a) What physical change in the wood has taken place during the preparation of the
campfire?
Answers
Recall that physical properties are displayed in the look or feel of a substance. The composition of the substance is not changed. Examples of physical properties could include color, mass, volume, density, texture, state or phase, melting point, boiling point, hardness, conductivity, and viscosity. When wood is cut into firewood, this is a physical change. The composition of the wood stays the same. In a physical change, the substance usually can be changed back into its original form.
What about chemical properties? These properties can be observed only when the substance changes into one or more different substances through chemical reactions or transformations. This is the process of chemical change. Examples of chemical properties are flammability (a material's ability to burn in the presence of oxygen) and reactivity (how easily a material combines chemically with other materials). Imagine that you’re watching a log burning in a fireplace. One of the chemical properties of carbon-based wood is that it has the ability to burn. Wood changes chemically to carbon dioxide when it burns and leaves a residue of ashes. These ashes cannot be changed back to wood. When air and water act on an object made of iron, a new substance, rust, is formed. Rust is a different substance than iron. Chemical changes result in new substances.