There are some ways to make this project a little more challenging for those who are actually doing it.

1.  First, a couple of the bags of materials can be altered a bit, causing participants to question their discoveries.  For example, one bag can have a larger light bulb in it, therefore, the bulb will not be able to light because it is too many watts.  Another example is to put no wire in one of the bags, but to include twist ties.  This will maybe spark the discovery that if twist ties are stripped, the wire then becomes a conductor for electricity.

Some possible questions to these alterations might be:

Why did my bulb not light?
The bulb in your bag was too big for the battery to handle.  There was not enough energy being conducted, therefore, the bulb was unable to be lit.

How can my bulb light if I have no wire?
Are there any items in your bag that look like they can be used instead of the wire?  (Go through the materials, and try to focus on the twist ties in their bags, and see if they realize the twist ties can be stripped.)

2.  Another alteration would be to not have some of the materials in the bag at all.  Perhaps a bag is missing a bulb, or a battery.  In this case, the group would not realize what they were supposed to do unless they got up and went to other groups to see their discoveries.  Some groups will reach a discovery right away, and others will just try and give up if it is not apparent quickly.

3.  Another question to ask each group is:
How many groups split their materials into two piles?
Some groups will raise their hands and see right away that the materials in the bags can be sorted into conductors and nonconductors.  For those groups who were not aware of this, explain the differences between the two and have a group explain to the others why this was helpful in this discovery process.

4.  A final way to make this a bit more challenging, is to have the participants graph or display the results of this sorting activity and communicate results to others.  Have them discuss any surprises they may have discovered, anything they tried that they thought would work but didn't, and even how they worked together as a group.