To first answer this question, we must define what science fiction means. Merriam-Webster dictionary defines science fiction as "fiction dealing principally with the impact of actual or imagined science on society or individuals or having a scientific factor as an essential orienting component." The Gunn Center for Science Fiction at the University of Kansas defines science fiction as "the literature of the human species encountering change, whether it arrives via scientific discoveries, technological innovations, natural events, or societal shifts."
When looking at Catching Fire, the second book in the Hunger Games series, we must look for the impact of actual or imagined science on the individuals in the book. We must also look at the societal shifts through scientific discoveries.
The impact of imagined science takes place through the annual Hunger Games. The Hunger Games itself has societal shifts. The introduction of the Hunger Games changed how the citizens of Panem live. You are more likely to be chosen for the Hunger Games if you are poor and have to take free food from the district because you are entered into the Hunger Games each time you take food.
In Catching Fire, we see science fiction take place during the 75th Hunger Games. During the Hunger Games, we see many different types of technological innovations that play a role. For example, we see fog that can move in a certain area that can cause participants to be paralyzed or die. Additionally, there is water that has healing powers. These are just some examples of science fiction in Catching Fire.