In rural India, children have begun smearing Vaseline on tree leaves. Some coat only one side of the leaf; some coat both sides. Others choose not to put any Vaseline on their leaves at all.
An hour or two later, they return to the tree to see what has happened to their leaves.
"They're looking at the impact on the rate of photosynthesis," said Sai Chandrashekar, chief of operations for educational foundation Agastya. "They have a lot of fun - they're out in the open and enjoying themselves, and also learning.
"If they weren't doing that, they'd be learning from a textbook - very rote-based, mechanical and not hands-on."
The photosynthesis lesson is one of more than 100 offered by Agastya's Lab on a Bike scheme. The project is among 15 shortlisted for the 2015 Wise (World Innovation Summit for Education) Awards. Six of the finalists will receive an award, along with a $20,000 (pound;13,000) prize, at the Wise summit in Qatar in November. The awards recognise and promote projects around the world that have found innovative ways to address educational challenges and make a positive social impact.
This is undoubtedly the goal of the Lab on a Bike programme, in which 59 motorbikes take science experiments out to government schools across eight Indian states.
"We wanted to spark curiosity and nurture confidence in economically disadvantaged children, through hands-on experiential methods," said Ramji Raghavan, the company's chief executive.
Agastya initially launched a number of mobile science vans. "But there are many parts of India that can't be reached by van, because the roads are poor," Mr Raghavan said. "A bike can literally zip in and out of little hamlets and villages, carrying science experiments."
The labs-on-bikes each serve between 15 and 20 schools. Every motorbike carries one or two boxes in its side carriage, a single box containing a variety of experiments suitable for children between the ages of 11 and 16.
For example, one box provides a kit with which to teach optics. It includes a battery-operated light bulb, convex and concave mirrors, lenses and prisms. The experiments include demonstrating that light travels in a straight line and showing children a diverging light ray.
The aim is to stimulate curiosity and encourage children to ask their own questions. In one school, for example, pupils recognised that the rubbish filling their village's streets posed a health risk. So they began educating villagers about the dangers of rotting rubbish and helped them to set up a proper disposal system. Then they petitioned the local municipality to arrange for a rubbish truck to include their village on its rounds.
Teachers are also offered training in how to make the most of the labs-on-bikes, and in how to incorporate experiential lessons into their own teaching. And Agastya offers advice on how teachers can create their own labs using low-cost materials. "Cost is a very critical element in this," Mr Chandrashekar said. "Schools don't have large budgets for this stuff."
Agastya trainers show teachers how to construct an experiment for as little as 20 rupees (20p). The foundation also runs awareness-raising sessions for parents, allowing them to try some of the experiments for themselves. "We teach them the science behind some of the superstitions they may have," Mr Raghavan said.
"A lot of people are frightened of eclipses. Or some quacks come into the village and throw chemicals to the ground and it catches fire. Then people think this guy has some magical power and they must pay him obeisance. So we show them that you just need the right chemicals."
There is another advantage to this. "They see what's happening, they enjoy themselves and they realise what their kids are getting from school," Mr Chandrashekar said. "Therefore they get motivated to send their kids to school, rather than to the farms to work."
The shortlist for the 2015 Wise Awards comprises 15 finalists, including:
- Bridge International Academies A chain of low-cost private schools across Kenya, Uganda, Nigeria and India.
- The Edible Schoolyard A US-based project aiming to transform children's health by integrating food education into subjects across the board.
- Talking Book Programme This Ghanaian project produces practical audio lessons on sustainable farming methods and health practices.
- GirlEng A South African scheme encouraging girls to study engineering.