This is one of my favourite Twitter tools that helped me a lot back in the day when I was running our twitter chats. It allows for tracking differnt keywords, users, hashtags, etc. in separate columns, and what I also particularly liked was the ability to schedule tweets, which turned out super helpful during the aforementioned tweet chats.
If you're more into analytics side of things of tracking different keywords, you might want to give https://brand24.com
a go. It will provide you with a number of metrics such as social media reach, number of mentions, or social influence of different authors, so pretty much something you're going to miss with the majority of free tools.