Research some ways in which scientists and engineers have harnessed and currently use the energy in fossil fuels to benefit society. Think about how these methods involve a chemical reaction, and explain how energy is conserved. Describe one method of using fossil fuels for energy, and state one advantage and disadvantage about this method. In your replies to others' comments, state whether you agree or disagree with the advantages and disadvantages they list and explain your reasoning. Hint: Consider what happens to fossil fuels (such as coal, natural gas, and petroleum) when they are burned.

Explanation:

Fossil fuels are fuels that are formed by naturally processes leading to the formation of crude oil, coal and natural gas.

Scientists and engineers have used the energy from these fossil fuels to benefit the society by converting these fuels into consumable products for engines which are used for various daily life routine, such as transport (as in the case of the combustible engines in cars, trains, airplanes and ships), power generation (as in the case of gas turbines for power generation, petroleum or diesel for the engines of power generators) and even for home use in food processing (as in the case of cooking gas).

The chemical reaction mostly involved in this process especially in the case of engines is combustion reaction. Combustion reaction is an exothermic reaction in which an organic substance is burnt in excess oxygen to produce carbon dioxide.  The energy conserved in this reaction (combustion reaction) is from stored potential energy (in the form of chemical energy) to thermal energy (which is the heat released when the hydrocarbon is burnt).

As mentioned earlier, one of the methods of using fossil fuels for energy is it's use in power generation by power generating sets (generators) and gas turbines. One advantage of using fossil fuel products for power generation is that it is cheaper than it's alternatives (such as solar power generation). However, one disadvantage of using fossil fuel products for power generation is that they release toxic gases/chemicals (such as carbon monoxide, CO, nitrogen oxides, NO and NO₂) into the atmosphere.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.