Complete the sentences to describe nuclear fusion:

• Nuclear fusion occurs when two light atomic ___________ merge together to form a heavier product nucleus.
• The total mass of the resulting nucleus is ___________ than the combined mass of the original reactant nuclei because some mass is converted into energy.

To initiate fusion reactions, gas must be heated to extremely high temperatures to overcome electrostatic repulsion. Calculate the energy required to raise the temperature of 7.5 g of deuterium gas by $80000000{}^{\circ }C$.

• Specific heat capacity of deuterium gas = $4800{J/kg}^{\circ }C$.

Give your answer in scientific notation.

Before constructing full-scale commercial nuclear fusion reactors, researchers rely on computer simulations and small-scale prototype testbeds. Suggest two reasons why testing these models is important.

A major advantage of nuclear fusion over traditional fossil-fuel-based power generation is the absence of greenhouse gas emissions during operation. Explain one environmental consequence of the gases released by combustion of fossil fuels in traditional power stations.