Changes around Us
Trending Questions
Explain in detail, how we can keep our surroundings clean.
Name two chemicals used to disinfect water.
- is calm and cloudless
- is cloudy and highly stormy
- is full of strong winds
- has high pressure
What are the types of chlorination?
- Rate at which water is absorbed by subsoil
- Rate at which air is absorbed by soil
- Rate at which air trickles into soil
- Rate at which water trickles down the soil
- spring forests
- summer forests
- autumn forests
- rainforests
- beech
- coconut
- maple
- oak
Letter to the Municipal Commissioner
Which of the following is a part of inorganic impurity in sewage?
Urea
Phosphates
Faeces
Vegetable waste
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?
(a), (b) and (c)
(b) and (c)
(a) and (d)
All four
- deciduous
- evergreen
- desert
- aquatic
What type of change is the melting of wax?
What is said to be a major component of wastewater?
- Cleaning of closed drainage is easier than open drainage.
- Closed drainage prevents human exposure to harmful waste.
- Closed drainage is cheaper to build than open drainage.
- No wastewater treatment is needed for closed drainage.
Organic matter is decomposed by __________ bacteria in aeration tanks.
Which of the following reaction(s) involves absorption of light to initiate?
Respiration
Photosynthesis
Combustion
Photochemical decomposition
Give reasons for the following:
b. Moulding a wet clay pot is a reversible change but once a clay pot is baked, it is an irreversible change.
Chlorination is done to remove the foul smell of water.
- True
- False
What do you understand by water absorption rate?
It took 60 minutes for 360 mL of water to percolate through a soil sample. What is the rate of percolation for the soil sample? [5 MARKS]
O horizon is a main part of the soil. Could you please tell me why it is not mentioned in the textbook.
Give reasons for the following
(a) Separation of gases from the air is a physical change.
- 10 mL/min
- 10 mL/s
- 20 mL/s
- 25 mL/min
Water coming from industries is called __________.
sludge
sewage
effluent
Agriculture
15)
Assertion - Fuse wire is made up of an alloy constituted by lead and tin made by 1:1 ratio by mass
Reason - Both lead and tin have comparatively lower melting point than other metals.
Both (A) and (R) are true and (R) is the correct reason for (A)
Both (A) and (R) are true but (R) is not the correct explanation for (A)
(A) is true but (R) is false
(A) is false but (R) is true.
Name the following
A metal that rusts easily.
It was Paheli’s birthday, her brother Simba was helping her to decorate the house for the birthday party and their parents were also busy making other arrangements. Following were the activities going on at Paheli’s home: (i) Simba blew balloons and put them on the wall. (ii) Some of the balloons got burst. (iii) Paheli cut colorful strips of paper and put them on the wall with the help of tape. (iv) She also made some flowers by origami (paper folding) to decorate the house. (v) Her father made dough balls. (vi) Mother rolled the dough balls to make puries. (vii) Mother heated oil in a pan. (viii) Father fried the puries in hot oil. Identify the activities at Paheli’s home as those that can be reversed and those which cannot be reversed.
Give one word or a phrase for each of the following.
Reddish-brown powder on the surface of iron
Classify the following as physical or chemical change.
Chopping up wood
