My science class is growing unknown seeds and I’ve been watering it for about 7 weeks (https://i.stack.imgur.com/oHDFO.jpg)
It's what is known locally here as a green fred weed. After all, a rose by any other name would smell as sweet, so there you go, but are you happy?
In any science investigation you set out to solve a puzzle, and since these puzzles involve many steps you first need a log of your observations and clear notes of the steps you took. Do you have that log to hand in? It will constitute much of your grade even if you fail to find the name.
First the seed. Stop right there and describe as accurately as you can, taking notes, an individual seed and whether they all look alike. Dimensions in metric, colour, smoothness, slim or fat, blunt or sharp. Take a photo. Sometimes, all you need is the seed to tell immediately what it is, or definitely what it is not. Use botanical terms as much as you can - seeds fall into many groups besides big and small, find out what these are and decide which group your seed might belong in.
Next describe your potting soil - do a pH test and note in the log the constituent parts, peat, vermiculite, sand and so on. Note the date the seed was sown and how deep you planted it, plus the temperature the pot is living in and the amount of light available (bright, shady and so on). The date the first seedling appeared and describe in as much detail as you can what you see and how it changes over time. If you have more than one come up, tease a single seedling out and wash off the soil so you can describe the root. More photos, constantly take detailed notes. Use a magnifying lens to get detail.
You may not know exactly what you have until it flowers; it is possible that your instructor chose some plant that produces a flower reliably a short time after sowing, in which case you are lucky.