We evaluate the change in social media postings of Super Bowl 2015 on three social media platforms (Twitter, Instagram and Tumblr) for three categories (commercials, musicals and game) during three phrases (Pre, During, and Post). We perform statistical analysis on more than 3,000,000, 800,000 and 50,000 social media posts from Twitter, Instagram and Tumblr, respectively, identifying significant differences among categories. We identify the predominant category of conversations across the three social networks in phases. Findings show the volume of posts in the During phase is surprisingly less than the Pre and Post phases; however, the hourly mean in the During phase is considerably higher than that in other two phases. We then explore the significance of phase-wide change in second screen conversations across the Super Bowl categories for all three social media platforms. We identify the game category is prominent in Twitter, and Instagram for all phases, but not Tumblr. There are dominant peaks for musicals and/or commercials relative to game in all three phases. No category is predominant on Twitter in During phase. These results are important in identifying the interplay of technology has on social interactions for information sharing via second screen especially across disparate social platforms.