Topic : Particulate Nature of Matter, Diffusion

The MCQ Section. I would just like you to remember some important concept of the above topic (a) relative molecular mass a property of a gas that affects the rate at which the gas diffuse (b) Melting pts of pure and mixture of metals (alloy). The melting pt of the alloy (eg lead + tin) is always lower than the highest MP metal, in this eg it is lead; not both. (c) how the smell of a gas spread - diffusion

Many MCQ questions can be set just on relative molecular mass. But how it is set, always remember the key properties of gas, liquid, solid. Just ask you a simple MCQ question. Which of these 4 gases is the lightest? N2, O2, NH3, SO2. You must remember relative molecular mass. What's your answer? I can ask you from another way.
Which of the 4 containers containing the above gas each when the lids are open will be filled with air first? A(N2) B(O2) C(NH3) D(SO2)?

When water freezes to solid, what happen?
When ice melt to liquid, what happen?
When liquid evaporates, what happen?

Pls comment.