How can I make difference to the world using science?

You could invint something heroic like a light bulb

You can do great things, or little things, after all its the small things in life that matter. You could plan a mission to Mars, or make a better designed sink design, and it depends on the math your doing, if your doing Chemistry you could make new bombs, or make a new type of sugar. You can make a difference with science in a lot of ways.