Take any First Questions and Answers book, such as Time Life for Children's "Why Do Balls Bounce?" and as you read through the questions, demonstrate them. This takes it right off the page and into an instant lesson. Time Life's How Things Work book answers simple questions like why does toast pop up? How does water come out of the faucet? How can I hear my friend on the telephone? How do pens write? How do toilets flush? How do light bulbs make light? etc. Demonstrate these things with simple experiments as you go along and you'll literally watch their minds capturing the concrete value to what they are learning.
My kids loved spending a day doing experiments based on each page. It made for a great learn and discover day!
Telephone string cups really work!