in the cells in the presence of oxygen to syntheise energy in the form of ATP.

Amino acids are used for building and repairing body parts. Fatty acids and glycerol are stored in the adipose tissue and under the skin for future use.

Egestion:

It is the process by which undigested food is passed to exterior through an opening called as anus. Rectum stores undigested waste in the form of faeces. Faeces are sent out through anus.

Solved questions Class 7 Science Nutrition in Animals

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## Sunday, April 5, 2015

### Wind, storms and cyclones class 7 solved Quesion

Wind Storm and Cyclone :Natural Phenomena: 7th class Hots Questions
Question: 1. Why are people advised not to stand near fast moving train?
Ans: When train moves with high speed it creates region of lower pressure . This low pressure push man towards the train

Question: 2. Why are holes made in huge hoardings? Explain their usefulness.

Ans: Holes are made in huge hoardings to reduce air pressurecausing it to flutter or blown away.

Question: 3. in winter regions near, why does wind blow from land to sea?
Ans:. In winter the sea become warmer quickly than the land. So In winter monsoon blows from land to sea

Question: 4. Why are things colorful in appearance?

Ans: The colour of object is colour that is reflected. Thus different coulor makes things colourfull.

Question: 5. Fill the missing word in the blank spaces in the following statements:

(a) Wind is moving air.
(b) Winds are generated due to uneven heating on the earth.
(c) Near the earth’s surface warm air rises up whereas cold air comes down.
(d) Air moves from a region of high pressure to a region of low pressure.

Question: 6. Suggest two methods to find out wind direction at a given place.

Answer: Two methods to find out wind direction at a given place are:

(a) An instrument called anemometer can be used to find the direction and speed of the wind.

(b)  Hold a strip of paper outside. The direction in which the paper is blowing is the direction of the flow of  the wind.

Question: 7. State two experiences that made you think that air exerts pressure.
Answer: Two experiences that made us think that air exerts pressure are:

(a) . Whiling cycling against the direction of the wind, it is difficult to ride. It shows that the air exerts pressure.

(b) While rowing a sailboat in the direction of the wind, it is always easier to row and while rowing a sailboat  against the direction of the wind, it is very difficult to row. It also shows that the air exerts pressure.

Question: 8. You want to buy a house. Would you like to buy a house having windows but no ventilators?   Explain your answer.

Answer: No, I would not like to buy a house having windows but no ventilators. Warm air rises up and  cool air comes downward. So, to make a stream of cool and fresh air to continuously flow to the house through the windows, there must be some ventilators in the upper part of the wall.

Question: 9. Explain why holes are made in hanging banners and hoarders.

Answer: Holes are made in hanging banners and hoarders to allow air to pass through them as a result of  which there will be less pressure of air on the banners or hoarders. Unless it is done, these may be uprooted  or distorted due to the pressure of the air.

(a) I will help my neighbours in case cyclone approaches my village/town by the following ways.

(b) I will help my neighbours in shifting their household articles, domestic animals etc to a safe place.

(c) I will provide phone numbers of all emergency services like police, fie brigade and medical centers.

(d) I will give them safety advice like avoiding driving on roads through standing water, not touching wet  switches etc.   See full post

7th Wind Storm and Cyclone Living science question answer Download File

Wind, storms and cyclones class 7 solved Quesion                   Download File