Write a paragraph explaining your understanding of physical and chemical changes. Provide a specific example of each and explain the evidence that supports your analysis that a physical or chemical change has occurred.
Physical changes refer to alterations in the physical states or properties of matter, such as shape, size, or phase, without changing its chemical composition. They are usually reversible. An example of a physical change is melting ice. When ice is heated, it changes from a solid state to a liquid state, but its chemical composition remains the same. The evidence that supports this analysis is that if the liquid water is cooled, it will solidify back into ice. On the other hand, chemical changes involve the rearrangement of atoms to form new substances with different chemical properties or compositions. These changes are usually irreversible. A common example of a chemical change is burning paper. When paper is burned, it undergoes a chemical reaction called combustion, leading to the formation of new compounds (ash, smoke, and gases). The evidence supporting this analysis is that once paper has burned, it cannot be converted back into its original form by simply cooling or reversing the process.
Physical changes involve a transformation of matter that does not affect its chemical composition. These changes only alter the physical properties of a substance, such as its shape, size, state of matter, or texture. An example of a physical change is when ice melts to become liquid water. The evidence supporting this analysis is that despite the change in state, the water molecules still consist of the same combination of hydrogen and oxygen atoms. On the other hand, chemical changes involve the formation of new substances with different chemical compositions. This change occurs at the molecular level, resulting in a transformation that is not easily reversible. For instance, when wood is burned, it undergoes a chemical change as it reacts with oxygen in the air to produce heat, light, and new compounds like carbon dioxide and ash. The evidence for this change lies in the fact that the properties of the original wood, such as its shape and texture, no longer exist, and new substances with different physical properties are formed.
