Employ observation skills, which are needed in any science experiment with a first day activity. Place pebbles, coins or any small item in a shoe box. Tape the box shut and wrap the box with paper. Have enough boxes available for each three students to have their own observation box. Ask the students in groups of three to determine what is in their box by observing how it performs in the covered container.
Making a hypothesis -- educated guess -- is an important step in the scientific method. Perform a simple experiment asking the students to guess what will happen. Ask the students to predict whether the soda can can be crushed by a bucket of cool water. Heat a small amount of water in a soda can. With tongs, take the can off of the burner and place it in a pan of cool water. The water vapor condenses and the can crushes instantly.
Give a trio of students a group of items to classify. Classification is an important skill in science which involves observing similarities and differences. A selection of different types of rocks, leaves, pictures of animals or even a group of dollar store toys will employ ordering and classifying skills.
Perform some short but amazing demonstrations to help the kids understand science is fun. Make oobleck with corn starch and water. Oobleck presents itself as a solid and a liquid. It will be mind boggling to the students. Drop a boiled egg in a fruit drink bottle. Place a piece of flaming newspaper in the bottle. Set the egg on the mouth of the bottle. it will be sucked into the bottle. The students will know this science class is going to be filled with fun.