When a solid is heated its particles melts and change into liquid
no melting is a physical process
Shifting temperature. If its colder, the harder it will get because the particles will compress together. If its warmer, the substance will liquify (melt) or even turn into gas because the particles move apart from each other.
If gold gets hot enough, it will melt. What type of change is this?
Igneous rocks can change into metamorphic rocks from great heat and pressure as all other rocks can, melt into magma, the molten rock, and erode into sediment, which are rock fragments.
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No, this is a physical change. Although you melt the glass, the molecules are not transformed into another type of molecule.
kinetic energy
The simple act of melting the steel is a physical change. No one melts steel out of boredom. If the melt is so you can add other elements to it, then you've made a chemical change. If you're forming useful products from the steel without changing its chemistry, it's a physical change.
Particles of a liquid: 1) More loosely connected 2) Can collide with each other and most past one another
It depends on what type it is.
ice
A lightsaber. Also a stove, a magnifying glass (used with sunlight), a toaster oven, and practically any other heat source you can think of. Chocolate is easy to melt.