一直都搞不清的物理問題

p445hkk20001

分子由固態變成液態就必然潛熱來克服分子與分子之間的引力(范德華力)
這樣來說 水變冰 應該是吸收能量@@ 除非有咩例外? 冰的密度比水低

-終場ソ使者-

分子是不會由固態變成液態呢!
其實,我也攪不清你的問題是甚麼-.-

[S]Mangoray

固體 密度一般較高
分子間距離近 , 所以之間引力大
液體 分子間距離較固體時遠 , 分子間引力低
將固體變液體,,就要能量去抗衡個吸引力
個能量又稱為潛熱

p445hkk20001

但冰密度比水低

[S]Mangoray

如果冰比水密度高,咁冰極就冇晒魚啦

廢話講完
原因係 ,, 水分子間有氫鍵 ,, 當它以固體形成存在時
6個水分子會走埋一齊,形成一個開放式結構(有較大空間)
所以密度就低d

-終場ソ使者-

Don't you know that?
By considering the case from ice to water.
The vibrations among H₂O molecules are becoming more vigorous,(the distances among H₂O molecules are becoming longer and longer)ie the density becomes smaller!Therefore,latent heat of fusion is absorbed.
Conversely,you can imagine that the case from water to ice does not absorb engergy,it should release energy.
But, what about the van der Waals' forces?
In fact,it doesn't directly reflect the energy released/absorbed.But, you know energy absorbed make distances among molecules become longer, the van der Waals' forces will be broken away.

p445hkk20001

其實我仲有一個問題
火係咪應該有重量 凡有能量的存在 就應該有m
我覺得係有重量@@

-終場ソ使者-

凡有能量的存在 就應該有m

你肯定?
你咁講好有A. Einstein既mass-energy equivalence既feel-.-
ΔE=Δmc²
不過佢係一條由mass轉去energy既定律
eg:
²³⁵U+n→¹¹⁴Ba+⁹⁰Kr+2n
如果你細心咁睇(基本上係睇唔到-.-),你會發現m(R.H.S.)<m(L.H.S.)
Δm轉化既ΔE(c²係一個極大既數字,所以少少mass就可以轉化極多energy)

至於火有冇mass,我就唔知啦,聽人講係有,可信性唔高-.-

p445hkk20001

我覺得呢個係一個好高深既物理問題

[S]Mangoray

火係有重量
得個"知"字就夠