How are chemical changes different from physical changes?(1 point)
Responses
They form new substances.
They form new substances.
They involve heat.
They involve heat.
They are reversible.
They are reversible.
They include shifts in the phase of matter.
They include shifts in the phase of matter.
Chemical changes are different from physical changes in several ways:
1. They form new substances: Unlike physical changes, chemical changes result in the formation of new substances with different properties. Bonds between atoms or molecules are broken and new ones are formed, leading to a chemical reaction.
2. They involve heat: Chemical changes often involve the absorption or release of heat energy. This is because breaking and forming bonds requires energy. Physical changes, on the other hand, may involve temperature changes without the formation of new substances.
3. They are reversible or irreversible: Physical changes are typically reversible, meaning the original substance can be restored without altering its chemical composition. In contrast, chemical changes are often irreversible, as the formation of new substances cannot easily be reversed.
4. They include shifts in the phase of matter: Physical changes involve changes in the state or phase of matter, such as converting a solid to a liquid or a gas. Chemical changes may also involve changes in state, but this is not a defining characteristic. The formation of new substances and the alteration of chemical composition are the primary distinctions of chemical changes.
The correct answer is: They form new substances.
Chemical changes are different from physical changes because they involve the formation of new substances. In a chemical change, the atoms or molecules of the substances rearrange themselves to form different compounds, resulting in the formation of new substances with different properties than the original substances. For example, when iron rusts, it undergoes a chemical change and forms a new substance, iron oxide.
Physical changes, on the other hand, do not involve the formation of new substances. Instead, they only affect the physical properties of a substance, such as its shape, size, or state of matter. Physical changes can be reversible, meaning the substance can return to its original state, while chemical changes are often irreversible.
The other responses, involving heat and shifts in the phase of matter, are not defining characteristics that differentiate chemical changes from physical changes. Heat can be involved in both types of changes, and shifts in the phase of matter, such as melting or boiling, are examples of physical changes rather than chemical changes.