Final answer:
Changes due to heat include the melting of ice and the combustion in an oxyacetylene torch, which is exothermic, whereas a cold pack represents an endothermic reaction. Changes due to pressure are represented by the irreversible free expansion of gas into a vacuum.
Step-by-step explanation:
An example of a change happening because of heat and/or pressure is the melting of ice. When ice is subjected to heat, it absorbs energy in the form of heat without increasing in temperature until it reaches the melting point. At this point, the ice undergoes a physical change and transitions from a solid to a liquid. This process is an example of a phase change due to heat transfer. Another illustration of a change due to heat is witnessed when we use an oxyacetylene torch. The combustion reaction that occurs is an exothermic process, releasing not only heat but also light. Conversely, when a cold pack is used, it undergoes an endothermic process absorbing heat from the surroundings, which results in a cooling effect. This is another instance of a change due to heat. In terms of pressure-induced changes, the free expansion of a gas into a vacuum is one where the gas can only be returned to its original state if external work is done on it, signifying an irreversible change because the gas itself does no work on the surroundings in this process.