Mystery Box – Bay Area Discovery Museum

Mystery Box

Children will explore mystery substances, make observations, and describe the properties that distinguish the common states of matter—solid, liquid, and gas.

Materials Required

  • 10 shoeboxes
  • Everyday objects/substances to put inside the shoeboxes, including a mix of solids, liquids, and gases (e.g. marbles, bottle of water, balloon, pencil)
  • Paper and pencil


  1. Review or introduce the three most common states of matter—solid, liquid, and gas—and their properties.
  2. Split children into partners and give each pair a shoebox. Have one child close their eyes while the other partner picks an object to put inside a shoebox.
  3. Without opening the shoebox, ask the other child to describe what they observe. What do you predict is inside the shoebox? What can you tell me about the object’s properties? Do you think it is a solid, liquid, or gas – how do you know?
  4. After the child has time to describe and observe, open the shoebox to reveal what’s inside. How did their predictions align with the results? What did they notice about each object? What does that reveal about the object’s state of matter?
  5. Make sure partners get a chance to switch and try both roles.

Additional Tips

Try these add-on activities:

  • Hunt for objects around the classroom and nearby. Talk about their properties and decide together whether they are solids, liquids, or gases.
  • Create a collage of solids, liquids, and gases using images cut from magazines, old books, or the Internet.
  • Try a similar but messier version of this activity by filling balloons with various substances such as water, ice, oil, or rice.

Links to Creativity

In this activity, children are given a mystery to solve. They are tasked with acting as little scientists, forming hypothesis and testing out possible solutions. Although this may sound like a complicated task for a child, research over the past 30 years demonstrates that, starting in infancy, children develop and test intuitive theories about the world around them, much like scientists do (Gopnik, 2012; Gopnik, Schulz, & Schulz, 2007; Gopnik & Wellman, 2012). This activity will allow children to practice their hypothesis testing and causal reasoning skills through a playful learning exercise.

Gopnik, A. (2012). Scientific thinking in young children: Theoretical advances, empirical research, and policy implications. Science, 337, 1623-1627. doi: 10.1126/science.1223416

Gopnik, A., Schulz, L. & Schulz, L. E. (Eds.). (2007). Causal learning: Psychology, philosophy, and computation. New York, NY; Oxford University Press.

Gopnik, A., & Wellman, H. M. (2012). Reconstructing constuctivism: Causal models, Bayesian learning mechanisms, and the theory theory. Psychological Bulletin, 138, 1085-1108. doi: 10.1037/a0028044.


This activity was contributed by the Bay Area Discovery Museum. ©2016 Bay Area Discovery Museum. For more information and resources see

Mystery Box

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