Quote:
Originally Posted by shakeel ghori
Good efforts..
>The second most abundant metal found in earth's crust is silicon. Here is the sequence of 9 elements which account for most of the matter found in earth's crust:
oxygen, silicon, aluminium, iron, calcium, sodium, potassium, magnesium, and hydrogen. out of them the non-metal elements are oxygen and hydrogen.
>Charcoal is made by animals' bones.
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corrected answers :-
1)
Element Abundance Abundance
(percent by weight) (parts per million by weight)
Oxygen
46.1% , 461,000
Silicon
28.2% , 282,000
Aluminum
8.23% , 82,300
Iron
5.63% , 56,300
Calcium
4.15% , 41,500
Sodium
2.36% , 23,600
Magnesium
2.33% , 23,300
Potassium
2.09% , 20,900
Titanium
0.565% , 5,650
Hydrogen
0.14% , 1,400
2)One of the most common forms of carbon is charcoal. Charcoal is made by heating wood in the absence of air so it does not catch fire. Instead, it gives off water vapor, leaving pure carbon.
3)
• Water is the only substance in nature that has lower density on its solid state. This happens because air is trapped in betwen the molecules of water when they freeze and make it expand. This is the reason water is so importat for lifeforms to appear on planets
• The density of water increases until 4 degrees Celsius at which point it starts to decrease. As a result, ice is lighter and will float on water. When ice melts its temperature rises to the 4 degree point and it starts to sink into the surrounding water. Density is connected to state so solids are denser than liquids which are denser than gases.
Density= Mass/Volume. When water freezes, its volume increases. This is why a frozen bottle of water expands to the point of bursting. By the formula, if volume increases and Mass stays the same, then the value of density decreases. Thus, this is why ice floats and is less dense than water. When the ice melts, the reverse happens in that its volume decreases and again by the formula, density will increase.
corrections are most welcome.