F.3 Phy問題

[kaka93]

Q1.Why there is steam coming out of the rice cooker before the water boils?
2.A bowl of cold wateris placed on an electrical heating pan.the temperature of water increases from 20度to70度?
Q2.1.Why the temperature rises,explain in terms of molecular energy?
Q2.2.Why we use 'average' energy to explain the above answer?
Q2.3.What is the change in potential energy of water molecular?
Q2.4.What happens to the internal energy of the system?

[efilm]

Q1.Why there is steam coming out of the rice cooker before the water boils?

Evaporation.
水的 molecule 會撞來撞去，有 d molecule 撞撞下時會 gain K.E.，當賺夠 K.E. 時，果 d molecule 就會離開水面，咁果 d 就係你見到的 steam。

2.A bowl of cold water is placed on an electrical heating pan.the temperature of water increases from 20度to70度?

呢條係問題？定只係一句描述？

Q2.1.Why the temperature rises,explain in terms of molecular energy?

因為加熱時 d molecule 愈郁愈快，咁個 avg. K.E. 就升左，咁即係話個 temp. 都升左。

Q2.2.Why we use 'average' energy to explain the above answer?

因為 temp. 係量度 avg . K.E. due to random motion of molecules in the system.

Q2.3.What is the change in potential energy of water molecular?

其實問乜？change of state?

Q2.4.What happens to the internal energy of the system?

升左