Embibe Experts Solutions for Chapter: Changes Around us, Exercise 1: Exercise

Prasanna and Tamanna went on a family vacation. They saw large trees in the backyards of many houses in many places. When they returned from their tour, they found that their house was devoid of large trees. They made the decision to plant some large trees in their backyard. They brought some saplings for large trees and planted them in their backyard. They watered and cared for the plants on a regular basis. After a few years, their house had three large trees and as a result of these tree's shade the interior of the house remained cool during the hot summers.

Based on the above understanding, answer the following questions:

(a) Is growing of trees a useful change?

(b) Is growing of trees reversible or irreversible?

(c) Is growing of trees a slow chenge or fast?

Manu and Ranbir were childhood friends. Manu invited Ranbir to his birthday party one day. So Ranbir was on his way to Manu's birthday celebrations. He was meeting Manu after a long time, so he left his house early to see him. His vehicle's petrol ran out while he was driving. As a result, he filled the petrol in the petrol bunk and drove to Manu's house. Ranbir hugged and wished Manu when he arrived at his house, and they were delighted to see each other and conversed. Ranbir noticed that Manu had grown taller when he saw him while they were talking. Manu, Ranbir, and their friends went to cut the cake after a while. Manu walked up to a cake that was lit with candles and cut it. Ranbir and his friends then ate cake with Manu and greatly enjoyed it.

From the above understanding, answer the following questions:

1. Whether the Burning of candles on the cake is an example of chemical change or physical change?

2. Manu having grown taller is a reversible change or irreversible change.

One day while travelling to her aunty’s house Navika noticed an old house with a big metallic gate. The gate was completely weared out and is not at all lustorous. It was rather covered with a browny reddish substance.

While she was thinking, she had the following thoughts. Please help her in finding their answers.

a. Why do the articles made of iron when placed in moist air get fully covered with a reddish-brown powdery substance?

b. What is the name of this process?

c. Is this process a chemical or a physical change?

d. Is the process mentioned in 'step b' reversible? Give the reason to support your answer.

It was winter and the school students gathered for assembly on the school's ground. While the assembly was yet to be started, Ramya a class $6$ student started playing with her friends by blowing the smoke-like thing out of their mouths. Seeing them doing this, the lower grade students also started doing the same thing.

One of the class $5$ student Gopal asked one of Ramya's friend that from where this smoke is coming, and why don't they experience such a phenmenon in the summers?

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.