Put a variety of small solid objects into Ziploc bags, and have a member of each group pick-up the bags for each student in the group 3. Ask the students to take out, look at, and touch the objects. Tell the students to try to put their pens through the desk. Tell them to do the same thing with some of the other objects. Together discuss that one cannot go through solids easily.
External force has to be applied.
Discuss and conclude that they do if no force is applied to them. Take ice cubes between your hands. Hold your hands up and ask what is happening. Together discuss the change of phase from a solid to a liquid. Pass out clear plastic glasses half-filled with water.