Answers of Class 7 Science Chapter 18 – Wastewater Story

Question 1: Fill in the blanks:

(a) Cleaning of water is a process of removing _______.

(b) Wastewater released by houses is called ________.

(c) Dried _______ is used as manure.

(d) Drains get blocked by ________ and ________.

Answer 1 (a) Cleaning of water is a process of removing __pollutants__.

(b) Wastewater released by houses is called __sewage__.

(c) Dried __sludge__ is used as manure.

(d) Drains get blocked by __cooking oil__ and __fats__.

Question 2: What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer 2: Sewage is the wastewater containing both liquid and solid wastes produced by human activities from homes, industries, hospitals, offices, etc.

Sewage contains various contaminants including disease-causing bacteria and other microbes. If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. 

If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. which may lead to death. That is why it is harmful to discharge untreated sewage into rivers or seas.

Question 3: Why should oils and fats be not released in the drain? Explain.

Answer 3: Oils and fats harden and block the sewage pipes. In an open drain also, fats block porosity of soil which affects its water filtering efficiency. That is why oils and fats should not be released in the drain.

Question 4: Describe the steps involved in getting clarified water from wastewater.

Answer 4: The steps involved in getting clarified water from wastewater are as follows:

(i) Use an aerator to bubble air through the wastewater. A mechanical stirrer or a mixer can also be used in place of the aerator. This helps in reducing bad odour of the wastewater.

(ii) Then, the water is filtered through the layers of sand, fine gravel, and medium gravel. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear.

(iii) Then any disinfectant such as chlorine tablet is added to the filtrate and stirred to obtain completely clear water.

Question 5: What is sludge? Explain how it is treated.

Answer 5: Semi-solids such as faeces that settle down during wastewater treatment are called sludge. This sludge is removed using a scraper and then transferred to a tank where it is decomposed by anaerobic bacteria to produce biogas. This biogas is used as a low-cost fuel for heating, cooking, etc. It is also used to produce electricity.

Question 6: Untreated human excreta is a health hazard. Explain.

Answer 6: Untreated human excretions are a health hazard. 

It causes pollution of soil and water including the underground water. 

Thus, it contaminates the sources of water from which people collect water for drinking and household purposes. 

When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc., which may even lead to death.

Question 7: Name two chemicals used to disinfect water.

Answer 7: Two chemicals used to disinfect water are chlorine and ozone.

Question 8: Explain the function of bar screens in a wastewater treatment plant. 

Answer 8:  Bar screen
In a wastewater treatment plant, bar screen removes large solid objects from water. The wastewater is allowed to pass through bar screen so that large solid objects such as rags, napkins, sticks, cans, plastic bags, polythene, etc. present in wastewater can be removed.

Question 9: Explain the relationship between sanitation and disease.

Answer 9: Sanitation and disease are related to each other as lack of sanitation can cause diseases.
In our country, a large number of people even today do not have sewerage facilities and thus defecate in open fields, railway tracks, etc.

The untreated human excreta thus pollute soil and water sources including the underground water. 

When this contaminated water is used for drinking, it can cause diseases such as cholera, typhoid, hepatitis, dysentery, etc. which may even lead to death.

Therefore, lack of sanitation resulting in drinking of contaminated water can cause health problems.

Question 10: Outline your role as an active citizen in relation to sanitation.

Answer 10: A citizen has many responsibilities regarding sanitation. Among other things, an active citizen should do the following with regard to maintaining proper sanitation:

(i) Ensure that his surroundings (both inside and outside home) are clean.

(ii) Ensure that the sewerage system in his house is properly managed.

(iii) If he notices some leakage or other problem in the sewerage system, he should report it to the municipality.

Question 11: Here is a crossword puzzle: Good luck!

Across

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body

Down

1. Used water

2. A pipe carrying sewage

5. Micro-organism which causes cholera

7. A chemical to disinfect water

Answer 11: 

Question 12: Study the following statements about ozone:

(a) It is essential for breathing of living organisms.

(b) It is used to disinfect water.

(c) It absorbs ultraviolet rays.

(d) Its proportion in air is about 3%.

Which of these statements are correct?

(i) (a), (b) and (c)

(ii) (b) and (c)

(iii) (a) and (d)

(iv) All four

Answer 12: (ii) (b) and (c)

CBSE Class 7 Science Sample Test Paper From Chapter 2 – Nutrition In Animals

M.M: 76 marks                                                   Dated: 28/07/2011

Time: 1 hour 15 minutes                                                                   

Q 1:  Fill in the blanks      (1 mark each question x = 30 = 30 marks)

1. The breakdown of complex components of food into simpler substances is called _____________.
2. ______ ______ are the first set of teeth that grows during infancy and fall off at the age of between six to eight years.
3. The process of taking food into the body is called ________.
4. Starfish feeds on animals covered by hand shells of ___________  _______________
5. The food passes through a continuous canal which begins at ________  _______ and ends at the _________.
6. The digestive tract and the associated glands together constitute the _________ ___________.
7. In human body, the ___________ breaks down the starch into sugars.
8. ________ ________ is a special long thread that is moved between two teeth to take out trapped food particles.
9. The _______ carries air from the nostrils to the lungs.
10. ___________ is a thick walled bag, shaped like flattened U and is the widest part of the alimentary canal.
11. The _________ protects the lining of the stomach.
12. The _______ kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps digestive juices to act.
13. The digestive juices break down the ____________ into simpler substances.
14. The process of removal of faecal matter through the anus of human body is called __________.
15. The ______ ____________ is highly coiled and is about 7.5m long.
16. _________ secretes bile juice that is stored in a sac called the gall bladder.
17. The ______ plays an important role in the digestion of fats.
18. The _______ juice acts on carbohydrates, fats and proteins and changes them into simpler substances.
19. The inner walls of the small intestine have thousands of finger-like outgrowths called ________.
20. ____________ is the process in which the absorbed substances are transported via the blood vessels to different organs of the body.
21. Grass eating animals quickly swallow the grass and store in a part of the stomach called _________.
22. ORS stands for __________ __________ ____________.
23. The salivary glands secrete a watery liquid called ______________.
24. The food coming from the mouth is pushed down by alternate contraction and relaxations of muscles in Oesophagus, this process is called ___________.
25. A long tube of 8 to 9 m length running from mouth to anus is called ____________ __________.
26. The __________ runs adjacent to the food pipe in the body.
27. The ________ teeth are for piercing and tearing the food.
28. The white hard outer covering of tooth is called __________.
29. The part of tooth below the enamel is called _________
30. The total number of teeth in an adult is _______.

Q 2: Define nutrition. Write the names of five processes involved in nutrition in human body.                                                        (3 marks)

Q 3: From front to back, write the number of teeth and their names present in the lower jaw of human adult.                              (4 marks)

Q 4: What is the name of the second set of teeth that may last throughout or fall off during old age or due to some dental disease?   (1 mark)

Q 5: Write the names of parts that together form the digestive tract.  (3 marks)

Q 6: Write two functions of tongue in human body.             (2 marks)

Q 7: What do you understand by tooth decay? Write four major culprits of tooth decay.                                                          (3 marks)

Q 8: Which is the largest gland in human body? What is its colour?   (2 marks)

Q 9: Define absorption. Where does it happen?                    (2 marks)

Q 10: What is role of villi in intestine in human body?          (1 mark)

Q 11: In small intestine, the intestinal juice breaks the following in to what:                                                                                       (3 marks)

1. Carbohydrate
2. Fats
3. Proteins

Q 12: Between large intestine and small intestine, which is 
           i). wider?                                                                                              ii). lengthier?                                                                 (2 marks)

Q 13: What is the function of large intestine in human body?  
(1 mark)

Q 14: What happens during breakdown of glucose? What are the end products?                                                                               (2 marks)

Q 15: What is a symptom of diarrhoea? Write one cause of it. Can diarrhoea be neglected completely? Why or why not?          (4 marks)

Q 16: With the help of a labelled diagram, explain how feeding of food, digestion and throwing out happens in Amoeba?         (5 marks)

Q 17: Write True or False. In case of false statement, write the correct statement.                                             (1 mark x 7 = 7 marks)

1. The basic process of digestion of food and release of energy is completely different in all animals - __________
2. Pseudopodia means real feet - __________
3. Formation of faeces happens in small intestine ___________
4. Killing of bacteria in human body happens in liver - ________
5. Release of faeces is done by Rectum - _________
6. Amoeba has a fixed shape - ___________
7. Undigested and unabsorbed food is expelled out of the body as faeces by large intestine - __________

Q 18: How many taste buds are there in human tongue? Name them. (2 marks)

Science Class 7th Project On Information On Wool Yielding Animals From Chapter Fibres to Fabrics

Science Class 7th Project On Information On Wool Yielding Animals From Chapter Fibres to Fabrics

S. No.	Name of the wool yielding animal	Picture	Information – Where it is found and what kind of wool does it provide etc.
1.	Lohi Sheep		Found in Rajasthan and Punjab, India. Gives good quality of wool that is used for making woollen clothes.
2.	Rampur Bushair Sheep		Found in Uttar Pradesh, Himachal Pradesh, India. Gives brown coloured superior carpet quality wool that is used for making nice quality of carpets.
3.	Nali Sheep		Found in Rajasthan, Haryana, and Punjab, India. Gives good quality of carpet wool that is used for making premium variety of carpets.
4.	Bakharwal Sheep		Found in Jammu and Kashmir, India. The wool given by Bakharwal sheep is used for making woollen shawls.
5.	Drysdale Sheep		Found in New Zealand. Gives coarse thick wool which is used in making carpets.
6.	Baluchi		Found in Iran, Pakistan and Afghanistan. Gives light brown carpet wool that is coarse and is used for making carpets.
7.	Angora goat		Found in Angora, Turkey. Produces fine quality of white or coloured wool called mohair.  Mohair is used in making carpets, scarves, winter hats, suits, sweaters, coats and socks.
8.	Llama camel		Found in Andes mountain region of South America. The wool of Llama camel is light weight, grease free, luxurious and soft and thus is used for great quality of woollen clothes.
9.	Alpaca camel		Found in Peru and other areas of South America. Alpaca camel wool is very fine and of yarn quality and so it is used for shawls, stoles and carpets.
10.	Yak		Found in Ladakh, Nepal and Sikkim in India and also in other parts of the world. The outer wool of Yak is rough whereas the inner wool is soft.  Wool from Yak is used to make blanket, socks, hats and sweaters etc.

Science Class VIIth Test From Chapter 13 – Motion and Time

M.M: 43 marks                           Date: 18/06/2011 Time: 1 hour 15 minutes

Q 1: Write True or False for the give statements, also correct the false statements.  (1 mark per question x 10 = 10 marks)

i. In ancient times, measurement of time was done by watches –
ii. A day has 8,640 seconds –
iii. The body moving in a curved line is said to have curvilatory motion –
iv. The time taken for one oscillation is called time gap –
v. Time = (Speed) / (Distance) -
vi. The basic unit of speed is km./min. –
vii. The time period of a pendulum is constant –
viii. The symbols of all the units of distance and time etc. is written in plural –
ix. By only knowing the distance covered by two bodies, it can be found which is faster –
x. If the distance-time graph of an object is a horizontal line parallel to the time axis, then the object is moving at constant speed -

Q 2: Fill in the blanks (1 mark per question x 13 = 13 marks, more than one word may come at certain blanks).

i. The point of intersection of ____________ and ___________ is called origin.
ii. The __________ of an object can be obtained from the distance-time graph.
iii. A __________ ________ is a diagram which shows the percentage composition of something in the form of slices of a circle.
iv. A ________ measures time by the position of the shadow cast by the Sun.
v. Sand clock is also known as _________________.
vi. 10 ___________ = 1 century.
vii. 10 centuries = 1 _____________
viii. Clocks are based on the principle of ______________ motion.
ix. The time-period of a pendulum depends on its _____________.
x. One complete to-and-fro movement of the pendulum bob is called an _____________.
xi. The maximum displacement of the bob form its mean position on either side is called the _____________ of pendulum.
xii. The quartz clocks and watches can be two types: _____________ and __________________.
xiii. The smallest time interval that can be measured with commonly available clocks and watches is ________________.

Q 3: Which of the two is a bigger unit of time: microsecond or nanosecond?                     (1 mark)

Q 4: What is the smallest time interval which can be measured accurately with clocks and watches used in Sports Meets?                                (1 mark)

Q 5: A pendulum takes 270 seconds for 18 complete oscillations. What is the time-period of this pendulum?                                         (2 marks)

Q 6: Calculate the number of seconds in one year.          (2 marks)

Q 7: The given figure shows the distance time graph for the motion of two vehicles A and B. Which one of them has faster speed?       (2 marks)

Distance Time graph

Q 8: Out of a line graph, a pie chart and a bar graph, which one will be suitable for the given cases:                                            (3 marks)

i. Runs scored in various over of a cricket match.
ii. Percentage composition of air
iii. Distance covered by a truck with time.

Q 9: A bus starts from rest at 9 AM. The distances covered by the bus at various instants of time are given below.                                             (3 marks)

Distance (km)	0	25	50	75	100
Time (AM)	9	09:30	10:00	10:30	11:00

i. Draw the distance-time graph for the bus.
ii. What was the distance covered by the bus at 10:45 AM?

Q 10: A sprinter attains a maximum speed of 12 m/sec. Calculate his speed in:                  (2 marks)

i. km/hr
ii. mm/sec

Q 11: What is meant by uniform and non uniform motion? Give an example of each.           (2 marks)

Q 12: A car moves with a speed of 50 km/hr for 15 minutes and then with a speed of 70 km/hour for the next 15 minutes. Find the total distance covered by the car.                                   (2 marks)