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NCERT Exemplar for Class 7 – Problems and Solutions

Science for Class 7

Chapter 1: Nutrition in Plants

MULTIPLE CHOICE QUESTIONS

1. Organisms which prepare food for themselves using simple naturally available raw materials are referred to as
(a) heterotrophs
(b) autotrophs
(c) parasites
(d) saprophytes

2. In the absence of which of the following will photosynthesis not occur in leaves?
(a) Guard cells
(b) Chlorophyll
(c) Vacuole
(d) Space between cells

3. Which of the following statements is/are correct?
(i) All green plants can prepare their own food.
(ii) Most animals are autotrophs.
(iii) Carbon dioxide is not required for photosynthesis.
(iv) Oxygen is liberated during photosynthesis.
Choose the correct answer from the options below:
(a) (i) and (iv)
(b) (ii) only
(c) (ii) and (iii)
(d) (i) and (ii)

4. Pitcher plant traps insects because it
(a) is a heterotroph.
(b) grows in soils which lack in nitrogen.
(c) does not have chlorophyll.
(d) has a digestive system like human beings.

5. The term that is used for the mode of nutrition in yeast,
mushroom and bread-mould is
(a) autotrophic
(b) insectivorous
(c) saprophytic
(d) parasitic

6. When we observe the lower surface of a leaf through a magnifying lens we see numerous small openings. Which of
the following is the term given to such openings?
(a) Stomata
(b) Lamina
(c) Midrib
(d) Veins

7. Two organisms are good friends and live together. One provides shelter, water, and nutrients while the other prepares and provides food. Such an association of organisms is termed as
(a) saprophyte
(b) parasite
(c) autotroph
(d) symbiosis

8. Which of the following raw material is available in the air for photosynthesis?
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Hydrogen

VERY SHORT ANSWER QUESTIONS

9. Potato and ginger are both underground parts that store food. Where is the food prepared in these plants?
10. Photosynthesis requires chlorophyll, and a few other raw materials. Add the missing raw materials to the list given below:
Water, minerals, a)_____________, b)______________.

SHORT ANSWER QUESTIONS

11. A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves?

12. Unscramble the following to form terms related to modes of nutrition.
(i) RASPAEIT
(ii) ROPEHYTSAP
(iii) TOROPHAUT
(iv) SIBIOMSYS

13. Nitrogen is an essential nutrient for plant growth. But farmers who cultivate pulse crops like green gram, bengal gram, black gram, etc. do not apply nitrogenous fertilizers during cultivation. Why?
14. Wheat dough if left in the open, after a few days, starts to emit a foul smell and becomes unfit for use. Give reason.
15. Sunlight, chlorophyll, carbon dioxide, water and minerals are raw materials essential for photosynthesis. Do you know where they are available? Fill in the blanks with the appropriate raw materials.
(a) Available in the plant : _______________
(b) Available in the soil : _______________, _______________
(c) Available in the air : _______________
(d) Available during day : _______________

16. Observe the diagram given as Figure 1.1 and label the following
terms given in the box.

LONG ANSWER QUESTIONS

17. Match the organisms given in Column I with their mode of nutrition given in Column II.

Column I Column II
a) Mango Tree 1) Insectivorous plants
b) Mushroom 2) Heterotroph
c) Pitcher Plant 3) Autotroph
d) Cuscuta4 4) Saprophyte
e) Elephant 5) Parasitic

18. Wild animals like tiger, wolf, lion and leopard do not eat plants. Does this mean that they can survive without plants? Can you provide a suitable explanation?

19. Fill in the blanks of the paragraph given below with the words provided in the box.

chlorophyll, energy, food, carbon dioxide, water, photosynthesis
Note: A word can be used more than once.
Leaves have a green pigment called (a) which captures (b) from sunlight. This (c) is used in the process of (d) and along with other raw materials like (e) and (f) synthesize (g).

 

20. Can you give me a name?

Solve each of the following riddles by writing the name of
the organism and its mode of nutrition. One riddle is solved
to help you.

(a) I am tall but I cannot move. I am green and can prepare
my own food. tree, autotroph
(b) I live in water; people keep me in an aquarium and
feed me.
(c) I am small and I can fly. I disturb your sleep, bite you
and suck your blood which is my food.
(d) I am white and soft. I grow well in the rainy season.
Children pluck me from the ground and admire me. I
absorb nutrients from decomposed dead parts of
plants and animals in the soil.

Chapter 2: Nutrition in animals

MULTIPLE CHOICE QUESTIONS

1. Given below from (i) to (iv) are some food items.
(i) Boiled and mashed potato
(ii) Glucose solution
(iii) A slice of bread
(iv) Mustard oil
Which of the above will give blue-black colour when tested
with iodine?
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)

2. Which of the following pair of teeth differ in structure but are
similar in function?
(a) canines and incisors.
(b) molars and premolars.
(c) incisors and molars.
(d) premolars and canines.

3. Read carefully the terms given below. Which of the following set is the correct combination of organs that do not carry out any digestive functions?
(a) Oesophagus, Large Intestine, Rectum
(b) Buccal cavity, Oesophagus, Rectum
(c) Buccal cavity, Oesophagus, Large Intestine
(d) Small Intestine, Large Intestine, Rectum

4. The swallowed food moves downwards in the alimentary canal because of
(a) force provided by the muscular tongue.
(b) the flow of water taken with the food.
(c) gravitational pull.
(d) the contraction of muscles in the wall of food pipe.

5. The acid present in the stomach
(a) kills the harmful bacteria that may enter along with the
food.
(b) protects the stomach lining from harmful substances.
(c) digests starch into simpler sugars.
(d) makes the medium alkaline.

6. The finger-like outgrowths of Amoeba helps to ingest food. However, the finger-like outgrowths of human intestine helps to
(a) digest the fatty food substances.
(b) make the food soluble.
(c) absorb the digested food.
(d) absorb the undigested food.

7. Read the following statements with reference to the villi of the small intestine.
(i) They have very thin walls.
(ii) They have a network of thin and small blood vessels close to the surface.
(iii) They have small pores through which food can easily pass.
(iv) They are finger-like projections.
Identify those statements which enable the villi to absorb digested food.
(a) (i), (ii) and (iv)
(b) (ii), (iii) and (iv)
(c) (iii) and (iv)
(d) (i) and (iv)

8. The false feet of Amoeba are used for
(a) movement only.
(b) capture of food only.
(c) capture of food and movement.
(d) exchange of gases only.

9. The enzymes present in the saliva convert
(a) fats into fatty acids and glycerol.
(b) starch into simple sugars.
(c) proteins into amino acids.
(d) complex sugars into simple sugars.

10. Cud is the name given to the food of ruminants which is
(a) swallowed and undigested.
(b) swallowed and partially digested.
(c) properly chewed and partially digested.
(d) properly chewed and completely digested.

11. Choose the correct order of terms that describes the process of
nutrition in ruminants.
(a) swallowing → partial digestion → chewing of cud → complete digestion
(b) chewing of cud → swallowing → partial digestion → complete digestion
(c) chewing of cud → swallowing → mixing with digestive juices → digestion
(d) swallowing → chewing and mixing → partial digestion → complete digestion

12. Cellulose-rich food substances are good source of roughage in
human beings because
(a) human beings do not have cellulose-digesting enzymes.
(b) cellulose gets absorbed in the human blood and converts
into fibres.
(c) the cellulose-digesting bacteria convert cellulose into
fibres.
(d) cellulose breaks down into smaller components which
are egested as roughage.

VERY SHORT ANSWER QUESTIONS

13. Name the parts of the alimentary canal where
(i) water gets absorbed from undigested food.
(ii) digested food gets absorbed.
(iii) taste of the food is perceived.
(iv) bile juice is produced.

14. Mark the following statements as True or False. If false, write
the correct statements.
(a) Tongue is attached to the roof of the mouth cavity at the
back.
(b) The large intestine is longer and wider than the small
intestine of the human alimentary canal.
(c) Mucus protects the stomach lining from damage.
(d) All heterotrophs have a similar basic process of nutrition.

15. Choose the odd one out from each group and give reasons.
(i) liver, salivary gland, starch, gall bladder
(ii) stomach, liver, pancreas, salivary gland
(iii) tongue, absorption, taste, swallow
(iv) oesophagus, small intestine, large intestine, rectum

16. You were blindfolded and asked to identify the drinks provided in two different glasses. You could identify drink A as lime juice and B as bitter gourd juice. How could you do it inspite of being blindfolded?

17. Fill in the blanks with suitable words:
(a) The alimentary canal stretches from ____ to ____
(b) Teeth are rooted in separate ___ in between the ____
(c) Digestion of food starts in ___ and gets completed in ___
(d) ___ is the largest gland in the human body.

18. Following statements describe the five steps in animal nutrition. Read each statement and give one word for each statement. Write the terms that describes each process.
(a) Transportation of absorbed food to different parts of body
and their utilisation.
(b) Breaking of complex food substances into simpler and
soluble substances.
(c) Removal of undigested and unabsorbed solid residues
of food from the body.
(d) Taking food into the body.
(e) Transport of digested and soluble food from the intestine
to blood vessels.

SHORT ANSWER QUESTIONS

19. Match the animals in Column I with their mode of feeding
listed in Column II

Column I Column II
Animals Mode of Feeding
a) Housefly 1) Biting and Chewing
b) cockroach 2) Suckling
c) Mosquito 3) Sponging
d) Infants 4) Sucking

20. Boojho took some grains of boiled rice in test tube ‘A’ and Paheli took boiled and chewed rice in test tube ‘B’. Both of them poured 1 – 2 drops of iodine solution into the test tube and observed the colour change. What colour change would they have observed? Give reasons for your answer.

21. ‘A’ got her gall bladder removed surgically as she was diagnosed with stones in her gall bladder. After the surgery, she faced problems in digestion of certain food items when consumed in bulk. Can you tell which kind of food items would they be and why?

22. Match the organs in Column I with the words listed in Column II.

Column I Column II
a) Rectum 1) Mucous
b) Gall Bladder2) 2) Villi
c) Stomach 3) Taste Buds
d) Tongue 4) Faeces
e) Small Intestine 5) Bile juice

23. Ruminants such as cows and buffaloes swallow their food hurriedly and then sit restfully and chew their food. Can you reason why?

24. Boojho and Paheli were eating their food hurriedly so that they could go out and play during the recess. Suddenly, Boojho started coughing violently. Think of the reasons why he was coughing and discuss with your friends.

LONG ANSWER QUESTIONS

25. Fill in the blanks using the words listed below.
water, front, intestinal, salts, pseudopodia, back, vacuole
(a) The digestion of all food components is completed by the ____________ juice.
(b) Large intestine absorbs ___________ and some __________ from the undigested food.
(c) Tongue is attached at the _____________ to the floor of the mouth cavity and is free at the _____________.
(d) Amoeba pushes out _____________ around the food and traps it in a food _____________.

26. Label the below given Figure 2.1 as directed below in (i) to (iv) and give the name of each type of teeth.
(i) The cutting and biting teeth as ‘A’
(ii) The piercing and tearing teeth as ‘B’
(iii) The grinding and chewing teeth as ‘C’
(iv) The grinding teeth present only in adult as ‘D’

27. Read the following passage carefully and answer the questions
that follows it.
Bile juice is stored in a sac called, gall bladder, located near its organ of secretion, liver. The gall bladder releases the bile juice into the small intestine whenever food reaches there. Though bile juice is devoid of any digestive enzymes, it is required for the digestion of fats. The fats cannot be digested easily because they are insoluble in water and are present as large globules. Bile juice breaks down big fat droplets into smaller droplets.
These are then easily digested by the enzymes released from the pancreas.
(a) Which organ secretes the bile juice?
(b) Why is digestion of fats difficult as compared to that of
other nutrients?
(c) How does bile juice help in digestion of fat?
(d) Where is the digestion of fat completed?
(e) Does bile juice digest fat completely?

28. Label the following parts in Figure 2.2 and name them.
(a) The largest gland in our body.
(b) The organ where protein digestion starts.
(c) The organ that releases digestive juice into the small
intestine.
(d) The organ where bile juice gets stored.

29. Open your mouth, look into a mirror and try to count the different types of teeth in your mouth. Compare them with Figure 2.3 on page 13 of your NCERT textbook. Record your observations in the table below:
(a) Did you observe any difference in the number of teeth? If yes, could you identify which type of teeth showed the
difference?
(b) Compare the number and type of teeth in an adult (say your parents or cousins who have reached the age
of 25–30 or more). Note your observation.

30. Solve the crossword given as Figure 2.3.

Across
1. Cream-coloured digestive gland
3. Undigested excretory solid residues
4. Organ that mixes saliva with the food
5. Point of defecation
7. Stored in gall bladder
10. Finger-like outgrowth in the small intestine
13. Kind of taste buds
14. Kills bacteria in the stomach

Down
2. Feeds with the help of pseudopodia
6. Total number of molars in one jaw of an adult
8. Largest gland
9. Watery secretion in the mouth
11. A ruminant
12. Form of food chewed by ruminants

Chapter 3: Fibre to Fabric

MULTIPLE CHOICE QUESTIONS

1. The rearing of silkworms for obtaining silk is called
(a) cocoon
(b) silk
(c) sericulture
(d) silviculture

2. Which of the following is not a type of silk?
(a) Mulberry silk
(b) Tassar silk
(c) Mooga silk
(d) Moth silk

3. Paheli wanted to buy a gift made of animal fibre obtained without killing the animal. Which of the following would be the right gift for her to buy?
(a) Woollen shawl
(b) Silk scarf
(c) Animal fur cap
(d) Leather jacket

4. Silk fibre is obtained from
(a) fleece of sheep
(b) cotton ball
(c) cocoon
(d) shiny jute stalk

5. Wool fibre cannot be obtained from which of the following?
(a) Goat
(b) Llama
(c) Alpaca
(d) Moth

6. Selective breeding is a process of
(a) selecting the offsprings with desired properties.
(b) selecting the parents with desired properties.
(c) selecting an area for breeding.
(d) selecting fine hair for good quality wool.

7. The general process that takes place at a sheep shearing shed is
(a) removal of fleece.
(b) separating hair of different textures.
(c) washing of sheep fibre to remove grease.
(d) rolling of sheep fibre into yarn.

8. The term sericulture is used for
(a) culture of bacteria.
(b) rearing of silkworm.
(c) making silk fabric from silk yarn.
(d) production of sarees.

9. Reeling of silk is
(a) a process of making silk reels.
(b) spinning of silk fibres.
(c) weaving of silk cloth.
(d) the process of taking silk threads from cocoon.

10. Silkworms secrete fibre made of
(a) fat
(b) cellulose
(c) protein
(d) nylon

VERY SHORT ANSWER QUESTIONS

11. Fill in the blanks in the following statements.
(a) _________ and _________ fibres are obtained from animals.
(b) Silk fibres come from _________ of silk _________.
(c) Wool yielding animals bear _________ on their body.
(d) Hair trap a lot of _________, which is a poor _________ of heat.

12. State whether the following statements are True or False. If false, correct them.
(a) Silkworms are caterpillars of silk moth.
(b) In India, camels and goats are generally reared for obtaining wool.
(c) The rearing of silkworms for obtaining silk is called silviculture.
(d) In the process of obtaining wool from fleece, sorting is done after scouring.
(e) Yak hair are not used to make woollen fabric.

13. How do the hair of certain animals help in keeping their bodies warm?

SHORT ANSWER QUESTIONS

14. Match the items of Column I with the items given in Column II.

Column I Column II
a) Yak wool 1) Sheared hair
b) Angora goats 2) Silkworm
c) Mulberry leaves 3) Tiber and Ladakh
d) Scouring4) 4) Jammu and Kashmir

15. Various steps involved to obtain wool from fleece are given here.
(i) Picking out the burrs
(ii) Dyeing in various colours
(iii) Shearing
(iv) Scouring
(v) Sorting
Write the above steps in the correct sequence in which they are
carried out.

16. Some words related with silk are jumbled up. Write them in
their correct form.
(a) TURECULRISE
(b) WILSMORK
(c) BELMURRY
(d) RINGLEE

17. Figure 3.1 shows three rings of circles with letters in them. Some of these letters in each ring can form the name of one wool yielding animal. Find the names of these animals. Fig. 3.1
18. Write a caption for each of the figures given as Figure 3.2 (a–d).

19. Steps for the production of silk are given below in a jumbled order. Arrange them in their proper sequence.
(a) Eggs are warmed to a suitable temperature for the larvae to hatch from eggs.
(b) Fibers are taken out from the cocoon.
(c) After 25 to 30 days, the caterpillars stop eating and start spinning cocoons.
(d) The larvae/caterpillars or silkworms are kept in clean trays along with freshly chopped mulberry leaves.
(e) Female silk moths lay eggs.
(f) Cocoons are kept under the sun or boiled in water.

20. A wholesale woollen fibre dealer gets the woollen fibre of different textures sorted for various purposes. Match the items in Column I with the woollen fibre in Column II.

Column I Column II
a) Pashmina Shawl 1) Camel Wool
b) Woollen Carpet 2) Angora Wool
c) Baby Blanket 3) Kashmir goat
d) Woollen Sweater 4) Sheep Wool

LONG ANSWER QUESTIONS

21. Complete the paragraph related to the life history of silk moth by filling in the blanks.
The ____(a)___ silk moth lays ___(b)___, from which hatch
____(c)___ called ___(d)____ or ___(e)____. They grow in size and
when the caterpillar is ready to enter the next stage of its life
history called ___(f)____, it first weaves a covering to hold itself,
which is known as ___(g)____.

22. Paheli went to the market to buy sarees for her mother. She took out a thread from the edge of the two sarees shown by the shopkeeper and burnt them. One thread burnt with a smell of burning hair and the other burnt with the smell of burning paper. Which thread is from a pure cotton saree and which one from a pure silk saree? Give reason for your answer.

23. Explain the phrase – “Unity is Strength” on the basis of the making of fabric from fibre.
24. Write various steps for processing fibres into wool.
25. Describe the life history of silk moth with the help of figures of various stages.

Chapter 4: Heat

MULTIPLE CHOICE QUESTIONS

1. A marble tile would feel cold as compared to a wooden tile on a winter morning, because the marble tile
(a) is a better conductor of heat than the wooden tile.
(b) is polished while wooden tile is not polished.
(c) reflects more heat than wooden tile.
(d) is a poor conductor of heat than the wooden tile.

2. A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because
(a) friction between the layers of newspaper produces heat.
(b) air trapped between the layers of newspaper is a bad conductor of heat.
(c) newspaper is a conductor of heat.
(d) newspaper is at a higher temperature than the temperature of the surrounding.

3. Paheli and Boojho measured their body temperature. Paheli found her’s to be 98.6 °F and Boojho recorded 37°C. Which of the following statement is true?
(a) Paheli has a higher body temperature than Boojho.
(b) Paheli has a lower body temperature than Boojho.
(c) Both have normal body temperature.
(d) Both are suffering from fever.

4. Boojho has three thermometers as shown in Figure 4.1. He wants to measure the temperature of his body and that of boiling water. Which thermometer (s) should he choose?


(a) Thermometer (i) or (iii) for measuring body temperature
and (ii) for measuring the temperature of boiling water.
(b) Thermometer (i) for measuring temperature of both.
(c) Thermometer (ii) for measuring temperature of both.
(d) Thermometer (iii) for measuring temperature of both.

5. Four arrangements to measure temperature of ice in beaker with laboratory thermometer are shown in Figure 4.2 (a, b, c and d). Which one of them shows the correct arrangement for accurate measurement of temperature?
6. Fig 4.3 (a–d) shows a student reading a doctor’s thermometer. Which of the figure indicates the correct method of reading temperature?

7. Figure 4.4. (a–d) shows the readings on four different thermometers. Indicate which of the reading shows the normal human body temperature?

VERY SHORT ANSWER QUESTIONS

8. Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
9. A laboratory thermometer A is kept 7 cm away on the side of the flame while a similar thermometer B is kept 7 cm above the flame of a candle as shown in Figure 4.5.

Fig. 4.5
Which of the thermometers, A or B, will show a greater rise in temperature? Give reason for your answer.

10. To keep her soup warm Paheli wrapped the container in which it was kept with a woollen cloth. Can she apply the same method to keep a glass of cold drink cool? Give reason for your answer.

11. In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object. What is the reason for this rise in the level of mercury?

SHORT ANSWER QUESTIONS

12. A circular metal loop is heated at point O as shown in Figure 4.6.
(i) In which direction would heat flow in the loop?
(ii) In which order the pins at points P,Q and R fixed with the help of wax fall if points O, P, Q and R are equidistant
from each other?
13. In the arrangements A and B shown in Figure 4.7, pins P and Q are fixed to a metal loop and an iron rod with the help of wax. In which case are both the pins likely to fall at different times? Explain.

14. For setting curd, a small amount of curd is added to warm milk. The microbes present in the curd help in setting if the temperature of the mixture remains approximately between 35°C to 40°C. At places, where room temperature remains much below the range, setting of curd becomes difficult. Suggest a way to set curd in such a situation.

15. You may have noticed that a few sharp jerks are given to clinical thermometer before using it. Why is it done so?

16. Why is it advised not to hold the thermometer by its bulb while reading it?

17. At a camp site there are tents of two shades – one made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter?

18. While constructing a house in a coastal area, in which direction should the windows preferably face and why?

19. Observe the picture given as Figure 4.8. Water is being boiled in a pan of wide base.
Fig. 4.8
(i) Which position P or T will feel warmer?
(ii) Fill up the boxes P and T to indicate the mode of flow of heat to the hand. 20. Look at Figure 4.9.
Fig. 4.9
The length of wire PQ in case of A is equal to the diameter of the semicircle formed by the wire CDE, in case B. One pin is attached to each wire with the help of wax as shown in Figure 4.9. Which pin will fall first? Explain.
(A) (B)

Chapter 5: Acids, Bases and Salts

MULTIPLE CHOICE QUESTIONS

1. The correct way of making a solution of acid in water is to
(a) add water to acid.
(b) add acid to water.
(c) mix acid and water simultaneously.
(d) add water to acid in a shallow container.

2. Products of a neutralisation reaction are always
(a) an acid and a base.
(b) an acid and a salt.
(c) a salt and water.
(d) a salt and a base.

3. Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would be observed
(a) Yellow in both acid and base.
(b) Yellow in acid and red in base.
(c) Pink in acid and yellow in base.
(d) Red in acid and blue in base.

4. Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are
(a) red and blue.
(b) blue and red.
(c) pink and colourless.
(d) colourless and pink

5. When the soil is too basic, plants do not grow well in it. To improve its quality what must be added to the soil?
(a) Organic matter
(b) Quick lime
(c) Slaked lime
(d) Calamine solution

6. ‘Litmus’, a natural dye is an extract of which of the following?
(a) China rose (Gudhal)
(b) Beetroot
(c) Lichen
(d) Blue berries (Jamun)

7. Neutralisation reaction is a
(a) physical and reversible change.
(b) physical change that cannot be reversed.
(c) chemical and reversible change.
(d) chemical change that cannot be reversed.

8. A solution changes the colour of turmeric indicator from yellow to red. The solution is
(a) basic
(b) acidic
(c) neutral
(d) either neutral or acidic

9. Which of the following set of substances contain acids?
(a) Grapes, lime water
(b) Vinegar, soap
(c) Curd, milk of magnesia
(d) Curd, vinegar

10. On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution?
(a) Basic
(b) Either acidic or basic
(c) Either acidic or neutral
(d) Either basic or neutral

11. Which of the following is an acid-base indicator?
(a) Vinegar
(b) Lime water
(c) Turmeric
(d) Baking soda

VERY SHORT ANSWER QUESTIONS

12. Look at the given reaction.
Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water

Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any).

13. State whether the following statements are true or false. Correct the false statements.
(a) All substances are either acidic or basic.
(b) A compound if acidic will turn all indicators red.
(c) Lime water turns red litmus blue.
(d) Common salt dissolved in water turns blue litmus red.
(e) Phenolphthalein is a natural indicator.
(f) Calamine can be used to treat ant’s sting.
(g) Lemon water is basic in nature.

14. Paheli is suffering from indigestion due to acidity. Is it advisable to give her orange juice in this situation and why?

SHORT ANSWER QUESTIONS

15. Look at Figure 5.1 which shows solutions taken in test tubes A,B,C and D. What colour is expected when a piece of red litmus paper is dropped in each test tube? Nature of the solutions is given in the table for your help.

Test Tube Nature of Solution Change in colour of red litmus
A Neutral
B Basic
C Acidic
D Neutral

 

16. While playing in a park, a child was stung by a wasp. Some elders suggested applying paste of baking soda and others lemon juice as a remedy. Which remedy do you think is appropriate and why?

17. Form a sentence using the following words – baking soda, ant bite, moist, effect, neutralised, rubbing.

18. Match the substances in Column I with those in Column II.

Column I Column II
a) Tartaric acid 1) soap
b) calcium hydroxide 2) curd
c) formic acid 3) unripe mangoes
d) sodium hydroxide 4) ant’s sting
e) lactic acid 5) lime water

19. Fill the blanks in the following sentences
(a) Lemon juice and vinegar taste ___________ because they contain ___________.
(b) Turmeric and litmus are _________ acid-base indicators.
(c) Phenolphthalein gives _________ colour with lime water.
(d) When an acidic solution is mixed with a basic solution, they _________ each other forming _________ and water.

LONG ANSWER QUESTIONS

20. Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of
solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results.

21. Fill in the cross word given as Figure 5.2 with the help of the clues provided.
Across
(2) The solution which does not change the colour of either red or blue litmus.
(4) Phenolphthalein gives pink colour in this type of solution.
(7) Colour of blue litmus in lemon juice.
Down
(1) It is used to test whether a substance is acidic or basic.
(3) It is a natural indicator and gives pink colour in basic
solution.
(5) Nature of ant’s sting.
(6) It is responsible for increase in temperature during a
neutralisation reaction.

22. A farmer was unhappy because of his low crop yield. He discussed the problem with an agricultural scientist and
realised that the soil of his field was either too acidic or too basic. What remedy would you suggest the farmer to neutralise the soil?
23. You are provided with four test tubes containing sugar solution, baking soda solution, tamarind solution, salt solution. Write down an activity to find the nature (acidic/basic/neutral) of each solution.
24. You are provided with three test tubes A, B and C as shown in Figure 5.3 with different liquids. What will you observe when you put
(a) a piece of blue litmus paper in each test tube.
(b) a piece of red litmus paper in each test tube.
(c) a few drops of phenolphthalein solution to each test tube.
25. Paheli observed that most of the fish in the pond of her village were gradually dying. She also observed that the waste of a factory in their village is flowing into the pond which probably caused the fish to die.
(a) Explain why the fish were dying.
(b) If the factory waste is acidic in nature, how can it be neutralised?
26. Explain two neutralisation reactions related to daily life
situation.

Chapter 6: Physical and Chemical Changes

Chapter 7: Weather, Climate and Adaptation of Animals to Climate

Chapter 8: Wind, Storm and Cyclone

Chapter 9: Soil

Chapter 10: Respiration in Organisms

Chapter 11: Transportation in Animals and Plants

Chapter 12: Reproduction in Plants

Chapter 13: Motion and Time

Chapter 14 : Electric current and its Effects

Chapter 15: Light

Chapter 16: Water: A Precious Resource

Chapter 17: Forests: Our Lifeline

Chapter 18: Wastewater Story

 

Mathematics NCERT Exemplar for Class 7

Unit 1: Integers

Unit 2: Fractions and Decimals

Unit 3: Data handling

Unit 4: Simple Equations

Unit 5: Lines and Angles

Unit 6: Triangles

Unit 7: Comparing Quantities

Unit 8: Rational Numbers

Unit 9: Perimeter and Area

Unit 10: Algebraic Expressions

Unit 11: Exponents and Powers

Unit 12: Practical Geometry symmetry and Visualising Solid Shapes

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