4.4 Physical and Chemical Changes

• What is the key difference between physical and chemical changes?

  Chemical composition change
• What happens to the chemical composition of a substance during a chemical change?

  It changes
• Chemical changes are irreversible
• Chemical changes involve the rearrangement of atoms and breaking of bonds.


  True
• Chemical changes involve a change in the chemical composition
• Chemical changes involve significant energy
• What is an indicator of a physical change?

  Change in state
• What happens to the chemical composition of a substance during a physical change?

  It remains unchanged
• Match the type of change with its properties:

  Physical change ↔️ No change in composition

  Chemical change ↔️ Irreversible
• Burning wood is an example of a chemical change.


  True
• Physical changes alter the chemical identity of a substance.

  False
• Order the indicators of chemical changes from most common to least common.

  1️⃣ Color Change

  2️⃣ Gas Evolution

  3️⃣ Precipitate Formation

  4️⃣ Temperature Change

  5️⃣ Odor Change
• Chemical changes involve the breaking and forming of bonds
• Chemical changes are typically irreversible
• What is the defining characteristic of chemical changes?

  Change in chemical composition
• Chemical changes are typically irreversible.


  True
• Chemical changes involve significant energy changes
• What is the role of chemical reactions in chemical changes?

  Rearrange atoms and bonds
• Physical changes are reversible, while chemical changes are irreversible
• Gas evolution during a chemical reaction produces visible bubbles
• A temperature change during a chemical reaction indicates that energy is being absorbed or released
• What does an odor change indicate in a chemical reaction?

  New substances formed
• When salt dissolves in water, it remains sodium chloride
• Match the chemical change with its description:

  Burning wood ↔️ Produces ash, smoke, and gases

  Rusting of iron ↔️ Forms iron oxide

  Photosynthesis ↔️ Converts carbon dioxide and water into glucose and oxygen
• Plants use sunlight to convert carbon dioxide and water into glucose and oxygen
• Cutting vegetables is an example of a physical change in everyday life.

  True
• A change in color is always an indicator of a chemical change.

  False
• Match the property with the correct type of change:

  Reversibility ↔️ Physical changes

  Irreversibility ↔️ Chemical changes
• Physical changes are reversible
• What is the key feature of chemical changes regarding composition?

  Formation of new substances
• Steps of a chemical change in photosynthesis

  1️⃣ Carbon dioxide and water react

  2️⃣ Atoms are rearranged

  3️⃣ Bonds are broken and formed

  4️⃣ New substances are formed
• What happens to atoms and bonds in a chemical reaction during a chemical change?

  Atoms are rearranged
• Which property distinguishes chemical changes from physical changes in terms of reversibility?

  Irreversible
• Match the property with the type of change:

  Significant energy changes ↔️ Chemical change

  Reversible ↔️ Physical change
• Gas evolution is an indicator of a chemical change.

  True
• Order the steps involved in distinguishing physical and chemical changes:

  1️⃣ Observe the process

  2️⃣ Identify any changes in composition

  3️⃣ Determine reversibility

  4️⃣ Analyze energy changes
• What happens to the appearance of a substance during a physical change?

  It may change
• What are physical changes characterized by?

  No change in composition
• What are chemical changes defined by?

  Formation of new substances
• Physical changes affect only physical properties like state and shape.

  True