Question 26
Are the following examples of chemical or physical changes?
Column A.
1. A sliver spoon tarnishing
2. Blowing a dandelion
3. Building a sand castle
4. Toasting bread
Column B.
A. Chemical change
B. Physical change
Column A:
1. Chemical change
2. Physical change
3. Physical change
4. Chemical change
Column B:
1. A. Chemical change
2. B. Physical change
3. B. Physical change
4. A. Chemical change
Column A:
1. A silver spoon tarnishing - A chemical change
2. Blowing a dandelion - A physical change
3. Building a sand castle - A physical change
4. Toasting bread - A chemical change
Column B:
A. Chemical change
B. Physical change
To determine whether the examples given are chemical or physical changes, we need to understand the difference between the two.
A physical change is a change in a substance that does not involve a change in its chemical composition. The substance remains the same, but its physical properties may be altered. Examples of physical changes include changes in size, shape, state of matter, or phase transitions (melting, freezing, boiling, etc.).
On the other hand, a chemical change, also known as a chemical reaction, involves a change in the chemical composition of a substance. New substances are formed with different chemical properties. Some common signs of a chemical change include a change in color, formation of gas or bubbles, release or absorption of heat, formation of a precipitate, or emission of light.
Let's examine each example:
Column A:
1. A silver spoon tarnishing - This is a chemical change. Over time, silver reacts with sulfur and oxygen in the air to form silver sulfide, which appears as a dark tarnish on the spoon's surface.
2. Blowing a dandelion - This is a physical change. Blowing a dandelion simply disperses the seeds, altering their location. The composition and chemical properties of the seeds remain the same.
3. Building a sand castle - This is a physical change. Building a sand castle involves arranging and shaping grains of sand, but the chemical composition of the sand itself remains unaffected.
4. Toasting bread - This is a chemical change. When bread is toasted, a chemical reaction called the Maillard reaction occurs. The heat causes sugars and proteins in the bread to undergo a series of complex reactions, resulting in the browning and flavor changes we associate with toasted bread.
Based on this analysis, the answers would be as follows:
Column A:
1. Chemical change (A)
2. Physical change (B)
3. Physical change (B)
4. Chemical change (A)