The plants in large and dense forests in low-lying wetlands got buried under the soil due to natural processes like floods and earthquakes. As more soil was deposited over them, the organic matter was compressed. As the organic matter sank deeper and deeper, these dead plants slowly get converted to coal under high pressure and high temperature. Since coal was formed from the remains of vegetation, it is also called fossil fuel.

(a) Can we turn coal back into the trees?

(b) Is formation of coal from the plants and trees, a fast change or a slow change?

Vasu, a ten-year-old was fascinated as two sparrows seemingly fought and screamed at each other outside the window of their house. Soon he noticed that a big sparrow them bringing grass, hay, etc. and built a small nest on the shrub outside. Within a few days, there were four small eggs in the nest and a few days later four noisy chicks were being fed non-stop by their parents to appease their voracious appetite. Eventually, the young sparrows left their nest one by one. Young Vasu had learnt an invaluable lesson about life.

a) What change did he notice slow or fast? Is it reversible?

b) What invaluable lesson did Vasu learn from this incident?

Ritesh was once out wandering with his younger brother Prajnesh close to a railway track. Prajnesh noticed that there were several gaps in the track. Prajnesh exclaimed that the track was broken right away. Being a science student, Ritesh properly explained these facts to Prajnesh and assured him that there was no problem.

Answer the following based on the above information.

a) Why are gaps left in between the rail joints on the railway tracks?

b) What are the values displayed by Ritesh?

c) Write one example that uses the above principle?

After the Diwali festivities, Meera collected used diyas and wax of burned candles. She melted the wax in a pan and poured it into the diyas. She put a thread in the middle of diyas. When the wax cooled down, it set into beautiful candle diyas. She showed them to her parents and friends and was appreciated for her idea. Based on the information answer the following questions:
a) Which property of wax helped Meera to make such candle diyas?

b) Name any four reversible changes that help in your life.