Lesson 1.05 Flashcards
(26 cards)
What is a physical change?
A physical change is a change in a substance from one form to another without changing its composition.
What is a chemical change?
On the other hand, when chemical changes occur, new substances are produced that usually have different properties than the original substances.
List examples of physical changes
Whether the balloon is inflated or deflated, it is still a balloon. Ripping a sheet of paper, breaking a window, or taking a piece of clay and transforming it into a new shape are other examples of physical changes.
Compare what happens to molecules in physical vs. chemical changes.
Physical Change: The molecules stay the same but the shape and phase changes.
Chemical Change: The actual make up and structure of the molecules change forming new substances.
What are some signs scientists look for to indicate that a chemical change may have occurred?
- production of flames
- color change
- bubbling or fizzing
- temperature change
- smoke
- production of light
- formation of a substance in a different state (for example, a solid from the mixing of two liquids)
Why is it important to do further investigations to determine if a chemical change really occurred?
Sometimes this chemical change is easy to see and identify, while other times an investigation is required to identify if a new substance has formed. Recognizing when a chemical reaction has occurred allows you to identify chemical changes.
Describe how molecular motion and distance between molecules change as ice is heated to become a liquid and then a gas.
Instead, the motion of water molecules increases due to the transfer of heat to kinetic energy within the molecules. As the molecules move faster, they collide more, and the space between the molecules increases.
Evaporation
the phase transition of a substance from a liquid to a gas, which takes place at the surface of the liquid
Condensation
the phase transition of a substance from a gas to a liquid
Melting
Going from a solid to a liquid. Heat is absorbed.
Freezing
going from a liquid to a solid. Heat is released.
Sublimation
Going directly from a solid to a gas. For example, dry ice.
Deposition
Going directly from a gas to a solid.
Identify each of the following as a physical or chemical change.
Continued >
Burning a match
Chemical Change
Freezing ice
Physical Change
Breaking glass
Physical Change
Dissolving sugar in water
Physical Change
Boiling water
Physical Change
Rusting iron
Chemical Change
Baking a cake
Chemical Change
Reacting vinegar with baking soda
Chemical Change
When the chemicals iron sulfide (FeS) and hydrochloric acid (HCl) are combined, bubbles appear from the mixture.
Continued >
Does the appearance of bubbles indicate a physical or chemical change?
That a chemical change is occurring.
