Why a kettle lid moves

水开时，壶盖轻轻动起来。

shuǐ kāi shí， hú gài qīng qīng dòng qǐ lai。

When the water boils, the kettle lid begins to move gently.

热水产生的蒸汽向上升。

rè shuǐ chǎn shēng de zhēng qì xiàng shàng shēng。

Steam produced by hot water rises.

蒸汽能够推动较轻的壶盖。

zhēng qì néng gòu tuī dòng jiào qīng de hú gài。

Steam can push a light kettle lid.

小华把自己的问题写在本子上。

xiǎo huá bǎ zì jǐ de wèn tí xiě zài běn zi shàng。

Xiaohua writes his question in his notebook.

奶奶用水受热来解释这个现象。

nǎi nai yòng shuǐ shòu rè lái jiě shì zhè ge xiàn xiàng。

Grandma explains the phenomenon by describing what happens when water is heated.

我们要用观察到的现象寻找证据。

wǒ men yào yòng guān chá dào de xiàn xiàng xún zhǎo zhèng jù。

We should look for evidence in what we observe.

厨房里，奶奶正在烧水，小华站在安全的地方等她。

chú fáng lǐ， nǎi nai zhèng zài shāo shuǐ， xiǎo huá zhàn zài ān quán de dì fang děng tā。

Grandma is boiling water in the kitchen while Xiaohua waits at a safe distance.

水快开的时候，壶盖轻轻动了几下，他觉得很奇怪。

shuǐ kuài kāi de shí hou， hú gài qīng qīng dòng le jǐ xià， tā jué de hěn qí guài。

As the water nears boiling, the lid moves slightly, surprising him.

小华问：“没有人碰它，壶盖为什么会动呢？”

xiǎo huá wèn：“méi yǒu rén pèng tā， hú gài wèi shén me huì dòng ne？”

He asks, “Why does the lid move when nobody touches it?”

奶奶先提醒他不要靠近热水，再解释水受热会产生水汽。

nǎi nai xiān tí xǐng tā bú yào kào jìn rè shuǐ， zài jiě shì shuǐ shòu rè huì chǎn shēng shuǐ qì。

Grandma first tells him to stay away from the hot water, then explains that heating water produces water vapour.

壶里的水汽压力增大，能把比较轻的壶盖往上推。

hú lǐ de shuǐ qì yā lì zēng dà， néng bǎ bǐ jiào qīng de hú gài wǎng shàng tuī。

Increasing vapour pressure inside the kettle can push a light lid upwards.

小华画了一个壶，用箭头表示向上的推动，并把问题写在旁边。

xiǎo huá huà le yí ge hú， yòng jiàn tóu biǎo shì xiàng shàng de tuī dòng， bìng bǎ wèn tí xiě zài páng biān。

Xiaohua draws a kettle and arrows showing the upward push, writing his question beside it.

奶奶说，提出问题是学习的开始，还要用观察和可靠的解释寻找答案。

nǎi nai shuō， tí chū wèn tí shì xué xí de kāi shǐ， hái yào yòng guān chá hé kě kào de jiě shì xún zhǎo dá àn。

Grandma says questions begin learning, followed by observation and reliable explanations.

A 壶盖为什么会自己动？

hú gài wèi shén me huì zì jǐ dòng？

Why does the lid move by itself?

B 壶里的水汽会推动它。

hú lǐ de shuǐ qì huì tuī dòng tā。

Water vapour in the kettle pushes it.

A 我能走近一点看吗？

wǒ néng zǒu jìn yì diǎn kàn ma？

Can I go closer to look?

B 不要靠近，热水和蒸汽会烫伤人。

bú yào kào jìn， rè shuǐ hé zhēng qì huì tàng shāng rén。

Stay back; hot water and steam can scald.

A 那我怎样记录这个发现？

nà wǒ zěn yàng jì lù zhè ge fā xiàn？

Then how can I record this discovery?

B 画图和箭头，再写出问题和解释。

huà tú hé jiàn tóu， zài xiě chū wèn tí hé jiě shì。

Use a drawing and arrows, and write the question and explanation.