Physics 問題

1. 我地keep warm 係因為air is trapped next to our bodies? 唔係好同意, 唔係主要因為件衫係bad conductor, reduce the heat loss 咩? 唔係做乜愈厚ge 衫愈keep warm?

.........兩個都有d岩。不如睇下我既答案ok?

因為我地著住件衫，而衫與人體之間會有空氣，，而空氣係bad conductor，加上衫既物料都係bad conductor，所以可以keep warm。

2. water 是否room temperature? if yes, why do we feel cooler if we touch it?

It is because specific heat capacity of water is high. So if water want rais temperature,it would have more energy.And room temperature can not do it.so water is colder than room temperature.

3. 一碗hot soup 放係到, 會有好似steam ge 野不停向上, 個D 係唔係水蒸氣due to evaporation?

係，個d係水蒸氣。係，係蒸發。

1)我覺得你

2)唔係, 你用溫度計度話會係一樣...你都知道我地nerves 唔係真係咁accurate gar la. 至於點解會覺得cool D, 首先要解釋點解會覺得冷:

當你伸手落杯水的時候，手熱過水, 於是heat tends to go from hand to water until the temperature is equal. 當rate of heat going from hand to water 快過身體producing heat的情度比快過在air 中, 手就覺得冷了。
當在正常room temperature 我們沒有特別感覺是因為我們大腦has got used to the message from sensory cells about the temperature at a certain degree.

air 同 water 在此問題上有一個決定性分別---air 的 density 係smaller than that of water,於是可以想象到有兩個結果
i)water conducts heat faster than air.

ii)由於水molecules (其實不是真的是molecules...但現在還是這樣理解吧)are more packed together, 每 1kg 水要比1kg 空氣多吸好多energy 先至做到temperature rise by 1degree celcius(Temperature 係指 AVERAGE kinetic energy of atoms 你知架啦) ie.水的specific heat capacity 比air大 (當然 specific heat capacity不只會被density 影響的...這些我不盡述了)

當water molecules 比air molecules帶走 heat 較快,
同時water 所需的熱能去增加溫度較多時
rate of heat going from hand to water is faster than that of air
so we feel cooler

3)係

1. 我地keep warm 係因為air is trapped next to our bodies? 唔係好同意, 唔係主要因為件衫係bad conductor, reduce the heat loss 咩? 唔係做乜愈厚ge 衫愈keep warm?

首先，在explain之前，你要知道heating係點happen。傳熱係靠particles間的碰撞。在solid時，particles間的separation較close，有較多的collision，而gas的時候，particles間的separation較far away，collision相對也較少。因此，solid 傳熱是比gas好，而air比件衫係更keep warm

2. water 是否room temperature? if yes, why do we feel cooler if we touch it?
水在室溫當然係liquid，但水係liquid時並不一定要在室溫的。
而且正常來說，在室溫底下，水的temperature係below room temperature