Grade 2 science worksheet on reversible and irreversible changes, asking students to identify whether each illustrated change can be undone.

Problem Explanation:

The task is to determine whether each of the given changes is reversible or irreversible. A reversible change is one that can be undone, while an irreversible change cannot be changed back to its original state.

Steps to Solve:

1. Understand the Definitions:
- Reversible Change: Can be undone or reversed.
- Irreversible Change: Cannot be undone or reversed.

2. Analyze Each Scenario:
Let's evaluate each scenario based on whether the change can be reversed:

#### 1. Cooking an egg
- When an egg is cooked, the proteins in the egg white and yolk denature (change their structure permanently). This process cannot be reversed; you cannot "uncook" an egg.
- Answer: Irreversible (I)

#### 2. Mixing cement
- Cement mixing involves combining dry cement with water, which triggers a chemical reaction that hardens the mixture into concrete. Once this reaction occurs, it cannot be reversed.
- Answer: Irreversible (I)

#### 3. Ice melting into water
- Melting ice is a physical change where solid ice turns into liquid water due to an increase in temperature. This process is reversible because the water can be frozen back into ice by lowering the temperature.
- Answer: Reversible (R)

#### 4. Burning wood
- Burning wood is a chemical reaction where wood combines with oxygen to produce carbon dioxide, water vapor, and ash. This process is irreversible because the original wood cannot be recovered from the ashes and gases produced.
- Answer: Irreversible (I)

#### 5. A puppy growing into a dog
- Growth is a biological process that involves cells dividing and maturing. This process is irreversible because a dog cannot revert back to being a puppy.
- Answer: Irreversible (I)

#### 6. Freezing juice into a popsicle
- Freezing juice into a popsicle is a physical change where the liquid juice becomes a solid. This process is reversible because the popsicle can be melted back into juice by increasing the temperature.
- Answer: Reversible (R)

#### 7. Blowing up a balloon
- Blowing up a balloon involves stretching the rubber material to contain air. This is a physical change that can be reversed by releasing the air, allowing the balloon to return to its original shape.
- Answer: Reversible (R)

#### 8. Fireworks exploding
- Fireworks exploding is a chemical reaction involving the combustion of chemicals to produce light, sound, and smoke. This process is irreversible because the chemicals are consumed and transformed into different substances.
- Answer: Irreversible (I)

Final Answers:

- Cooking an egg: I
- Mixing cement: I
- Ice melting into water: R
- Burning wood: I
- A puppy growing into a dog: I
- Freezing juice into a popsicle: R
- Blowing up a balloon: R
- Fireworks exploding: I

Boxed Answer:

\[
\boxed{
\begin{array}{cccc}
\text{Cooking an egg} & \text{Mixing cement} & \text{Ice melting into water} & \text{Burning wood} \\
\text{I} & \text{I} & \text{R} & \text{I} \\
\text{A puppy growing into a dog} & \text{Freezing juice into a popsicle} & \text{Blowing up a balloon} & \text{Fireworks exploding} \\
\text{I} & \text{R} & \text{R} & \text{I} \\
\end{array}
}
\]