Study the given figure carefully. What will happen to the water level in the tub when some air is sucked out of the glass?
When the air is sucked out of the glass, the water will enter into the glass and thus, the level of water in the tub will go down.
Fossil fuels formed over a long period of time when heat and pressure were applied to
Fossil fuels are the most important sources of energy for human beings. Coal and petroleum are kinds of sedimentary rock fossil fuels formed from the remains of plants and animals that lived million of years ago.
Which of these is the most accurate description of air, based on the pie-chart?
Air is a mixture of gases. About 78% is nitrogen, 21% is oxygen and the remaining 1% is mainly argon and carbon dioxide. Air also contains varying amounts of water vapour, dust particles and smoke.
Select the option that groups rocks of two different kinds as shown in the box.
Sandstone : Pumice
The relationship in the box pairs a sedimentary rock (sandstone) and an igneous rock (pumice) together. Similarly, conglomerate is a sedimentary rock and obsidian is an igneous rock.
Select the correct statement out of the following.
Clayey soil holds large amounts of water. On drying, this water escapes and cracks develop. These cracks break plant roots making clayey soil not suitable for plant growth.
Beena performed an experiment in which she took four beakers containing different amounts of water at different temperatures. She added equal amount of salt into each beaker.
Identify the beaker in which salt takes the shortest time to dissolve.
Rate of dissolution of solute increases with increase in temperature and quantity of solvent. Beaker 4 has both, more amount of water and higher temperature which help in fast dissolution of salt in water.
Take a glass and fill it with water up to the brim. Make sure that there are no air bubbles. Take a thick, stiff piece of cardboard and put it over the glass. Place your hand over the card and quickly turn the glass upside down. Now slowly remove your hand.
Q. What does this experiment show?
When you will remove your hand, you will find that the card stays in place and the water does not flow out. This is because air exerts pressure on the card from below to keep the card in place. Here, the pressure exerted by air upwards is more than the pressure exerted by water downwards.
Monty fully filled a glass bottle with water, put a stopper on it and placed it upright in the freezer overnight. When he looked at it in the morning, the stopper was out of the bottle and a column of ice had emerged through the opening of the bottle.
Q. Which one of the following is the best explanation for what Monty had observed?
Water expands (increase in volume) upon freezing. This is due to the fact that upon freezing, water molecules crystallize into an open hexagonal lattice form in which molecules enclose more space among themselves than in the liquid state. Thus, in the given case, volume of water increased when the water froze, forcing the stopper out of the bottle and forming the column of ice.
The U-tube shown below is immersed in ice water. X and Y are the red ink droplets present inside the tube.
Q. What will you observe after some time?
Due to the cooling effect of ice water, the air in the U-tube contracts, due to which the red ink X and Y move downwards.
The graph below shows the temperature of a beaker of water as it is subjected to various treatments.
Q. What could have taken place at point Q?
At point Q, there occurs a gradual decrease in temperature of water, which could have been possible due to addition of ice cubes into the beaker of water.