MyClass24 logo
myclass24
YOUR CLASS. YOUR PACE.
Q&A Bank

Questions & Answers

388 answers across all subjects

Subject:MathematicsScienceEnglishSocial StudiesHindiPhysicsChemistryBiologyComputer Science
Class:123456789101112
ScienceClass 7CBSE

Name two alternative arrangements for sewage disposal where there is no sewerage system.

Soln: (i) Septic tanks (ii) Composting pits

ScienceClass 7CBSE

Animal waste, oil and urea are some of the organic impurities present in sewage. Name two more organic impurities present in sewage.

Soln: Fruits, Vegetables

ScienceClass 7CBSE

Name two inorganic impurities present in sewage.

Soln: Nitrates, Phosphates

ScienceClass 7CBSE

How are open drains harmful to human health?

Soln: The opening draining system causes problems with the foul smell. An open drainage system is the breeding sources for mosquitos and flies. The open drainage system also helps the growth of disease-causing organisms. Hence drains are harmful to human health.

ScienceClass 7CBSE

Why are open drains a concern?

Soln: Because it creates unhygienic and unsanitary conditions because of which it leads to the spread of disease.

ScienceClass 7CBSE

Which of the following is not a source of wastewater? (a) Sewers (b) Homes (c) Industries (d) Hospitals

Soln: The answer is (a) Sewers Explanation: Sewers are a network of big and small pipes that carries sewage from the point of being produced to the point of disposal, i.e. treatment plant.

ScienceClass 7CBSE

In a filtration, plant water is filtered using layers of (a) sand and clay. (b) clay and fine gravel. (c) sand and fine gravel. (d) sand, fine gravel and medium gravel.

Soln: The answer is (d) sand, fine gravel and medium gravel. Explanation: During wastewater treatment wastewater is allowed to enter a grit of sand, fine gravel and medium gravel. Here the speed of wastewater is slowed down to allow sand, fine gravel and medium gravel to settle down.

ScienceClass 7CBSE

Which of the following is a part of inorganic impurities of the sewage? (a) Pesticides (b) Urea (c) Phosphates (d) Vegetable waste

Soln: The answer is (c) Phosphates Explanation: Pesticides, urea and vegetable waste ate the organic waste that acts as impurities in sewage water whereas phosphates are the inorganic impurities present in sewage.

ScienceClass 7CBSE

The system of a network of pipes used for taking away wastewater from homes or public buildings to the treatment plant is known as (a) sewers. (b) sewerage. (c) transport system. (d) treatment plant.

Soln: The answer is (b) sewerage.

ScienceClass 7CBSE

Pick from the following one chemical used to disinfect water. (a) Chlorine (b) Washing soda (c) Silica (d) Coal

Soln: The answer is (a) Chlorine Explanation: Chorine is used to killing harmful organisms and the process of adding chlorine is called as chlorination.

ScienceClass 7CBSE

Water polluted by various human activities causes a number of water-borne diseases. Which of the following is not a waterborne disease? (a) Cholera (b) Typhoid (c) Asthma (d) Dysentry

Soln: The answer is (c) Asthma Explanation: Asthma is airborne disease whereas Cholera, Typhoid and dysentery are spread by contaminated water and food.

ScienceClass 7CBSE

An open-drain system is a breeding place for which of the following. (a) Flies (b) Mosquitoes (c) Organisms which cause diseases (d) All of these

Soln: The answer is (d) All of these Explanation: The opening draining system causes problems with the foul smell. The open drainage system is the breeding sources for mosquitos and flies. The open drainage system also helps the growth of disease-causing organisms.

ScienceClass 7CBSE

Which of the following is/are products of wastewater treatment? (a) Biogas (b) Sludge (c) Both biogas and sludge (d) Aerator

Soln: The answer is (c) Both biogas and sludge Explanation: During wastewater, treatment water is allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.

ScienceClass 7CBSE

Sewage is mainly a (a) liquid waste. (b) solid waste. (c) gaseous waste. (d) mixture of solid and gas.

Soln: The answer is (a) liquid waste. Explanation: Sewage water is the wastewater that includes domestic and industrial liquid wastes. It contains various suspended solids and harmful microorganisms.

ScienceClass 7CBSE

Which of the following is wastewater? (a) Water trickling from a damaged tap. (b) Water coming out of a shower. (c) Water flowing in a river. (d) Water coming out of laundry.

Soln: The answer is (d) Water coming out of laundry. Explanation: Water discharged during after routine works like washing clothes, flushing toilet, cleaning utensils makes the water dirty. This water is called as wastewater. Water coming out of the damaged tap, water coming out of shower and water flowing in a river are not dirty hence water coming out of a laundry is the right answer.

ScienceClass 7CBSE

Read the following passage carefully and answer the questions that follow it. Bile juice is stored in a sac called the gallbladder, located near its organ of secretion, the 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 the digestion of fats difficult as compared to that of other nutrients? (c) How does bile juice help in the digestion of fat? (d) Where is the digestion of fat completed? (e) Does bile juice digest fat completely?

Soln: (a) Liver (b) Insolubility of fat in water. (c) Breaks down big fat droplets into smaller droplets. (d) Small intestine (e) No

ScienceClass 7CBSE

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.

Soln: Sometimes, when one eats hurriedly, talks or laughs while eating, the flap-like valve, epiglottis, closing the passage of the windpipe, remains open. The food may enter the windpipe and coughing helps to clear it.

ScienceClass 7CBSE

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

Soln: To digest the food completely, ruminants keep the food as cuds.

ScienceClass 7CBSE

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

Soln: Those foods will be fats because of bile juice present in the gall bladder helps in the digestion of fat. Removal of gall bladder makes it hard to digest the fat.

ScienceClass 7CBSE

Boojho took some grains of boiled rice in a test tube ‘A’, and Paheli took boiled and chewed rice in a 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.

Soln: In test-tube A colour of iodine changes to blue-black because of the reaction of iodine with starch. In test-tube B colour will not change because salivary amylase acts on starch while chewing, reducing it to simpler sugars.

12345678910