Different zones of a candle flame are marked by the letters P, Q, R and S.
Which of the following statements are correct?
(i) P is the luminous zone and is the hottest part of candle flame.
(ii) In zone Q, there is inadequate supply of oxygen.
(iii) Zone R contains unburnt wax vapours produced by melting of wax.
(iv) In S zone, carbon monoxide burns with a blue flame.
A (i) and (ii) only
B (ii), (iii) and (iv) only
C (ii) and (iv) only
D (i), (ii) and (iii) only
Which of the following statements are true?
I. Yellow flames are ideal for heating.
II. The substances which vaporise during burning give flames.
III. Luminous zone contains unburnt carbon particles.
IV. The non-luminous zone has highest temperature.
A I, II and III
B I, II and IV
C II, III and IV
D I, III and IV
In an experiment, 4.5 kg of a fuel was completely burnt. The heat produced was 180,000 kJ. The calorific value of the fuel is
A 180,000 kJ
B 40,000 kJ
C 40,000 kJ/kg
D 180,000 kJ/kg
How has the use of CNG in automobiles reduced the pollution in cities?
A It produces less amount of sulphur dioxide and chlorine.
B It does not leave any residue or smoke after burning in the engine.
C It produces large amount of carbon dioxide.
D It is used in compressed form.
Which of the following are possible advantages of using bacteria in sewage treatment?
(i) Bacteria multiply quickly, thus producing a cheap and abundant source of enzymes.
(ii) Only one type of bacteria is required to provide the various enzymes necessary for different kinds of wastes.
(iii) Bacteria can break down waste under anaerobic or aerobic condition.
A (i) only
B (i) and (iii) only
C (ii) and (iii) only
D (i), (ii) and (iii)
is only one kind of bacteria required to provide the various enzymes necessary for different kinds of wastes?because it was given so in the summary but in the solution it is showing this statement as false
Manisha took some vinegar in a test tube and added some baking powder to it. Then she lit a matchstick and brought it near the mouth of the test tube. The flame of matchstick got extinguished.
Which of the following is correct conclusion regarding the given experiment?
A Carbon dioxide gas does not support burning.
B Air contains carbon dioxide.
C Oxygen gas present in the air is necessary for burning.
D Oxygen gas can extinguish fire.
Raveena covered a beaker of boiled water with a metal tray as shown in the diagram.
The beaker and metal tray were then removed from the tripod stand and left on the table. After two minutes, which of the following can be observed?
A Water droplets are seen on the outer part of metal tray.
B Water droplets are seen on the inner part of tray and inner part of the beaker.
C Water droplets are seen on the inner part of metal tray and outer part of the beaker.
D Water droplets are seen on the outer part of beaker only.
Read the given data and select the correct option for the following questions.
Raman carried out an experiment to find out how fast water can pass through four different types of soil. He put each type of soil in four pots with equal sized holes at the base and placed separate dishes at their bottom to collect water. He poured water in them one by one, and used a stopwatch to record the time taken for water to reach the level he had marked same in each dish. His recording is given in the table as shown below.
Which soil is the most suitable for a plant that thrives in wet and clayey soil?