What has a physical and chemical change at the same time, apart from a candle
burning wood.
To identify a substance or process that involves both a physical and chemical change simultaneously, we need to understand the differences between the two types of changes.
A physical change relates to a modification in the physical properties of a substance, such as its shape, size, or state of matter, without altering its chemical composition. Examples can include changes in temperature, pressure, or physical state (such as melting, freezing, or evaporating).
On the other hand, a chemical change occurs when the identity and composition of a substance are altered as a result of a chemical reaction. Chemical changes involve the breaking and forming of chemical bonds, resulting in the creation of new substances with different properties than the starting materials.
In the case of burning wood, the transformation involves both physical and chemical changes simultaneously. Here's an explanation of the changes that occur during this process:
1. Physical change: Initially, when wood is exposed to heat, it undergoes a physical change known as pyrolysis. This process involves the decomposition of wood due to the application of heat, resulting in the release of gases, such as water vapor, carbon dioxide, and volatile organic compounds. The physical state of the wood changes from solid to gas without any alteration in its chemical composition.
2. Chemical change: Once the wood has undergone pyrolysis, the remaining solid residue, called charcoal, undergoes a chemical change when exposed to sufficient oxygen. This process is called combustion. The carbon in the charcoal reacts with oxygen to form carbon dioxide gas. The chemical bonds within the wood and charcoal break and reform during this reaction, resulting in the release of energy in the form of heat and light.
By examining these processes, we can see that burning wood involves both a physical change (pyrolysis) and a chemical change (combustion) occurring simultaneously.