Dissect It

Nothing impresses a kid like brandishing a knife and saying, "Let's cut that open and see what's inside." Here are three household objects that are fun to slice apart. And one you really shouldn't.

Baseball

Is it safe to open? Yup.

Technique: Put it in a vise, then go at it with a hacksaw.

What your kids will learn: That the material inside affects the ball's behavior. Cores used to be made of rubber but were changed to cork in 1910. This made the ball more bouncy, ushering in the "live ball" era that allowed Babe Ruth to become a legend. But home runs shouldn't be too easy, which is why the outer layers consist of yarn, deadening the ball.

Light Stick

Is it safe to open? Sure—if you're smart about it.

Technique: Cut with scissors near the end and pour the liquid into a glass jar. Remove the inner glass vial and put it in another container.

What your kids will learn: That two fluids (typically hydrogen peroxide and phenyl oxalate ester) rearrange themselves into phenol and peroxyacid ester when combined; the chemical reaction gives off energy in the form of light called chemiluminescence.

Battery

Is it safe to open? Absolutely not.

Technique: Find a professional with a lab and a saw.

What your kids will learn: That when the battery is inserted into a flashlight or other device, a circuit connects the positive cathode and negative anode, sparking an electrochemical reaction between them. The anode starts spitting out electrons, which flow through a wire toward the cathode, producing an electric current.

Speaker

Is it safe to open? If it's not hooked up.

Technique: Use a utility knife to slice around the cone.

What your kids will learn: How electricity is turned into sound. When the audio signal courses through the wire coil, the coil turns into an electromagnet that subtly moves the paper cone, pushing air molecules in and out of the speaker. And since all sound is essentially the movement of air, this is how a speaker reproduces the strains of Taylor Swift.