Science - Class 7

1:- What is nutrients? Write some nutrients that present in food.

Ans:- Nutrients are molecules in food that all organisms need to make energy, grow, develop, and reproduce. Nutrients are digested and then broken down into basic parts to be used by the organism.
Some nutrients are carbohydrates , proteins , fats , vitamins and minerals

 2:- How many types of nutrients? Name them.
Ans:- There are two main types of nutrients
           1-macronutrients 
           2-micronutrients.

3:- what are macronutrients ?

Ans:- nutrients that is essential in relatively large amounts to the growth and health of a living organism are called macronutrients.
There are three main categories of macronutrients  
          1-carbohydrate
          2- protein
          3- fat. 
4:- What are micronutrients?
Ans:-  nutrients that is essential in minute amounts to the growth and health of a living organism are called micronutrients.
There are two main categories of micronutrients  
          1-vitamins 
          2- minerals
          
5:- What is nutrition?
Ans:- The process of obtaining food and its utilization in the body is called nutrition.

6:- Who is the primary source of food on earth?
Ans:- Plant is the primary source of food on earth.

7:- What are autotrophs ?
Ans:- Organisms which can make their own food are called autotrophs.
            Ex- plants

8:- What are heterotrophs ?
Ans:- Organisms which can not make their own food and depend on other organisms for nutrition are called heterotrophs.
            Ex-humans , animals , birds etc.

9:-What is chlorophyll ?
Ans:- Chlorophyll is a green photosynthetic pigment that absorbs sunlight and helps plants to create their own food through photosynthesis.

9:- What are chloroplasts ?
Ans:- A chloroplast is a unique organ  to plant cells that contains chlorophyll and is responsible for enabling photosynthesis to occur so that plants can convert sunlight into chemical energy.

10:- What is photosynthesis?
Ans:- the process by which green plants use sunlight to synthesize nutrients from carbon dioxide and water with the help of chlorophyll and generates oxygen as a by-product is called photosynthesis.

We cam explain the process of photosynthesis by this word equation

Some important points about photosynthesis are
1- loss of water in the form of water vapour from stomata and general surface of plant body is called transpiration. Rate of transpiration is slow at night.
2- Photosynthesis leads to the production of sugar and starch (carbohydrates) only. Synthesis of other plant products like oils, proteins etc. may take place in the absence of sunlight and in non-green cell.
3- Consumption of carbon dioxide and release og oxygen take place in atmosphere. 
The four conditions that is necessary for the photosynthesis are
1- Presence of chlorophyll.
2- Availability of sunlight.
3- Availability of water.
4- Availability of carbon dioxide  

11:- What is stomata?
Ans:- Green leaves absorb carbondioxide from the air through pores present on their surface. these pores are called stomata.
There are large number of stomata present on the undersurface of leaves. Each stomata has two bean shaped guard cells enclosing a pore called stomatal pore. guard cells regulate the opening and closing of the stomatal pore. Inner walls of the guard cells are thicker and the outer walls are thinner. When water moves into the guard cells, they become turgid and curve away from each other leaving the pore open. on losing water , guard cells get flaccid and both come together closing stomatal pore.

12:- What are producers?
Ans:- Producers are organisms that make their own food; they are also known as autotrophs. The most common example of a producer are plants.

13:- What is transpiration?
Ans:- loss of water in the form of water vapour from stomata and general surface of plant body is called transpiration. Rate of transpiration is slow at night.

14:-Why is chlorophyll known as a miracle substance?
Ans:- Carbon dioxide cannot combine chemically with water outside the green plant to make food.  food making process is possible only with the help of chlorophyll within the green leaves. that is why chlorophyll is known as a miracle substance.

15:- What are heterotrophs ?
Ans:- Organisms which can not make their own food and obtain their food from other sources are called heterotrophs.
            Ex-non green plants , animals ,humans etc.
16:- What is heterotrophic plant?
Ans:- Plants which obtain their food from other sources are called heterotrophic plant. such mode of nutrition in plant is called heterotrophic mode of nutrition.
           Ex:- non green plants  like mushroom , insect eating plant like sundew and pitcher plant etc.

17:- How many types of heterotrophic plants depending on the source of nutrition?
Ans:- There are four types of heterotrophic plants depending on the source of nutrition
                 1- Parasites
                 2- Saprotrophs
                 3- Symbionts
                 4- insectivores

18:- What are parasitic plants?
Ans:- Those heterotrophic plants that absorb their food from other living organisms are called parasitic plants. Ex:- Cascuta , Rafflesia , Viscum.

19:-Write short notes on cuscuta.

Ans:- Cuscuta is commonly known as Dodder it is a non-green, thread-like golden

Yellow plant. It cannot synthesize its own food as it lacks chlorophyll and leaves. It obtains its nutrition from other plant on which it climbs.

Cuscuta develops special small roots, called haustoria, which penetrate into the steam and branches of the host to suck food from it. We also call cuscuta as total stem parasite because it derives its entire nutrition from the stem of the host.

20:- Write short notes on Refflesia.

Ans:- Refflesia is a parasitic plant, it is known for its largest flower in the world. This parasitic plant lacks stem, leaves and

proper roots. It has a thread-like haustorium for absorbing nutrients from the roots of host plants. It is a total root parasite as it depends entirely on roots of the host plant to obtain its nutrition.

21:- Write short notes on Viscum.

Ans:- Viscum is a rootless parasite bearing large leathery green oval leaves in pairs. It grows on the branch of the trees like mango, guava etc. Its haustorium penetrates into the stem of the host and absorbs only liquid food from it. Being a green plant, Viscum can make its own carbohydrate food with the help of its green leaves. Thus Viscum is a partial stem parasite as it is partially dependent on stem of host for its liquid nutrition.

22:- Write short notes on Saprotroph.

Ans:- Saprotroph lack chlorophyll and obtain their food from dead and decaying plant and animal bodies. Saprotrophs growing on dead and decaying plant. It may also be called saprophytes. Saprophytes include microorganisms like fungi and bacteria. Most common saprophytic fungi include mushrooms, moulds that grow on stale food such as bread and prickle, etc.

23:- Write four common moulds name.

      1- Mucor

      2- Rbizopus

      3- Penicillium

      4- Aspergills

24:- What ate saprotrophic nutrition?

Ans:- Saprophytes secrete digestive juices on dead matter to convert it into soluble from and then absorb it as their nutrition. This mode of nutrition is called saprotrophic notrition.

25:- Write short notes monotropa.

Ans:- Monotropa are saprotrophic flowering plants. These saprotrophic plants are incapable of absorbing nutrition directly from dead and decaying matter. 

Their roots associate themselves with fungal mass which assist them in absorbing soluble nutrition from dead and decaying matter.

26:- What is entamophthorales?

Ans:- Entamophthorales is a types of fungi that grows on the body of insects and also gets nutrition from their body. Entamophthorales grow and multiply themselves on the dead body of insects.

27:- What is symbionts?

Ans:- A heterotrophic mode of nutrition in which two different types of organism leave together to benifits each other such organism are called symbionts.

     Ex:- Green algae and yellowish fungus.

28:- What is symbiotic association?

Ans:- A hetrotrophic mode of nutrition which two different types of organism leave together to benifits each other such organism are called symbionts and their association is known as symbiotic association.

29:- Write an example of symbiosis and explain it.

Ans:- Lichen is an excellent  example of symbiosis. They commonly grow as white-green or bluish crust on bare rocks or bark of trees.

In this association, symbionts are green algae and yellowish fungus. Green algae contains chlorophyll and has the ability to prepare food. The fungus lacks chlorophyll and cannot prepare food, but it can absorb moisture from air. In this symbiotic association, fungus helps the green algae to survive in very harsh conditions by providing water and minerals in exchange of the carbohydrate food from it.

30:- Write short notes on rbizobium and another example of symbionants.

Ans:- The  Rbizobium bacterium in the root nodules of pea and other legiminous plant is another good example of symbionts. Rbizobium fixes atmospheric nitrogen into

usable form of nitrogen and supplies nitrogenous nutrition to the roots of leguminous plants in exchange for water and carbohydrate food. It also enriches soil with nitrogenous minerals.

31:- What are carnivorous plants? Write example.

Ans:- Those plants who trap insects and disest them for nitrogeneous nutrients are called carnivorous plant grow in soil that does not have nitrogeneous nutrition. Carnivorous plants have chlorophyll therefor they are able to make their own food. They only trap the insects for nitrogeneous nutrition. 

        Ex:- Pitcher plant, Sundew, Venusfly 

                trap and Bladder wort.

32:- Write short notes on pitcher plant.

Ans:- The tip of green leaf of pitcher plant is modified into a tubular pitcher-like structure with a laid. The bottom of the pitcher has sweet digestive juice which attracts insects to get into the pitcher. From inside, the pitcher is lined with downward pointing hair which do not allow the visiting insect to escape. The insect slips down and gets drowned in the juice where it gets killed and the nutrients from the insect bodies are absorbed into the leaf.

33:- Write short notes on sundew.

Ans:- Leaves of sundew are covered with numerous sensative glandular hair which glitter in the sun as dew-drops, hence the plant has its name. Insect which comes in contact with these hair gets entanled, killed and the nutrients are abdorbed into the leaves.

34:- Write short notes on Venus flytrap.

Ans:- Leaves in Venus flytrap are green with extend flat petiole. The petiole bears a leaf blade that is devided into a pair of terminals lobes hinged at the midrib. The upper surface of the lobes contain a red pigment and stiff sensitive glandular hairs. As soon as an insect comes in contact with the hair on the leaf, the two lobes of the leaf get closed. It kills and digests the insect, and absorbs nutrients from its body.

35:- Write short notes on Bladderwort.

Ans:- Bladderwort is an aquatic plant. The leaves of the plant are modified into small bladders with trap-door entrance. These bladder allow entry but not the exit of the insect. An insect coming near the mouth of the bladder is suckef into it. The insect is killed and digested.

36:- How is soil enriched with nutrition?

Ans:- Soil is enriched with nutrition by three ways.

   1- By adding fertilizers like urea, potash,          phosphate etc. to increase nutrients            and minerals to the soil.

   2- By adding mannure like cow dung.

   3- By dead and decaying leaves and.               animals.

 
Utilization of Food in plants and Animal, Chapter-2, Class-7, Sub- science. 


1:- Why do living organism utilize food?

Ans:- Living organisms utlized food for growth and obtain energy to perform various life activities.

2:-Who are autotrophs?

Ans:- Plants are autotrophs because they prepare their own food

3:- By which process plants prepare their food?

Ans:- Photosynthesis

4:- What is the first product of photosynthesis?

Ans:-The first product of photosynthesis is Sugar, which is in the form of glucose.

5:- What is the function of starch?

Ans:- Starch is the first stored food in leaf and it is translocated, from the leaves, to different parts of the plant body during night. Starch formed during the day is reconverted to soluble sugar when it is dark. This soluble sugar moves through veins in leaves and phloem tubes in stem to reach different parts of the plant body.

6:- How proteins, oils, and other food products formed in plant?

Ans:- Sugar and starch combine with other materials to form proteins, oils, and other food products in different parts of the plant body.

7:- How do plants utilize their prepare food?

Ans:- In plants, the food is utilized in the following four ways:-

 1- GROWTH:- Food from the leaves is translocated to the roots, stem, fruits and seed. Which help the plant to grow in height and in formation of new branches, new leaves, flowers, fruits and seeds.

 2- STORAGE:- In plants, food may be stored in modified roots in modified stem in leaves and in fruits and seeds.

3:- REPRODUCTION:- Food is utilized for the formation of seeds.

4:- ENERGY:- Food is also utilized by plants

for releasing energy during the process of respiration during respiration, oxygen present in cell combines with food and formed carbon dioxide and water with the release of energy.

8:- Write three difference of photosynthesis and respiration in a plant.

Ans:- The three differences between photosynthesis and respiration in a plant are.

 1- Photosynthesis occurs during the day.          but respiration occurs at night.

 2- Photosynthesis is many time faster              than the process of respiration in plant.

 3- Sugar is formed during photosynthesis        but sugar is consumed during.                      respiration.

9:- How many types of mode of nutrition in

living organism.

Ans:- There are two types of mode of nutrition in living organism.

 1- Autotrophic nutrition

 2- Heterotrophic nutrition

10:- How many types of animals depending upon the kind of food and the way they take their food?

Ans:- There are four types of animals dep-ending upon the kind of food and the way they take their food.

 1-Holozoic

 2- Saprotrophs

 3- Parasites

 4- Scavengers

11:- What are holozoic animals?

Ans:- Those animals that take food into the mouth and chewing or gulping are called holozoic animals.

    Ex:- Rabbits, Lion, Crows, Snakes etc.

12:- How many types of holozoic animals?

Ans:- There are there types of holozoic animals.

  1- Herbivores

  2- Carnivores

  3- Omnivores

13:- What is herbivores?

Ans:- Those animals that eat only plant and product is called herbivores.

   Ex:- Cow, Elephants etc.

14:- What is carnivores?

Ans:- Those animals that eat only flesh of other animals is called carnivores.

    Ex:- Lion, Fax etc.

15:- What is omnivores?

Ans:- Those animals that eat both flesh and plant product is called omnivores.

     Ex:- Crow, Dog etc.

16:- How many stages involved in holozoic

nutrition? Explain.

Ans:- There are five stages involved in holozoic nutrition.

 1- Ingestion:- The intake of food into the body is called ingestion. Different animals use different methods to ingest food. Like a frog uses its stickly tongue to capture a flying insect. Snakes and alligators gulp the prey whole.

2- Digestion:- This stage involves  in  breakdown of complex and insoluble food particles into smaller soluble substances by the chemical action of different enzymes and digestive juice.

3-Absorption:- In this stage, the simple substances are absorbed and taken into the blood.

4- Assimilation:- In this stage, blood carries the absorbed food to body cells where they are utilized for energy, growth and helps in performing diffrent life functions.

5- Egestion:- This stage involves the removal of undigested food from the body.

17:- What is saprotrophs?

Ans:- Animals that drive their nutrition from dead and decaying organic matter are called saprotrophs.

    Ex:- earthworm and maggots.

18:- what is parasites? 

Ans:- Parasites animals feed on the body of a living host. They do not give anything to the host in return. Parasites are invariably smaller than their hosts and they secure shelter protection and nutrition from the host.

19:- How many types of parasites?

Ans:- There are two types of parasites.

 1- Ectoparasites

 2- Endoparasotes

20:- What is ectoparasites?

Ans:- These parasites live on the body of host suck their blood. 

    Ex:- lice and bedbugs.

21:- What is endoparasites?

Ans:- Endoparasites live within the body of the host. For example Ascaris, hookworm and tapeworm are some common parasites. They enter the host's body through the food canal and obtain nutrition from there host.  another endoparasites are liver fluck and plasmodium. liver fluke obtain nutrition from the liver tissue of the host. Plasmodium lives in the salivary glands of female Anopheles mosquito. Which causes malaria.

22:- What is Amoeba?

Ans:-Amoeba is a single-celled organism that perform all its life activities within its unicellular body. Amoeba has no fixed shape. It is mass of gel-like living substance with a nucleus. Nucleus is surrounded by the living substance, called cytoplasm. The cytoplasm has water and food filled cavities or vacuoles.  It is surrounded by a thin cell wall. 

23:- How does amoeba get its nutrition?

Ans:- Amoeba feeds on microorganism like  algae, bacterial cells and spores of plants found in water. When a food particle comes in contact with the body of Amoeba, it gives out finger-like projections, called pseudopodia. The pseudopodia completely surround the food particle forming a cavity, called food vacuoles. The food is thus engulfed and taken into the cell cytoplasm. This process of engulfing  the food by Amoeba is called enfocytosis. Once the food is ingested, some digestive juice are secreted into the food vacuole that result in digestion and assimilation of food within the cell. The absorbed food is then utlized for growth, multiplication and other life activities of the amoeba. After assimilation of the food,  the undigested food is eliminated out of the body through an opening which appears on side of the vacuole. This process is called ingestion. D

24:- How food is digested and utilized in human body? Explain. 

Ans:- The digestion and utilization in human beings are completed in five steps.

It being from ingestion and ends by emotion. 

 1-Ingestion:- Ingestion is the process by.         which food is taken in by an organism.       Humans ingest food by the mouth.

 2- Digestion:- The process of digestion         begins from mouth and is completed 

through a set of organs that constitutes the digestive system. The vital organs involved in the human digestive system are mouth, oesophagus, stomach, small Intestine, large intestine, rectum and anus

3- Absorption:- Once the food is digested and converted into solution form, The nutrients of the soluble food is absorbed by the walls of the small intestine and goes into the blood.  The walls of intestine have millions of tiny projections, called villi. These villies help the small intestine in absorption.            

4- Assimilation:- The nutrition reaching each cell of the body through blood are used for energy, growth and repair of the body, this is the last stage of digestion and is called assimilation of food. 

5- Egestion:- Rectum, the last part of large intestine, receives the semi-solid, undigested food. It keeps the waste food till it is passed out as faces from the body through anus. This is called egestion. 

25:- What is saliva? 

Ans:- Saliva is the salivary juice  secreted into the mouth from the salivary glands. It is an alkaline digestive juice with mucus that partily converts starch into sugar. Saliva also makes the food soft and slippery so that it can be easily swallowed.

26:- What is tongue? 

Ans:- Tongue is a muscular structure attached at the back to the floor of vuccal cavity. It helps to taste the food. It also turns and mixes food with saliva and pushes it towards teeth in the mouth. 

27:- What is mastication? 

Ans:- The process of chewing and mixing the food with saliva in mouth is called mastication. 

28:- What is the hardest part of the human body?

Ans:- The teeth are the hardest part of human body. 

29:- How many types of teeth?

Ans:- There are two types of teeth.

          1- Milk teeth

          2- Permanent teeth 

30:- Write short notes on milk teeth. 

Ans:- A child has set of twenty teeth these are called milk teeth. 

31:- Write short notes on permanent teeth.

Ans:- After the age of ten years milk teeth are lost and replaced by permanent teeth. Permanent teeth has set of 32 teeth. 

32:- How many types of permanent teeth?

Ans:- There are four types of permanent teeth.

  1- Incisor

  2- Canines

  3- Premolaras

  4- Molars

33:- Write short notes on incisor. 

Ans:- There are 4 incisors in front on each jaw. Incisors are chisel-shaped and help in biting and cutting. It is also called cutting teeth. There are eight incisors in human mouth.

34:- Write short notes on canines? 

Ans:- There are 2canines in each jaw one on each side of the incisors. They are pointed and help in tearing the food. So it is also called tearing teeth. There are four canines in human mouth. 

35:- Write short notes on premolars. 

Ans:- There are four premolars on each jaw, two on each side of the canines. They are broad with almost flat surface. They help in crushing and chewing the food. They are also called chewing teeth. There are eight premolars in human mouth. 

36:- Write short notes on molars. 

Ans:- There are 6 molars on each jaw,  three on each side of the premolars. They help in fine grinding the food. So they are also called grinding teeth. There are twelve molars in our mouth. 

37:- Write short notes on oesophagus. 

Ans:- Oesophagus is also known as food pipe. No digestive juice is added to food in the oesophagus. Therefor no any changes happen in food in oesophagus.

     The movement of food in oesophagus is unidirectional.

38:- Write short notes on stomach.

Ans:- Stomach is a thick-walled, J-shaped muscular bag. It is placed slightly towards the left side of the abdomen. The gastric glands located in the wall of stomach secrete gastric juice and hydrochloric acid into it. The food received in the stomach through the food pipe gets mixed with gastric juice and hydrochloric acid and is churned for about two to three hours. 

Hydrochloric acid turns the alkaline base of the food into acidic base and kills of  the germs present in it. Pepsin, an enzyme, present in gastric juice converts complex protein food into simpler substances called peptides. This, food in the stomach turns into an acidic milky paste called chyme. 

39:- Write short notes on liver.

Ans:- Liver is the largest glands of human body. It secretes a digestive juice called bile.  Bile gets collected into the bladder which is connected to the liver on side and small intestine on the other side. Gall bladder collects bile from the  liver and release in into the small intestine from time to time. Bile when mixes with the chyme, breaks down fast and oils into fine fat and oil droplets.  These droplets of fat and oil mixed with water to form emulsion. This process is called emulsification of fat. 

40:- Write short notes on pancreas. 

Ans:- Pancreas is a large, elongated gland lying between the folds of stomach and small intestine. It secretes pancreatic juice into small intestine which converts acidic chyme into alkaline base. The pancreatic juice includes three enzymes-amylase, retrain and lipase. Amylase acts on starch to converts it into sugars lipase converts emulsified fat into fatty acids and glycerol and retrain acts on proteins them into amino acids. It is interesting to note that liver and pancreas are not part of the alimentary canal, but these organs are linked with the secretion of digestive juices.

41:- Write short notes on small intestine.

Ans:- Small intestine is a long coiled tube attached to the stomach. Small intestine is the longest part of the food canal. The digestion of food is completed in the small intestine. Also, the walls of intestine secrete intestinal juice which is a combination of three digestive juices. It converts all the components of food into simpler soluble form. 

42:- Write short notes on large intestine.

Ans:- Large intestine is broader but shorter

in length than small intestine. The digestion of  food completes in the small intestine leaving behind the behind the waste or undigested food. This waste food is passed from the small intestine into the large intestine where its wall absorbs remaining water,  minerals, and vitamins from it and semi-solid lumps are left behind. This semi-solid waste is pushed into the rectum. 

43:- What are ruminants? 

Ans:- Those animals which have normally four chambered. Stomach to digest their food. They sallow food and then bring it back again from the second chamber of the stomach to continue chewing it. Such animals are called ruminants. 

     Ex:- Cow, Goat,  Buffalo etc. 

44:- Write some characteristics of ruminants.

Ans:- Some characteristics of ruminants are. 

  1- They are grass eating animals.

  2- They digest their food in two stages. 

  3- They have a pair of hoofs in each leg. 

  4- They change cellulose into.                             carbohydrates while digestion.

45:- What is rumination? 

Ans:- The process of allowing the food and than bringing it back in the mouth to chew it again is called rumination.

46:- How does ingestion of food happen in ruminants?

Ans:- Ingestion of food happen in ruminants by the tongue they use their tongue to grasp a clamp of grass. 

47:- Write the structure and function of teeth of cow. 

Ans:- Cows have well-developed incisors on their lower jaw to cut the food into pieces. Canines are absent on both the upper and lower jaw. At the back of mouth, strong premolars and molars are present on both sides of the upper and lower jaw. 

While gazing, cow cuts grass with the incisors only on its lower jaw. The molars shred the grass  into smaller pieces. 

48:- Explain the digestion of food in cow. 

Ans:- The digestive tract of  cow consists of mouth,  oesophagus, four-chambred muscular stomach, small intestine and large intestine. The four chambers of the stomach are: ramen, reticulum, possum and abomasum. The cow holds the grass in the mouth for short time and then start chewing till it is broken down into small pieces. These small pieces get mix with the saliva and swallow quickly into the first stomach,  the ramen. 

RUMEN:- It is the largest compartment out of  the four chambers of stomach. The ramen serves as the storage place. Ramen generate microbials that helps in the digestion of some part of the food that is cellulose.

RETICULUM:- Reticulum resembles a honeycomb which plays a role particle separation from food. The partially digested food is passed on from the ramen to the second chamber of the stomach, the reticulum. In reticulum, further bacteria fermentation of food takes place and results in the formation of partially digested soft chunks of food called the cud. While resting, the cud is brought back from the reticulum to the mouth where it is chewed throughly and is mixed with more of saliva.

OMASUM:- It is a globe-shaped structure. It contains folds of tissue just like the pages in a book. Here,  the excess of water is absorbed from the pulp and this is passed into the fourth chamber of the stomach, the animation. 

ABOMASUM:- It is also known as true stomach. It is the only compartment that has glandular lining on its walls. These glandular walls give out hydrochloric acid and digestive enzymes, needed for further breakdown of the food. The food is then passed into the small intestine for complete digestion and absorption of the nutrients. 

Fibre to Fabric,  ch-3, class-7, science

1:- What are natural fibres? Give example.

Ans:- The fibres obtained from plants and animals are called natural fibres.

  Ex:- Cotton, jute, flax,  wool and silk etc

2:- What are synthetic fibres? Give example.

Ans:- The fibres that are synthesized from chemicals and are made by man are called man-made or synthetic fibres.

  Ex:- Rayon and polyester. 

3:- Write short notes on production and processing.

Ans:- The wool fibres is natural hair that grow on the body of an animal. It is called fleece. The fleece is composed of protein substance called keratin. Chemically, the protein keratin is composed of carbon, hydrogen, nitrogen and sulphur. The spongy feel of the wool fibres is due to the presence of crimps or curls in it. Wool fibre is scaly on its surface. 

     Basically, there are two kinds of hair of fleece. 

1- Kemp- The Kemp is the coarse fibre which is slightly thick, straight and rough.

2- Soft under Hair-The soft under hair with crimps are fine and soft. Wool is obtained from the fleece that contains only fine, soft and curly under hair. 

4.write three factors on which quality of fibre depend.

And-The three factors on which quality of fibre depend.

1-The age and health condition of animal. 

2- The environment in which the animals have been living.

3- The part of the body of animals from which wool is being sheared. Wool from the shoulder region and the under belly of sheep is better. 

5:- How many types of wool? Name them and define it. 

Ans:- There are eight types of wool. 

 1- Lamb's wool- It comes from the baby sheep. It is considered to be of superior quality.

2- Soft wool- It comes from a adult and healthy sheep. 

3- Rough wool- It comes from aged and diseased sheep, camel and yak. 

4- Angora wool- It comes from Angora rabbit. Angora wool is too soft and fluffy.

5- Mohair- It comes from Angora goat. This wool is long and smooth.

6- Merino- It comes from a special breed of sheep from Spain and now reared in Australia. This wool is exceptionally soft, fluffy and light in weight. 

7- Pashmina wool- It comes from hill goats living in cold regions. It is soft and silky wool. It is valued for its soft texture. 

8- Shatoosh- It the softest and costliest wool. It comes from the fleece of Tibetan Antelope churi.

6:- Write five name of fleece giving animal. 

Ans:- Sheep, Angora goat, Angora rabbit, Alpaca, Yak. 

7:- Write short notes on eating habits of fleece giving animal.

Ans:- Fleece giving animal like sheep lambs graze on grass and leaves. They are also feed on seeds, grains and oil cake since these proteins reach food provide nutrition for better growth of fleece.

8:- How can we process the fleece? Describe it. 

Ans:- Fleece are processed in six steps- 

  1- Sharing

  2- Washing or Sourcing

  3- Grading or sorting 

  4- Carding or combing

5-spining

6-dyeing

1-sharing= sharing is the process of removal of the fleece from the skin of sheep. Fleece is generally sheared once year in the spring season. 

2-washing or scouring =the fleece is washed to remove dirt,dried perspiration and the yolk. This is called washing or scouring. 

3-grading or sorting= After scouring the fleece is sorted and graded by hand into separate piles of singular nature. This is called grading. Grading is a essential because variety of wool defers with the different breeds of sheep. Also, the fleece obtained from the different parts of the same sheep differs in length,softness and structure. 

4-carding or combing=The fibres after sorting are untangled.They are passed through the rollers covered with fine sheet of cloth having thin wire teeth. These rollers carding the fibres  easily. 

5-spinning =The narrow fibres are passed through spinning machines where the fibres are twisted and made into yarn. This is called spinning. 

6-Dyeing= At least creamy wool yarn is dyed in different  colors  as desired.

9- What is weaving? 

Ans-During weaving, the two sets of yarn are used of which one yarn is arranged length wise. It is called warp, and another is arranged cross wise, called weft. Weft is set through a spindal on a shuttle. The warp and weft or interlaced. 

10:- What is knitting?

Ans:- Knitting wool involves the use of single yarn. Pullovers, vests and socks are knitted from knitting wool on a machine or using a pair of needle making loops. Knitted wears are loose, stretchable and comfortable to wear. 

11:- Write a occupational hazard of wool industry.

Ans:- Most cattle suffer from anthrax disease and carry causative bacteria of the disease. People working in the wool sorting department are at high risk of aquiring the anthrax infection through cuts or any open wound on their body, especially on hands. Bacteria enter the blood through the cut and cause blisters on the skin and fatal blood disease called, the  sitter's disease. 

12:- Write short notes on Silk. 

Ans:- Silk is a fine, strong and lustrous natural fibre. It is made of proteins- fibroid and sericin.Silk fibre is produced by the caterpillar that is an insect of the silk moth. The scientific name of silk moth is Bombyx mori. It produces silk in form of silk filaments. 

13:- Write five quality of silk. 

Ans:- The five quality of silk are. 

 1- Silk is a strong natural fibre. 

 2- It is lustrous, soft and all weather.               fabric. 

 3- It is a little hygroscopic and does not.         wrinkle easily. 

 4- Silk garments keep the bady of wearer.       warm. 

 5- Silk fabric smoulders over the flame.           giving out the smell of a burning hair,            leaving behind black lump. 

 

14:- Write four uses of Silk. 

Ans:- The four uses of silk are. 

1- Silk is widely used for making ribbons,        scarves, saris, shirt, neckties, silk                carpets, upholstery and other garments. 

2- Silk thread is used to stick sutures after       surgery. 

3- In industry, silk is used for making                parachute, fishing fibres and nets,                insulation coils and rubber tyres. 

4- It is used in knitting broader on clothes.

15:- Write a short notes on the history of silk. 

Ans:- The original home of the silkworms moth is China. Chinese developed silk some 6000 years back. In early days, Chinese silk was known as a wonderful fabric throughout the world. Discovery of silk has a legend in support of its origin in China. Once, Chinese Emperor, Huang- Ti while walking with his Empress, Hsi-Ling She, in his mulberry orchard observed damaged leaves on mulberry trees. Empress got curious to learn about the reason for the damage to the leaves. She found worms crawling and eating into the leaves on mulberry trees. Some of the worms had surrounded themselves with a pale ball-like structure (the cocoon) which were hanging attached to the twigs on the trees, along with the damaged leaves and the worms. While she was observing the damaged mulberry leaves, with a cup of hot tea in her hand a cocoon fell into her tea. As luck would have it, the delicate fibres from the cocoon in her tea got separated and were seen floating on tea. It was this chance experience that made Empress learn to reel the silk filaments from cocoons and this lead to the discovery of silk. This was the beginning of silk industry in China. Silk became extremely popular and a product of envy throughout the world around China. 

    China kept the process of making silk a secret for many years till in and around 600 A.D. some Monks, who had gone to China managed to smuggle two mulberry saplings and some silkworms under their tunics. These were then cultivated in a country outdide China. From then, silk is  being produced in the West also. 

16:- Write short notes on the Life cycle of a silk moth.

Ans:- The life cycle of silk moth is completed in four stages-

1- Eggs- A female moth lays nearly 500 eggs on green mulberry leaves. The eggs remain glued to the leaf with a sticky substance surroundings them.

2- Larvae- In a few days, the eggs hatch into larvae or caterpillars. The larvae feed themselves voraciously on fresh mulberry leaves, day and night, for 15 to 30 days. By that time, they grow into big caterpillars, called the silkworms. Each silkworm bears two silk-glands along the sides of the head of its body. 

3- Cocoon with pupa within- The grown up silkworm stops eating and stars exuding liquid silk in the air from the glands on its head by swinging it's head all round its body. The exuded silk-liquid soon dries up and forms a fine and strong covering of silk filaments around its body. This covering of silk-filaments in which the caterpillar sleeps is called the cocoon. The cocoon with the silkworm inside is called the pupa stage. 

4- Adult winged moth- The pupa inside the cocoon develops into a moth with antennae and wings. The moth forces its way out of cocoon by cutting through the filament of silk. 

17:- What is sericulture?

Ans:- The bearing and rearing of silkworm for producing improved quality of risk is called sericulture. It is also called silk farming. 

18:- Which state of India is the biggest producer of superior quality of silk?

Ans:- Karnatka state in India is the biggest producer of superior quality of silk.

19:- Where is the sericulture research center?

Ans:- Mysore 

20:- Where is the regional sericulture research center?

Ans:- Coonoor

21:- Write five good quantity of silk that is produced in India. 

Ans:- Mysore, Kanjiwaram, Tassar, Mooga and Kosa

22:- Who is the second largest producer of silk? 

Ans:- India

23:- How can silk produced?  write in steps. 

Ans:- The process of silk production involves following steps. 

Steps 1- Selection of  healthiest moths for breeding. Each adult female moth lays nearly 500 eggs. 

Steps 2- The eggs are hatched and larvae come out. Larvae feed mulberry leaves voraciously, day and night, for about a month and grow into caterpillars.

Steps 3- These grown up silkworms stop eating and start spinning cocoons around themselves. The cocoon is made from a continuous filament of silk which is 900m to 1000m in length.

Steps 4- The fully grown cocoons enclosing pupae are collected and immersed in hot water and then in cold water bath. These loosens the silk fibres to separate out. The cocoons are then dried under the sun or in driers. 

Steps 5- The loosen, dried silk filaments are unwound from the cocoon. The process of unwinding the filaments from cocoons is called reeling the filaments.

Steps 6- Silk threads coming out on reeling are clean and smooth hence they can be directly spun into long yarn in spinning mills. The skill thread may also be dyed with desired colours and spun into silk fabric.

24:- Write two health problems associated with sericulture.

Ans:- 1- One placing cocoons in boiling water, pupae lying inside the cocoon are killed. The inhalation of vapour may cause respiratory problems like asthma, bronchitis, etc. 

2- Workers transferring cocoons from hot water to cold water will result in blistered skin or may cause peeling of the skin of hands and feet. 

 

Heat and temperature, chapter-4, class-7, science

1:- What is heat?
Ans:- Heat is a form of kinetic energy that provides us the sensation of hotness of a thing. heat  energy moves between two things when one of them is hotter than the other. 

2:- By how many ways heat energy travels from a region of higher temperature body to a region of lower temperature body?
Ans:- Heat energy travels from a region of higher temperature body to a region of lower temperature body in three ways:-
            1- Conduction
            2- Convection
            3- Radiation
3:- What is conduction ?
Ans:- The process of transmission of heat from one particles to another in solids, without actual movement of particles from their positions is called conduction. 

4:- Write two conditions that are responsible for the conduction of heat. 

Ans:- The two conditions that are responsible for the conduction of heat are:-

1- Heat travels from one object to another only when the two objects are in contact with one another. 

2- The temperature of the two ends of the same object or the temperature of the two objects through which heat is to travel must be different from one another. Conduction of heat stops as soon as the temperature of the entire set up reaches the same level.

5:- What are conductors? 

Ans:- Those materials which allow heat and electricity to pass through them are called conductors. 

      Ex:- Iron, copper, silver, gold, aluminium, mercury etc. 

6:- Write three uses of conductors are. 

Ans:- The three uses of conductors are :-

 1- Conductors like copper, aluminium and steel are used to make utensils. 

 2- Conductors like mercury is used in thermometer because it is a good absorber of heat. 

 3:- Conductors like copper is used to make radiators to decrease temperature. 

7:- What are non conductors? Give examples. 

Ans:- Those materials which do not allow heat and electricity to pass through them are called non-conductors. Non-conductor is also known as insulator. 

        Ex:- Wood, air, paper, plastic etc. 

8:- Write four uses of Insulator of heat. 

Ans:- The four uses of Insulator of heat are:- 

  1:- Insulators like wool and air wool and.         air protect ourselves from cold. 

  2:- Insulator like plaster of Paris is used.         to make roof which protects our.                   selves from heat. 

  4:- Insulators like Bakelite plastic or wood is used in utensils to save our hands from getting brunt. 

   5:- Insulator like oil is used in electrical.            transformers to keep them cool. 

9:- What is Convection?
Ans:- Heat convection is a mode of heat transfer in which heat moves through a gas or a liquid. In convection the hotter part of gas or liquid rises up and the cooler heavier part sink down.
  For example:- Boild water, 

10:- Write four places where convection currents used? 

Ans:- The four places where convection currents used are:-

  1:- Convection currents is used in room heater as room heater is always kept on the floor. 

  2:- Convection current is used in air conditioner as air conditioner is always installed at height. 

  3:- Convection current is used in Exhaust fan as exhaust fan is always installed at higher level. 

  4:- Convection current is used in sea breeze and land breeze. 

10:- What is Radiation?
Ans:- Heat transfer from a body with a high temperature to a body with a lower temperature when bodies are not in direct physical contect with each other is called radiation of heat.

12:- Write three factors that affect obserption of radiant. 

Ans:- The Three factors that affect the obserption of radiant energy are. 

 1- The nature of the material -

  =Metal observe more heat than non metals. 

 2- Distance from the source of heat -

 =Nearer object receives more heat than the farther object. 

 3- Colour and the surface of the object-

 =Dark colour observe more heat than light colour. 

Write three medium through which heat radiation pass? 

Ans:- Heat radiation passes through vacuum, air and transparent medium. 

Why do we feel cool under shade? 

Ans:- We feel cool under because shade because shade is a dark medium. The heat radiation Can not pass through the dark or opaque medium. 

Why is the oil tanker polished silvery light colour? 

Ans:- Oil tanker polished silvery light colour because silvery light colour reflect most of the heat radiation and keep the tanker cool. 

Why is the house painted white from out side? 

Ans:- House is painted white from out side because white paint colour reflects most of the heat radiation and keep the house cool. 

Why do we wear light coloured clothes in summer? 

Ans:- We wear light coloured clothes in summer because light coloured clothes reflect maximum heat radiation and keep us cool. 

Why is the base of cooking utensils kept dark and side of utensils kept shiny? 

Ans:- The base of cooking utensils kept dark because dark colour observe maximum heat from flame and side of utensils is kept light colour because light colour radiate minimum heat from sides and keep the contents warm for long. 

11:- What is temperature?
Ans:-Temperature is a measure of the average heat of the particles in a substance. It does not depend on the size or type of object. Temperature indicates the degree of hotness or coldness of an object.

12:- What is thermometer? 

Ans:- An instrument that is used to measure the temperature of a body is called thermometer. 

13:- What is the temperature of human body in degree Celsius? 

Ans:- 37%

14:- What is the temperature of human body in degree Fahrenheit?

Ans:- 98.4%

15:- Write short notes on the structure of thermometer.

Ans:- Thermometer is made from fine, clear, transparent, colourless glass. It has a stem and a bulb. The stem is a thick glass tube, it has a fine bore called capillary running along its full length. One end of the capillary ends in a thin walled glass bulb filled with mercury or alcohol. The other end of it is closed after removing all the air inside it. There are markings on the body of thermometer which help in reading the temperature of a body. A thermometer has a scale marked on its stem to read the temperature. All the marking on the stem of a thermometer are equidistant, and are called graduations. The length of thermometer tube from 0 to 100 is graduated in 100  equal divisions. Each unit or division on the scale is termed as degree.

16:- What is degree? 

Ans:- Degree is a unit measure of temperature. Degree is denoted by a symbol (°).

17:- What is melting point and freezing point of water?

Ans:- 0°

18:- What is the boiling point of water? 

Ans:- 100°c

19:- Write the two most commonly used scale on thermometer.

Ans:- Degree Celsius (°c) 

          Degree Fahrenheit (°f) 

20:- What is the SI unit of temperature? 

Ans:- Kelvin 

21:- Write short notes on Celsius thermometer.

Ans:- The most widely used scale to measure temperature is the Celsius scale. It is named after the Scientist, Anders Celsius from Greece. He suggested that the length of the stem of a thermometer between the 'freezing point of water into ice' and the 'boiling point of water' be grated into 100 equal parts and each graduation is denoted in short form as '°c'. Degree, the unit measure of temperature is denoted by the symbol (°). Hence the thermometer with 100 graduations (degree) between these two points is named as thermometer.

22:- What is lower standard (fixed) point? 

Ans:- 0°c is the melting point of ice and is called the lower standards (fixed) point.

23:- What is the upper standard (fixed) point? 

Ans:- 100°c is the boiling point of water and is called the upper standard (fixed) point. 

24:- What is different between centigrade and Celsius? 

Ans:- The term Centigrade is used instead of Celsius, and is also denoted by the symbol '°c'. In term centigrade, 'centi' means 1/100, and grade stands for the unit of temperature, the graduation or degree. Hence, each division on the Celsius scale represent 1°C (one degree Celsius or one degree centigrade).

   NOTES- During melting of ice, the.                         temperature of ice remains.                           constant at 0°C. 

    NOTES- The temperature of stem over.               boiling water remains constant at.               100°C. 

25:- Write short notes on Fahrenheit Scale. 

Ans:- The Fahrenheit scale was given of German scientist, 'Gabriel Fahrenheit'. He suggested that the melting point of ice (or lower fixed point) be marked as 32°F and the boiling point of water (or upper fixed point) as 212°F. Like the Celsius scale, the distance between these two points is divided and graduated into 180 equal divisions, called degree Fahrenheit (°F) and also called Fahrenheit thermometer. 

26:- Find the relation and formula of Celsius and Fahrenheit scale. 

Ans:- The intervals in Celsius scale = 100

          The interval in Fahrenheit scale= 180

          So the ratio = 100:180

                               = 100/180

                               = 5/9

                               = 5:9

  The formula which is used to convert °C.      to °F is.  F= (c*9/5)+32

  The formula which is used to convert °F.       to °C is.    C= 5/9(F-32)

27:- Write some realities between Fahrenheit and Celsius. 

Ans:- 32°F is same as 0°C. They are freezing point of water. 

    212°F is same as 100°C. They are boiling point of water. 

   -40° is same as -40°. -40°is that temperature on which Fahrenheit and Celsius become equal. 

28:- How many types of thermometer? 

Ans:- There are two types of thermometer. 

  1- Liquid thermometer 

  2- Dry thermometer 

29:- What is liquid thermometer? 

Ans:- Liquid thermometer is the one in which a liquid is used as an indicator in the capillary. It includes mercury and alcohol thermometers. Liquid thermometers make use of the property of a liquid to expand and contract uniformly for every degree change in temperature.

30:- How many types of liquid thermometers? 

Ans:- There are two types of liquid thermometers. 

  1- Mercury thermometer 

  2- Alcohol thermometer 

31:- How many types of mercury thermometer? 

Ans:- There are two types of mercury thermometer. 

   1- Clinical thermometer 

   2- Laboratory thermometer 

32:- What is clinical thermometer? 

Ans:- A thermometer that is use to measure the temperature of the body of a person is called clinical thermometer. 

33:- Write structure and function of clinical thermometer.

Ans:- The liquid used inside the clinical thermometer is mercury. Clinical thermometer is specially designed with a short and handy stem which is in triangular shape. These shapes enable to view clearly magnified mercury thread  in the capillary. These thermometers are graduated both in Celsius scale and the Fahrenheit scale. There is a kink in the capillary towards the bulb that prevents the flow of the mercury back into the bulb. This helps in getting the actual temperature of the body. It has a long bulb and a fine capillary which make the thermometer more sensitive.

34:- What is laboratory thermometer? 

Ans:- The thermometer that is used in laboratory to measure the temperature of things is called a laboratory thermometer.

35:- What do you know about Mercury? 

Ans:- Mercury looks like a sliver grey in colour. It is used to find the temperature between -10°C to 110°C. It is only a metal that is in the form of liquid.

36:- Write short notes on alcohol thermometer. 

Ans:- Red coloured alcohol is used in alcohol thermometer. This thermometer is used to measure the temperature of a room or the temperature of environment around. The temperature range of this thermometer is from -40°C to +50°C. Being cheaper and non-poisonous, alcohol is safer than mercury. 

37:- What is the disadvantage of alcohol thermometer? 

Ans:- It can only be used for measuring limited range of temperature. It cannot measure temperatures higher than 78°C. 

38:- Write six advantage of mercury thermometer. 

Ans:- The six advantages of mercury thermometer over the alcohol thermometer are:

   1:- Mercury is shiny, so it is clearly                    visible inside the thermometer. 

   2:- It takes heat quickly. 

   3:- It shows nearly uniform rate of                      expansion over a wide range of.                    temperature. 

   4:- It's freezing point is much below 0°C.  

        It freezes at approx. -39°C. 

   5:- Its boiling point is approx. 357°C.                which is much above 100°C.

   6:- It is non-sticky so does not sick to                the walls of capillary. 

39:- Write three disadvantage of Mercury thermometer. 

Ans:- The three disadvantage of mercury thermometer are. 

    1:- It is costly. 

    2:- It is poisonous.

    3:- Mercury cannot be collected back, if           spilled.

40:- Write short notes on digital thermometer. 

Ans:- Digital thermometers use an electronic device called thermistor in place of mercury. Thermostor is sensitive to heat. It is placed inside the tip of thermometer and helps to measure the temperature of body. Thermostor displays the temperature sensed by it in digitas in a liquid crystal display (LCD). These thermometers give quick and accurate results. Also they are safe and easy to handle. 

41:- Write four precautions that we should must take while measuring temperature. 

Ans:- The four precautions that should must take while measuring temperature. 

  1- Thermometer should be washed and           wiped clean before use. 

  2- Never place the thermometer in hot.            water. 

  3- Shake or jerk the thermometer to bring  down the mercury column in the stem to mark near the kind to 35°C or 96°F before use.

  4- While measuring temperature of a liquid with the help of a laboratory thermometer take care that the bulb of the thermometer is completely immersed in the liquid; thermometer should not be in contact with any object other than the liquid around it; and it should remain in vertical position, throughout the experiment .

42:- What is transmission or transfer of heat? 

Ans:- A hot body loses heat energy while the cold body gains heat energy. Heat energy always flow from a hot body to a cold body. The flow of heat is also known as transmission or transfer of heat. 

43:- What is thermoflask? 

Ans:- A thermo flask is a device used to keep hot things hot and cold things cold for long. 

44:- Write short notes on the structure of a Thermo flask. 

Ans:- Thermo flask is a double -walled glass-flask. The inner walls of  the flask are silvered so that the exterior of the flask on both sides is reflective like a mirror. The air in between the two walls of the flask is pulled out and the opening is sealed to create a vacuum. The glass flask is fixed inside a protective metal or thick plastic body with the help of a spring at the base and cork-pads on sides. The mouth of the flask is closed with a tight-fitting cork or plastic stopper made from a non-cobducting material, and this cork is placed under a cover. 

45:- Write short notes on working of a thermo flask. 

Ans:- The shiny silver surfaces of the flask prevent the transfer of heat from outside to inside or vice versa by reflecting back the radiations. The vacuum between the glass walls of flask prevents the transfer of heat by conduction and convection. Cork are plastic stopper on the mouth of the flask is a bad conductor of heat thus it does not allow loss of heat by conduction and convection. The space between the glass flask and the outer body further reduces the chances of transfer of heat in any way.

Acids , Bases and Salt chapter-5

1:- how many types of substances on the basis of their own characteristics properties?

Ans:- There are three types of substances on the basis of their own characteristics properties.
           1- Acid
           2- Base
           3- Salt 

2:- What is acid? Write example.
Ans:- An acid is a sour tasting substance that can donate a hydrogen ion (H⁺) to another substance. Acids have a pH less than 7 .
     Example- malic acid that is present in apple.
                      citric acid that is present in orange
                      oxalic acid that is present in tomato
                      tartaric acid that is present in tamarind
                      Hydrochloric acid that is present in stomach 

How many groups of acid? Name them. 

Ans:- There are two groups of acid. 

     1- Organic acid

     2- Mineral acid

What are organic acids? 

Ans:- Those acids that we get from plants and animals are called organic acid. Some common organic acids are acetic acid, Ascorbic acid, lactic acid, citric acid, italic acid, carbonic acid, tartaric acid. 

Write a use of organic acid. 

Ans:- Organic acid like ascetic acid and citric acid are used as preservatives in pickles and spices. 

What are mineral acid? Give examples. 

Ans:- Acids which are synthesizer from the minerals coming from earth are called mineral acids. 

         Ex:- Hydrochloric acid (HCI), nitric acid(HNO³) sulphuric acid (H²SO4), phosphoric acid (H³PO4) and hydrofluoric acid (HF)  

Why are mineral acids also called in organic acid. 

Ans:- Mineral acids are also called in organic acid because they have no carbon. 

Write short notes on hydrofluoric acid (HF). 

Ans:- Hydrofluoric acid (HF) is the only strong acid (liquid) in which even glass is soluble. Hence, it cannot be stored in a metal, porcelain or glass bottle. It is stored in bottles made from Teflon, a kind of non-sticking plastic. As a precaution, even teflon bottle is coasted with wax from inside before hydrofluoric acid in it. There is only one antidote to HF that is calcium gluconate gel. This gel reacts with HF to form non-toxic calcium fluoride. 

Write five uses of hydrochloric acid. 

Ans:- The five uses of hydrochloric acid are. 

1- It is used as cleaning agent for kitchen sinks and sanitary ware. 

2- It is used as a cleaning agent before welding of two pieces of the same metal or two different metals. 

3- It is used in refining common salt. 

4- It is used to make aqua regia. It is made by mixing 1 part concentrated nitric acid and 3 parts concentrated hydrochloric acid. Aqua regia is used to dissolve gold, silver and platinum metals in it. It is used in refining of precious metals. 

5- It is used in galvanizatio of different metals. 

Write three uses of Nitric acid. 

Ans:- The three uses of nitric acid are. 

1- It is used in the purification of noble metals like silver and gold. 

2- It is used in the manufacturing of fertilisers and explosives such as TNT. 

3- It is used to make aqua regia in combination with hydrochloric acid. 

Write three uses of sulphuric acid. 

Ans:- The three uses of sulphuric acid are. 

1- It is used in the manufacturing of fertilisers, dyes and paints. 

2- It is used in the petroleum refinery industry. 

3- It is used in the batteries of automobiles such as trucks, cars, inverter and autos. 

Write a use of hydrofluoric acid. 

Ans:- The use of hydrofluoric acid is.

It is used for developing geometrical and floral patterns on glass by etching. 

3:- What is Base? Write example.
Ans:- A slippery substance that release hydroxide (OH⁻) ions when react with aqueous solution is called base . Bases are bitter in taste. Bases have a pH value higher than 7
      Example- Baking soda , Washing soda , lime

4:- What is Salt? Write example.
Ans:- substance that is produced by the reaction of an acid with a base is called salt.Salts have a pH value equal to 7 .
      Example- sodium chloride (common salt) 

5:- What are indicators? 

Ans:- Indicators are substances that are used to test whether a substance is acidic or basic to neutral in nature. 

   Ex:- Turmeric gives brownish red colour in basic medium and yellow colour in acidic medium. 

6:- What is litmus? 

Ans:- Litmus is the most common indicator that is used in laboratories for testing the acidic or basic nature of a solution. 

7:- How many types of litmus paper? 

Ans:- There are two types of litmus paper. 

    1- Red litmus paper 

    2- Blue litmus paper 

8:- What happens when Red litmus paper react with acid? 

Ans:- When red litmus paper reacts with acid, it shows no change. 

9:- What happens when red litmus paper react with base? 

Ans:- When red litmus paper reacts with base, it turns into blue colour. 

10:- What happens when blue litmus paper reacts with acid? 

Ans:- When blue litmus paper reacts with acid, it turns into red. 

11:- What happens when blue litmus paper reacts with base? 

Ans:- When blue litmus paper reacts with base it shows no change.  

15:- How can we prepare phenolphthalein indicator? 

Ans:- We can prepare phenolphthalein indicator by mixing phenolphthalein with alcohol.