Hello!
You have asked an excellent question. This is a question that pertains to professional scientists as well, so I'm very glad that you've asked it! My teammates have done an excellent job of answering your question, but I wanted to add my perspective, even if a little repetitive, just so that you can have many different resources available to you when you write up your experiment.
The fact that you made a discovery outside of the hypothesis is great!! You can include this in your write-up, and mention it in the conclusion section of your project when you describe the data and evidence you collected and how you analyzed it. Be sure to focus on your original hypothesis in the conclusion also, though.
There are many different scenarios as to obtaining surprising data, and the one I've described above seems like it would fit your project, but I'll include a few others as well.
Data that supports a NULL HYPOTHESIS is another type of conclusion altogether. This means that when you've analyzed your results, you find that your data supports the exact opposite of what you had originally predicted. This is OKAY!! It's actually great, because science experiments are not about proving the hypothesis to be correct, rather they're about broadening the scope of knowledge that you have about a particular subject, and finding correlations or relationships between variables. When you find that your data supports the Null-Hypothesis (opposite of what you originally predicted), you should not change your hypothesis, but your conclusion should talk about your findings and the opposite effect it had.
Very often in science projects or science in general, there's a large focus on being "right", or "proving" something. When you can understand that science is all about discovery and observation and gathering data to broaden knowledge and it's not at all about "proving" anything, that is when you truly become a real-life scientist
I think that by reading our answers to your question, you'll come to understand this, and there you have it; a real scientist!! It's your duty to apply this knowledge to your project and spread the word to as many people as possible; science is discovery, not being right.
I'm very happy that you asked this question, and it's a question I could spend hours discussing, but for now, this is the end of my answer. I truly hope that was helpful, and if you have any more questions, please post again and we'll be happy to help!!
Good luck with your project!
Stay nerdy,
lmp1341