In preparing a foundation upon which to build science skills, we must first ask ourselves "what is exactly is science." Science is so much more than the simple collection of facts. Science is about observation. Yes, we need to know basic facts such as the boiling point for water and that the earth is the third planet from the sun, but we also need to remember that those facts were first discovered by observation.
Young children love memorizing facts and so teaching them science facts such as the order of the planets, would be both fun and useful. But I encourage you to do more than that. Teach them observation skills.
There are four parts to observation:
Ask what is happening.
Predict what might happen.
Test your prediction.
Make sense of the results.
Science involves trial and error, it is a way of thinking. Children learn science best if they are encouraged to investigate and experiment. Young children love to see, to touch, to manipulate. They like to how things change.
When babies throw their plate off the highchair and onto the floor, they are not being bad, they are observing. They wonder what will happen if the plate goes over the edge. They may even be making a prediction. They test the prediction and then try to makes sense of the results. You might say that the are testing the theory of gravity. (Someone else may say that they are testing your patience)
In cooking, let children observe how the butter melts, how the texture of the bread dough is different from the finished loaf, or how vinegar curdles milk. Ask her why she thinks these things happen.
Take walks outdoors and observe the night sky. How does it change from day to night? From night to night? From season to season? Ask why he thinks these changes take place.
And none of this costs a penny.