Physical vs. Chemical change quick check
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To determine whether a change is a physical or chemical change, you can consider the following factors:
1. Nature of the change: Physical changes involve a change in appearance, form, or state of matter, but the substance itself remains the same chemically. Chemical changes, on the other hand, result in the formation of new substances with different properties.
2. Reversibility: Physical changes are usually reversible, meaning the original substance can be recovered without altering its chemical composition. Chemical changes, on the other hand, are often irreversible because new substances are formed.
3. Energy change: Physical changes generally do not involve any energy change, except for changes in state. Chemical changes, however, often require or release energy in the form of heat, light, or sound.
Here are some examples to help illustrate the differences:
Physical change:
- Melting an ice cube: The solid ice changes to liquid water, but no new substance is formed.
- Boiling water: The liquid water changes to water vapor (a gas), but the chemical composition of water remains the same.
Chemical change:
- Burning paper: The paper reacts with oxygen in the air and undergoes combustion, producing new substances like ash, smoke, and gases.
- Digesting food: The food you eat undergoes a series of chemical reactions in your body, breaking down into simpler compounds to release energy.
By analyzing these factors and considering the specific changes that occur, you can determine whether a given change is a physical or chemical change.
Physical change:
1. Definition: A physical change is a change in the physical properties of a substance, such as its shape, size, texture, or state of matter, without changing its chemical composition.
2. Examples: Melting ice, boiling water, cutting paper, crushing a can, dissolving sugar in water.
Chemical change:
1. Definition: A chemical change is a change in which one or more substances are converted into new substances with different chemical compositions and properties.
2. Examples: Burning wood, rusting of iron, baking a cake, digestion of food, photosynthesis.
Distinguishing factors between physical and chemical changes:
1. Reversibility: Physical changes are usually reversible, meaning the original substance can be recovered, while chemical changes are usually irreversible.
2. Changes in energy: Physical changes generally do not involve a significant change in energy, whereas chemical changes often involve the release or absorption of energy.
3. Formation of new substances: Physical changes do not result in the formation of new substances, whereas chemical changes involve the formation of new substances.
Remember that the distinction between physical and chemical changes is not always black and white, and some changes may exhibit characteristics of both.