Shenzhou-14 taikonauts on China's Tiangong space station on Wednesday wowed students across the mainland with zero-gravity experiments.

Mission commander Chen Dong, along with his crewmates Liu Yang and Cai Xuzhe, were live-streaming to students in Beijing, Shandong, Henan and Yunnan.

It's the third such lecture from the Chinese space station aiming to boost students' knowledge of manned space flights and to encourage young people to develop an interest in science.

The taikonauts floated into the frame one by one at around 3.45pm Beijing time and waved to students when the lecture, the first held in the Wentian module, began.

They gave students a tour of Wentian, during which Liu showed how they sleep in the module.

"Inside Wentian module, our sleeping quarters are actually different from the core module. It's horizontal in the core module, but here, it's in a vertical direction.

"And of course you cannot sleep in this direction on Earth but now we are in micro-gravity, so any direction, we feel the same."

Liu also explained how things in space can move in ways never before imagined on Earth because of the lack of gravity.

She demonstrated this by effortlessly drinking mango juice from an extra-long straw.

"It's a very easy task for me. On Earth, because of gravity... you need to spend a lot of effort if you sip through a long straw. But here, there's no gravity, so with very little effort, I can use this crazy-long straw to drink the juice."

The previous two lectures of the "Tiangong Class" series were delivered by the Shenzhou-13 taikonauts from the station's core Tianhe module over the past year.

Wentian is the first lab component of China's space station, which is still under construction. The module was launched on July 24.