Novice needs help to help son

[NoviceDad]

Hello. this is my first time posting on this forum. let me start by saying that I am a total novice. I am trying to help out my 7 year old son.

he has a "treasure chest" where he keeps his "treasures" some old coins and trinkets from family trips. well, he wants to add an alarm to the chest, that will alert him if someone opens it. I think it is great that he wants to dabble in electronics. so, I want to help him however I can. He needs something to know when the circuit is broken to trigger a buzzer.
he has a battery pack (3 x AA) and a small 1.5-3v buzzer from an old toy that he wants to use for the alarm. he got a small circuit board and some wire from a trip to Radio Shack with his mother. I have an old soldering iron from my dad and can help him solder. We have a RadioShack not too far away, so we can get whatever parts are required.

so, now I need to know what kind of circuit he needs to create. I have searched the internet over the past few nights but can't seem to find anything simple enough for a 7 year old and his novice dad to understand.

I hope to help him succeed in hopes it might spur on an interest in electronics.

so, if anyone can point me somewhere or give me some Electronics for Dummies help, it would be greatly appreciated.

Thanks in advance for any help!

Jim

[b.r.sitaram]

There are many circuits available online that use an LDR (light dependent resistor) to sound an alarm. The basic principle is that when light falls on an LDR (e.g. as a result of a lid of a box being opened), its resistance drops, which sounds an alarm. The circuits are simple. Since your son is so young, you can consider using solderless breadboards or prototype boards for making the circuit, rather than using PCBs and soldering it.
Please let me know if you are interested in more details.