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22. Two properties of friction:
⇒It always acts in the direction opposite to the direction of motion
⇒It depends on the normal reaction between the two surfaces under consideration and also on the nature of the surfaces.
23.Music is the pleasant sound that comes from musical instruments etc. Eg. Sitar, Violin. Noise is the unpleasant sound which doesn't bring a soothing feeling to the ears. Eg. Car horn etc. Yes, Music can become noise at times when it played for a long time at a high volume.
24.A flash of light in the sky caused by an electrical discharge between clouds or between a cloud and the Earth's surface is called as lightning.
( If needed more-The formation of clouds involves friction between water droplets in the atmosphere. The friction charges the particles in the atmosphere. By a process, not yet completely understood, among the positive and negative charges, the negative charges accumulate at the bottom of the cloud and the positive charges at the top. As the accumulation of the charges increases, the cloud will induce positive charges on the ground nearby. As the amount of charge increases, the negative charges on the cloud tend to make a path towards the ground, and it results in a narrow streak of electrical discharge, which we call lightning.)
26.An easily recognized group of stars that appear to be located close together in the sky and that form a picture if lines connecting them are imagined is a constellation. Eg. Big dipper, Ursa Major, Sagittarius...
27.Yeast makes dough rise by reacting with the flour to produce carbon-dioxide. It is this gas that expands the dough.
28. (I DON'T KNOW)
31.There are many harmful effects of noise pollution. They are as follows. (i) Noise pollution can cause temporary or permanent deafening. (ii) Noise pollution can cause many health related problems like headache, high blood pressure etc. (iii) It can cause mental illness due to lack of sleep.
32 .Burning of fossil fuels such as coal and diesel releases a variety of pollutants such as sulphur dioxide and nitrogen dioxide into the atmosphere. These pollutants react with water vapours present in the atmosphere to form sulphuric acid and nitric acid respectively. These acids come down with the rain, thereby resulting in acid rain. Effects of acid rain:
Acid rains damage crops.
Acid rains corrode buildings and structures especially those made of marble such as Taj Mahal.
35.Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Iron displaces copper from its salt solution as Iron is a higher reactive metal than copper.
36.BASIS FOR COMPARISON METALS and NON-METALS
Meaning:Metals refers to the natural elements that are hard, shiny, opaque and dense.Non-metals implies those chemical substances that are soft, non-shiny, transparent and brittle.
Appearance :Lustrous ,Non-lustrous
Hardness:Most metals are hard, except sodium.Most non-metals are soft, except diamond.
Malleability: Malleable ,Non-malleable
Ductility:Ductile, Non-ductile
Sonorous:Sonorous ,Non-sonorous
Conduction:Good conductor of heat and electricity ,Poor conductor of heat and electricity (After the comma it is about non metals)
SOURCE: THE INTERNET
HOPE U FOUND IT HELPFUL! :)
22. Two properties of friction:
⇒It always acts in the direction opposite to the direction of motion
⇒It depends on the normal reaction between the two surfaces under consideration and also on the nature of the surfaces.
23.Music is the pleasant sound that comes from musical instruments etc. Eg. Sitar, Violin. Noise is the unpleasant sound which doesn't bring a soothing feeling to the ears. Eg. Car horn etc. Yes, Music can become noise at times when it played for a long time at a high volume.
24.A flash of light in the sky caused by an electrical discharge between clouds or between a cloud and the Earth's surface is called as lightning.
( If needed more-The formation of clouds involves friction between water droplets in the atmosphere. The friction charges the particles in the atmosphere. By a process, not yet completely understood, among the positive and negative charges, the negative charges accumulate at the bottom of the cloud and the positive charges at the top. As the accumulation of the charges increases, the cloud will induce positive charges on the ground nearby. As the amount of charge increases, the negative charges on the cloud tend to make a path towards the ground, and it results in a narrow streak of electrical discharge, which we call lightning.)
26.An easily recognized group of stars that appear to be located close together in the sky and that form a picture if lines connecting them are imagined is a constellation. Eg. Big dipper, Ursa Major, Sagittarius...
27.Yeast makes dough rise by reacting with the flour to produce carbon-dioxide. It is this gas that expands the dough.
28. (I DON'T KNOW)
31.There are many harmful effects of noise pollution. They are as follows. (i) Noise pollution can cause temporary or permanent deafening. (ii) Noise pollution can cause many health related problems like headache, high blood pressure etc. (iii) It can cause mental illness due to lack of sleep.
32 .Burning of fossil fuels such as coal and diesel releases a variety of pollutants such as sulphur dioxide and nitrogen dioxide into the atmosphere. These pollutants react with water vapours present in the atmosphere to form sulphuric acid and nitric acid respectively. These acids come down with the rain, thereby resulting in acid rain. Effects of acid rain:
Acid rains damage crops.
Acid rains corrode buildings and structures especially those made of marble such as Taj Mahal.
35.Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Iron displaces copper from its salt solution as Iron is a higher reactive metal than copper.
36.BASIS FOR COMPARISON METALS and NON-METALS
Meaning:Metals refers to the natural elements that are hard, shiny, opaque and dense.Non-metals implies those chemical substances that are soft, non-shiny, transparent and brittle.
Appearance :Lustrous ,Non-lustrous
Hardness:Most metals are hard, except sodium.Most non-metals are soft, except diamond.
Malleability: Malleable ,Non-malleable
Ductility:Ductile, Non-ductile
Sonorous:Sonorous ,Non-sonorous
Conduction:Good conductor of heat and electricity ,Poor conductor of heat and electricity (After the comma it is about non metals)
SOURCE: THE INTERNET
HOPE U FOUND IT HELPFUL! :)
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