Answer : The excess reactant in the combustion of methane in opem atmosphere is 
molecule.
Solution : Given,
Mass of methane = 23 g
Molar mass of methane = 16.04 g/mole
The Net balanced chemical reaction for combustion of methane is,
First we have to calculate the moles of methane.
= 
= 1.434 moles
From the above chemical reaction, we conclude that
1 mole of methane react with the 2 moles of oxygen
and 1.434 moles of methane react to give 
moles of oxygen
The Moles of oxygen = 2.868 moles
Now we conclude that the moles of oxygen are more than the moles of methane.
Therefore, the excess reactant in the combustion of methane in open atmosphere is molecule.
The correct answer is C) A substance changes color when heated, but changes back when cooled. Hope this helps.
Answer:
See Explanation
Explanation:
The way by which a metal is obtained from its ore is determined by the chemical reactivity of the metal.
Metals that are highly reactive are chiefly obtained by electrolysis of the metal salt. These metals are found high up in the metal activity series.
Metals that are at the middle of the series are moderately reactive and are obtained by electrolysis or by reduction since they still form ionic salts.
Metals that are far lower in the series can only be obtained by heating them in air because they are mostly unreactive.
Hence, moderately reactive metals at the middle of the series are not obtained by roasting in air.
The term which is used is homogeneous.
when sugar is completely dissolved in the water, the mixture or solution homogeneous, both in same phase and same uniform texture that is liquid.
There two types of mixtures are heterogeneous and homogeneous in different phases.
If sugar is not completely dissolved in water and you see the crystals of sugar in water, then the solution will be heterogeneous.
Answer:
the greenhouse effect occurs in the earths atmosphere
