GSEB Class 6 Science Solutions Chapter 6 આપણી આસપાસ થતાં ફેરફારો

Textbook Exercise Questions And Answers

Question 1. When you walk in a water-filled area, you shorten the length of your clothes by folding or pulling them. Can this change be reversed?
Answer: Yes, this **alteration** **is a revertible process**. Because: by **straightening** the **bent** clothes, they can be **returned** to their **initial condition**.
In simple words: When you fold your clothes to make them shorter, you can always unfold them to make them long again. So, it's a change that can be undone.

Exam Tip: Changes that can be undone or brought back to their original state are called reversible changes. Always remember to state whether a change is reversible or irreversible and provide a clear reason.

Question 2. Your favorite toy accidentally slips from your hand and breaks. You never wanted such a change to happen. Can this change be reversed?
Answer: No, this **alteration** **is not a revertible process**. Because, a **damaged** toy **cannot be restored** to its **initial condition**.
In simple words: Once a toy breaks, you cannot make it whole again. So, it is a change that cannot be undone.

Exam Tip: Changes that cannot be undone or brought back to their original state are called irreversible changes. Breaking an object is a common example.

Question 3. Some changes are given in the table below. Write in the blank space provided against each change whether it can be reversed or not?
Answer:

Exam Tip: Categorize changes as physical (often reversible) or chemical (often irreversible). Think about whether the substance's fundamental nature changes.

Question 4. Drawing changes the drawing sheet. Can you reverse this change?
Answer: **Creating a picture** **alters** the drawing sheet. If the **image** **is made** using a pencil, it can be **simply removed** with an eraser, and the sheet **regains** its **initial form**. In this **case**, it is **deemed** a **revertible alteration**. However, if the **picture is completed** with colors, the drawing sheet **cannot return** to its **initial state**. In this **case**, it is **regarded** as an **irrevertible alteration**.
In simple words: If you draw with a pencil, you can erase it and the paper is fine again, so that's reversible. But if you draw with colors, you can't erase them, and the paper is permanently changed, so that's irreversible.

Exam Tip: The reversibility of drawing depends on the medium used. Pencils allow for easy erasure, while inks or paints often cause permanent changes.

Question 5. Explain the difference between reversible and irreversible changes with examples.
Answer:

Exam Tip: Remember that physical changes usually involve a change in form but not composition, making them often reversible. Chemical changes form new substances and are typically irreversible.

Question 6. Plaster of Paris (POP) is applied as a coating on a cast over a broken bone. It hardens on drying, which prevents the broken bone from moving. Can this change in POP be reversed?
Answer: No, the **alteration** that **happened** in POP **cannot be undone**. Because: POP **chemically interacts** with water and **becomes** a **firm, new material**. Being a chemical **alteration**, it **is an unchangeable process**.
In simple words: No, the change in POP cannot be reversed. When POP mixes with water, it turns into a new, hard material, and you can't change it back.

Exam Tip: Hardening of POP is a chemical reaction. Generally, chemical changes are irreversible, as new substances with different properties are formed.

Question 7. A bag of cement was left open overnight and got wet due to rain. The next day, the sun came out. Can the change that occurred in the cement be reversed?
Answer: No, the **alteration** that **took place** in cement **cannot be undone**. Because: cement **chemically interacts** with water and **hardens**, becoming **rock-like**. Being a chemical **alteration**, it **is an unchangeable process**.
In simple words: No, the cement cannot be reversed once it gets wet and hardens. It mixes with water and turns into a solid, new substance, similar to a stone.

Exam Tip: Cement hardening is a chemical process that creates new compounds. This makes it an irreversible change, similar to the setting of POP.

Gseb Class 6 Science Changes Around Us Textbook Activities

Understanding Textbook Activities

Activity 1:

Demonstrating that inflating a balloon is a reversible change. Materials: Balloon.

Filling air in a balloon changes its size and shape.

Method:

• 1. Take a balloon.
• 2. Inflate it by blowing air into it with your mouth. Observe the change in the balloon's shape and size.
• 3. Now, release the air from it. Note what you observe.

Observation: The balloon regains its original state.

Conclusion: Inflating a balloon is a reversible change.

Activity 2:

Demonstrating that making an airplane by folding a piece of paper is a reversible change. Materials: Piece of paper.

Method:

• 1. Take a piece of paper.
• Toy airplane made by folding paper.
• 2. Make an airplane by folding it as shown in the figure.
• 3. Now, unfold the paper and straighten it.
• 4. You get the same paper as the original.

Observation: By folding the piece of paper correctly, an airplane is formed, and by straightening it, the paper is restored to its original form.

Conclusion: Making an airplane by folding a piece of paper is a reversible change.

Activity 3:

Demonstrating that rolling a roti from a ball of wheat flour dough is a reversible change. Materials: Wheat flour dough, rolling pin, rolling board.

Dough ball made from dough and rolled roti.

Method:

• 1. Make a small, round ball from the wheat flour dough.
• 2. Roll it out to make a roti.
• 3. Can the rolled roti be transformed back into a dough ball?

Observation: The rolled roti can be transformed back into a dough ball.

Conclusion: Rolling a roti from a ball of wheat flour dough is a reversible change.

Activity 4:

Demonstrating that the bursting of a balloon is an irreversible change. Materials: Balloon, sharp pencil, thread.

Method:

• 1. Take a balloon and inflate it to its full size.
• 2. Tie its opening with a thread.
• 3. Press the balloon with a sharp pencil. This will burst the balloon.
• 4. Do you get the original balloon back from the burst balloon?

Observation: The original balloon cannot be recovered from the burst balloon.

Conclusion: The bursting of a balloon is an irreversible change.

Activity 5:

Demonstrating that an airplane made by cutting a drawing of an airplane on paper is an irreversible change.

Materials: Paper, scissors.

Airplane cut from paper.

Method:

• 1. Take a piece of paper.
• 2. Draw an outline of an airplane on it.
• 3. Cut it along the outer line to obtain the shape of an airplane.
• 4. Do you get the original paper back from the cut airplane?

Observation: The original paper cannot be recovered from the cut airplane.

Conclusion: An airplane made by cutting paper is an irreversible change.

Activity 6:

Demonstrating that baking a rolled roti is an irreversible change. Materials: Rolled roti, griddle, gas stove.

Method:

• 1. Make a ball from dough and roll it into a roti with the help of a rolling pin and board.
• 2. Bake the rolled roti on a griddle. Do you get the rolled roti back from the baked roti?

Observation: The rolled roti cannot be recovered from the baked roti.

Conclusion: Baking a rolled roti is an irreversible change.

Activity 7:

Demonstrating that the burning of a candle is an irreversible change.

Materials: Candle, matchbox, ruler.

(a) Initially (b) After some time [Figure: Burning Candle]

Method:

• 1. Take a small candle and measure its length with a ruler.
• 2. Keep the candle upright and light it.
• 3. Let it burn for some time.
• 4. Now extinguish the candle. Measure its length again. Can the change in the candle's length be reversed?

Observation: As the candle burns, the wax is consumed, and thus the length of the candle decreases.

Conclusion: The burning of a candle is an irreversible change.