(The title is misleading. Not exactly Napalm, but something similar is created, and acts like Napalm)
In a hypothetical scenario, what if Scientists discovered before 1914, on making an earlier form of Napalm or something similar
Then WWI starts, and like poison gas, Botha sides started using this Napalm.
How could tactics change if earlier-Napalm was created?
Styrene had been isolated by European chemists before 1870, and seems to predate the discovery of Naphthenic acid being a contaminant in some Crude Oil stocks with Kerosene Distilation, and Palmitic acid for Soap making by time of the Crimean War
So all the compounds are there, by 1890, for Napalm 'A' and 'B' formulations
Early aircraft can't carry enough to be really worthwhile, with even the the Gotha and Zeppelin Bombers having access to magnesium metal type incendiaries for the night raids on English cities
Artillery shells don't have much volume, so HE filling is still the best use, since after regular shelling, there just isn't much to burn in the Trench zone
So that leave the ground projectors against strongpoints, like the Germans invented, so the effect is greater in the trenches, but it's not enough to alter the outcome during that conflict very much.
But would probably get added to the banned items the German Military couldn't use