點解mixing qxygen and nitrogen gas係physical既??

（答案不太肯定，如有錯，還請更改）我認為是不可能有chemical change, 因為nitrogen gas is an unreactive gas.空氣中本身已經有oxygen同nitrogen,佢地都已經mix左，但都無產生任何變化。所以淨係mixing也不可能有physical change。如果將佢地冰凍到變成液態或固態比較合理,佢地淨係變做液態或固態，沒有新嘅物質產生，咁就係physical change啦。
(Physical change is a change in which new substance is not formed. It only change from one state to another state.)

Chemical change is defined as a change where new substances are formed. In a physical change, however, NO NEW SUBSTANCES are formed.

If you mix oxygen and nitrogen gas, then as nitrogen gas is chemically inert, there will be no reaction and NO NEW SUBSTANCES are formed. So it is a physcial change.

希望回答可以幫到你！你有問題，隨時send e-mail俾我啦！