Elasticity: The ability of a material to return to its original shape after being stretched or pulled. Rubber bands have elastic characteristics.
Fluid: Something that takes the shape of its container. Air, water, and oil are all fluids. (For older kids and adults: A state of matter in which the molecules can move past one another; fluids assume the shape of their container.)
For older kids and adults:
Polymer: A compound, like starch, that is made of large molecules with relatively simple repeating units.
Solution: A mixture of two or more substances in which the particles are dispersed evenly throughout. Kool-Aid that is completely dissolved in a pitcher of water is a solution.
Viscoelastic material: A material that behaves like an elastic solid and a viscous liquid, meaning that it can change its shape when pressure is applied but can also flow slowly.