How are chemical changes different from physical changes?(1 point)
Responses
They form new substances.
They form new substances.
They are reversible.
They are reversible.
They include shifts in the phase of matter.
They include shifts in the phase of matter.
They involve heat.
They involve heat.
Chemical changes are different from physical changes in several ways:
1. They form new substances: Chemical changes involve the formation of new substances with different chemical properties. This means that the chemical composition of the matter changes.
2. They are irreversible: Unlike physical changes which can often be reversed, chemical changes are usually not easily reversible. Once a chemical change occurs, it is difficult or impossible to revert the substances back to their original form.
3. They include shifts in the phase of matter: While physical changes can involve changes in the state or phase of matter (e.g., melting, boiling), chemical changes can also result in changes in the phase of matter, such as the formation of solids, liquids, or gases.
4. They involve heat: Chemical changes often require the addition or release of heat energy. This is because chemical reactions involve the breaking and forming of chemical bonds, which require energy to be either absorbed or released.
To understand the difference between chemical changes and physical changes, we need to look at their characteristics.
Chemical changes:
1. Form new substances: One of the key differences between chemical changes and physical changes is that chemical changes result in the formation of new substances with different chemical properties. This means that the atoms or molecules rearrange themselves, forming new bonds and creating entirely new chemical compounds.
Physical changes:
1. Reversibility: Physical changes, unlike chemical changes, are generally reversible. This means that the original substance can be obtained again by reversing the physical change that occurred. For example, melting an ice cube to obtain liquid water is a physical change, and the water can be frozen back into ice.
2. Shifting of phase: Physical changes often involve shifts in the phase of matter, such as melting, freezing, boiling, or condensation. In these changes, the substance retains its chemical identity, but its physical state or arrangement may change.
3. Involvement of heat: Physical changes can be accompanied by the absorption or release of heat, but heat is not a defining characteristic of physical changes. Examples of physical changes involving heat include heating or cooling a substance to change its temperature or phase.
In summary, chemical changes involve the formation of new substances, are not easily reversible, and are not solely dependent on heat. On the other hand, physical changes are generally reversible, can involve shifts in the phase of matter, and may involve heat, but heat is not essential for identifying a physical change.
How does a balanced chemical equation demonstrate the Law of Conservation of Mass?(1 point)
Responses
it shows that no atoms have been gained or lost during the reaction
it shows that no atoms have been gained or lost during the reaction
it shows that the properties of the elements stay the same after the reaction
it shows that the properties of the elements stay the same after the reaction
it shows that only physical changes follow the Law of Conservation of Mass
it shows that only physical changes follow the Law of Conservation of Mass
it shows that all compounds remain bonded after the reaction