Here is a novel presentation idea using a concept of thermodynamics: entropy. The definition from simple Wikipedia is this:
A law of physics says that it takes work to make the entropy of an object or system smaller; without work, entropy can never become smaller – you could say that everything slowly goes to disorder (higher entropy).
We are not going too complicated here, the main catchphrase is “Things in the universe go from order to chaos. This is irreversible.” We will pick up this catch line in the presentation.
Get a pair of spirit slates (with flap), chalk, and double blank cards. If you can get of the pocket versions, the better. This trick is ideal for close-up performance. On the cards, write the letters of the alphabet. Prepare the slate and write a 4-letter word without repeating letters on it. Cover it with the flap.
[Note: there is a useful website for magicians/mentalists where you will find tons of possible solutions: https://www.morewords.com/unique-letters]
The deck is in alphabetical order at the beginning. The four force cards on the top in readiness for the force.
First, introduce the concept of entropy with a few (!) words so everybody understands what it is about. Be sure to mention the “from order to chaos” thing.
Show the slates from both sides and write the Ludwig Boltzmann formula (google about the topic) on the flap. State that this formula represents the concept of order to the chaos which rules the universe. This is not quite correct, but nobody will follow it, anyway.
Then state that thermodynamics says that this process is irreversible (which it is). State that only a magician could prove the opposite.
Put the slates together, place the rubber bands around it and give it a spectator for safe-keeping.
Show the deck in alphabetical order (no one will notice the four displaced cards, especially if your force word starts in the last half of the alphabet. False shuffle the deck, talking about putting the deck into the state of its natural state: from order to chaos.
You must now force the four-letter cards which match the force word. These forces should not disturb the full deck order. A riffle force comes to mind.
Four spectators can be involved in this trick. Each now has a letter card. Have them turn the cards face-up. Ask them to form a word with them, if possible (of course, it is possible).
Then reveal that indeed you were able to put the chaos of the four letters into an order on the slate. Open the slates and show them the word appeared. Lap the flap and leave the slates on the table.
For a final kicker, spread the deck and show them the letter cards arranges back to the order (except the four chosen ones).
A nice presentation, an interesting topic, and a smooth routine that is not difficult to do and leaves you clean.
There you have it.