Physical Changes in Science Flashcards

Physical Changes

• A physical change involves a change in one or more physical properties without forming a new substance; the identity of matter remains the same.
• Cutting a pizza in half or melting an ice cube are examples of physical changes.
• When an ice cube melts, it transitions from solid to liquid, but remains water—a change of state, illustrating a physical change.
• A piece of paper cut in half remains paper; only its size has changed.

Conservation of Mass

• In a lab involving mass conservation, the total mass remains unchanged before and after a rearrangement of materials, indicating no mass is gained or lost.
• Conservation of mass applies to both physical and chemical changes, ensuring mass is consistent throughout the process.

Chemical Properties and Changes

• A chemical property describes characteristics that can be observed only during a change to a different substance, such as the ability to rust or burn.
• A chemical change results in the formation of new substances with different physical and chemical properties; examples include a nail rusting or a reaction between baking soda and vinegar.

Signs of Chemical Changes

• Key indicators of a chemical change include:
  • Formation of a precipitate
  • Color or odor change
  • Temperature change
  • Production of bubbles
  • Energy change

Comparing Physical and Chemical Changes

• Both types of changes involve alterations in matter, but physical changes do not create new substances, while chemical changes do.
• Physical changes are reversible (e.g., freezing and melting), whereas chemical changes often produce irreversible transformations.

Heat and Chemical Reactions

• Removing heat from a system generally slows down chemical reactions, as evidenced by food preservation techniques like refrigeration or freezing.

Reactivity

• Reactivity refers to a substance's ability to undergo a chemical change, crucial for understanding how different materials interact during chemical processes.