Final answer:
Melting of ice and dissolving sugar in water are classified as physical changes because no new substances are formed. Burning of wood and rusting of iron are classified as chemical changes as they result in the formation of new substances.
Step-by-step explanation:
Classifying Physical and Chemical Changes
To classify each given change as physical or chemical, we consider the characteristics of each type of change:
- Physical changes do not alter the chemical composition of a substance and are usually reversible; examples include phase changes and dissolving.
- Chemical changes involve a substance reacting to form a new substance, accompanied by changes in energy and often not easily reversed; examples include burning, rusting, and decomposing.
Now, let's classify each of the provided changes:
- Melting of ice - Physical change: Ice is simply changing from solid to liquid form; no new substance is formed.
- Burning of wood - Chemical change: Wood reacts with oxygen to form ash, carbon dioxide, and water vapor; new substances are formed and energy is released.
- Dissolving sugar in water - Physical change: Sugar molecules are dispersed within the water, but no new substance is created and this process is often reversible.
- Rusting of iron - Chemical change: Iron reacts with oxygen in the presence of water to form iron oxide (rust), a new substance.