How do you do predictions in a science project?

Answer 1

To make a prediction. You have to have an idea of what causality is. A ball drops, will it bounce?

For science, you need to have a good basic understanding of what you're trying to investigate. An example would be knowing that light travels in straight lines, and then doing an experiment with refraction to see the properties of light in different mediums.

What will acid do to a metal? Well you know it's going to eat away at it. You design an experiment where you take some rainwater and put a penny in it. You record your observations, make some data tables, graphs, look at your results.....how long did it take for acid rain to start eating away at the penny? What was the mass of the penny before and after the experiment?

You predict it will lose mass, you predict that if the acidity is concentrated, the penny will be eaten fast. You take another acid like diluted sulfuric acid, knowing the concentration and compare it with rainwater to see the relative concentrations.

These are all predictions.