das Pulver
powder
A dry substance made up of very fine, small particles.
Löse das Pulver in warmem Wasser auf.
Dissolve the powder in warm water.

powder
Loading your saved state.
powder
A dry substance made up of very fine, small particles.
Löse das Pulver in warmem Wasser auf.
Dissolve the powder in warm water.

The meaning of 'Pulver' (powder) becomes clear from context. In everyday situations (kitchen, medicine, bathroom), it usually refers to the general substance. In connection with weapons, history, or fireworks, it means gunpowder.
Für den Kuchen brauchen wir noch Backpulver.
We still need baking powder for the cake.
The word 'Pulver' (powder) is a common component of compound nouns that describe a substance in powder form. Examples are 'Waschpulver' (washing powder), 'Kakaopulver' (cocoa powder), or 'Proteinpulver' (protein powder).
Gib bitte noch etwas Kakaopulver in die Milch.
Please add a little more cocoa powder to the milk.
When talking about powder that is used in a liquid, the typical verb is 'auflösen' (to dissolve). A common phrase is also 'in Pulverform' (in powder form).
Dieses Medikament gibt es in Tablettenform und in Pulverform.
This medication is available in tablet form and in powder form.
The idiom 'sein Pulver verschossen haben' (to have shot one's bolt) is fixed. The possessive pronoun ('sein') changes to match the person who has no arguments or energy left.
Ich kann nicht mehr diskutieren, ich habe mein Pulver für heute verschossen.
I can't discuss this anymore; I've shot my bolt for today.
dust
'der Staub' and 'das Pulver' are both made up of very small, dry particles. 'Staub' usually means dirt or fine particles that lie on furniture or float in the air. 'Pulver' is more often a specific dry substance that you use, for example 'Waschpulver' (washing powder), 'Kakaopulver' (cocoa powder), or 'Medizinpulver' (medicine powder). The words can be confused because both are fine and dry. The practical difference is: Staub is often something you wipe away; Pulver is usually something you use intentionally.

Mila rührt das Pulver in ein Glas Wasser.
Mila stirs the powder into a glass of water.
Auf dem Regal liegt so viel Staub, dass ich es heute putzen muss.
There is so much dust on the shelf that I have to clean it today.