Exploring Physical Changes

• Physical and chemical changes are explored.

Physical Change

• A physical change does not create a new substance.
• The material remains the same, but with a different appearance.
• Ice melting into water is a physical change.
• The substance remains water (H₂O), but changes from solid to liquid.
• The melting point is the temperature at which a solid turns to liquid.
• Evaporation is when a liquid turns into a gas.
• Evaporation occurs when molecules gain enough energy to break free from a liquid's surface and become a gas.
• Condensation is the process when a liquid forms from gas or vapor.
• Water vapor condenses when moist air is cooled below its dew point.
• Dew point is the temperature at which moist air becomes saturated and forms dew.
• Solidification, or freezing, is when a liquid turns into a solid.
• Solidification happens when the temperature decreases to its freezing point.
• During solidification, molecules lose energy and arrange into a more structured, solid form.
• Sublimation is a change of state from solid to gas without passing the liquid state.
• Sublimation occurs when the molecules of a solid gain enough energy to overcome their fixed positions and enter the gaseous state.

Chemical Change

• A chemical change transforms substances into new and different ones.
• Unlike physical changes, chemical changes form new materials with different properties.
• Chemical reactions are processes where chemicals interact to form new chemicals with different compositions.
• New substances are formed as a characteristic of chemical change.
• Gas, heat, light, or solids (precipitate) can be produced.
• Chemical changes are usually irreversible, and lead to large energy changes.

Evidences of Chemical Reaction

• Combustion is the process of burning wood or fossil fuels.
• Rusting is iron reacting with oxygen to form rust.
• Cooking/baking transforms raw ingredients into cooked food.
• Digestion breaks down food in the stomach to provide energy.
• Neutralization is when acid reacts with a base to form salt and water.
• Changes in Intrinsic Property occur during chemical changes.
• Production of light.
• Evolution of gas occurs due to a chemical change.
• Temperature Change can provide evidence of chemical reaction.
• Formation of Precipitate.