2H2 + O2 + 2H2O In this chemical equation, there are two Hz molecules and
Oz molecule
present in the reactants (the
_). The arrow represents the reaction
occurring. After the reaction, two water
are produced
It is important to point out that during a chemical reaction, the amount of an element
present in the reactants will be
to the amount in the products.
For example, if you start with two oxygen atoms, you will end with
oxygen
atoms. Similarly, if you start w 4g of hydrogen, you will
4g of
hydrogen. The total mass of materials
the total mass of products.
This is known as the Law of
of
During
a reaction, matter can neither be
nor
only
changed in form.
Broken
Equations
left
Chemicals
equal
matter
produced
Conservation
equals
mixtures
produce
created
formed
molecules
reactions
destroyed
ingredients
new
reacting
one
two

Mantle convection  is the slow  creepingmotion of earth's solid silicate  mantle  caused by  convection  currents carrying  heat from the interior  to the planet's surface.[1][2]  the earth's surface  lithosphere, which rides atop the  asthenosphere  (the two components of the  upper mantle), is divided into a number of  plates  that are continuously being created and consumed at their opposite  plate boundaries. accretion occurs as mantle is added to the growing edges of a plate, associated with  seafloor spreading. this hot added material cools down by  conduction  and  convection  of heat. at the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of  subduction  usually at an  ocean trench.[3]this subducted material sinks through the earth's interior. some subducted material appears to reach the lower mantle,[4]  while in other regions, this material is impeded from sinking further, possibly due to a phase transition from  spinel  to  silicate perovskiteand  magnesiowustite, an  endothermic reaction.[5]the subducted oceanic crust triggers  volcanism, although the basic mechanisms are varied. volcanism may occur due to processes that add buoyancy to partially melted mantle causing an upward flow due to a decrease in density of the partial melt.secondary forms of convection that may result in surface volcanism are postulated to occur as a consequence of intraplate extension[6]  and  mantle plumes.[7]it is because the mantle can convect that the  tectonic plates  are able to move around the earth's surface.[8]mantle convection seems to have been much more active during the  hadean  period, resulting in gravitational sorting of heavier molten  iron, and  nickel  elements and  sulphides  in the core, and lighter  silicate minerals  in the  mantle.

B. absorbs violet lightto get absorb sunlight for photosyntesis