We all know, Density = Mass/ volume.
When volume increases and the mass remains the same , the density will decrease considerably.
The question is incomplete, here is the complete question:
Silicon reacts with carbon dioxide to form silicon carbide and silicon dioxide. Write the balanced chemical equation.
<u>Answer:</u> The balanced chemical equation is written below.
<u>Explanation:</u>
Every balanced chemical equation follows law of conservation of mass.
A balanced chemical equation is defined as the equation in which total number of individual atoms on the reactant side is equal to the total number of individual atoms on product side.
The balanced chemical equation for the reaction of silicon and carbon dioxide follows:

By Stoichiometry of the reaction:
2 moles of silicon reacts with 1 mole of carbon dioxide gas to produce 1 mole of silicon carbide and 1 mole of silicon dioxide
Hence, the balanced chemical equation is written above.
A. chemical energy into thermal energy
88226Ra→ 86222Rn + 24He is the reaction that describes an alpha emission because radiations are released.
<h3>Describes an alpha emission?</h3>
Alpha radiation occurs when the nucleus of an atom becomes unstable and alpha particles are released in order to restore stability. Alpha decay occurs in elements that have high atomic numbers, such as uranium, radium, and thorium etc.
So we can conclude that 88226Ra→ 86222Rn + 24He is the reaction that describes an alpha emission because radiations are released.
Learn more about radiation here: brainly.com/question/893656
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