Questions and Answers
Describe the process of a physical change.
Physical change occurs when objects or substances undergo a change that does not change their chemical composition.
What is the difference between a physical change and a chemical change? Give an example of each.
A physical change does not change composition while a chemical change results in a new substance. Chemical examples: burning and cooking; Physical examples: boiling and melting.
When a substance undergoes a chemical change, can it be reversed? Why?
Rarely, as most are permanent due to the rearrangement of atoms and molecules.
What are five common phase changes of matter?
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How do you recognize substances that have gone through physical or chemical changes?
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Describe some common chemical properties of matter.
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How is understanding reactivity helpful for making jewelry?
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What is flammability? Why do builders avoid using flammable materials in homes?
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What is toxicity? Give an example of something from your home.
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What is the difference between flammability and heat of combustion?
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What are some natural processes that represent physical and chemical changes?
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What are the differences between a physical change and a chemical change?
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List examples of physical changes.
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Study Notes
Physical Changes
- A physical change involves alterations that do not result in a change of chemical composition. Examples include changes in density, shape, size, solubility, malleability,compressibility, and phase changes.
- Examples of physical changes include boiling, melting, freezing, and shredding.
Chemical Changes
- A chemical change results in the formation of new substances through alterations in molecular composition. Examples include burning, cooking, rusting, and rotting.
- Chemical changes are rarely reversible because they often involve rearrangement of atomic structure.
Phase Changes
- Evaporation: Transition from liquid to gas, occurring on the surface with increased speed when heated.
- Melting: Process where solid turns into liquid at its melting point, as seen when ice melts.
- Condensation: Gas to liquid conversion, occurs when gas molecules attach to surfaces, like moisture on plants in cooler temperatures.
- Freezing: Change from liquid to solid at the freezing point; examples include snow and ice formation.
- Sublimation: Solid to gas transition without passing through the liquid phase, common with substances like dry ice.
Recognition of Changes
- Physical changes are generally reversible (e.g., melting ice), while chemical changes produce new substances that cannot revert to their original form.
Chemical Properties of Matter
- Key chemical properties include reactivity, flammability, toxicity, and heat of combustion.
- Extensive properties (vary with quantity): include mass, weight, and volume.
- Intensive properties (independent of quantity): include color, melting point, boiling point, and electrical conductivity.
Importance of Reactivity in Jewelry
- Low reactivity materials, such as gold and platinum, are preferred in jewelry due to their resistance to rust and tarnishing.
- High reactivity materials may pose risks, such as spontaneous combustion or toxicity.
Flammability
- Refers to how easily a substance ignites. Builders avoid flammable materials to prevent fire hazards in homes.
Toxicity
- Describes a substance's potential to cause harm to organisms. An example includes mercury.
Flammability vs. Heat of Combustion
- Flammability indicates how easily a substance can catch fire, while heat of combustion measures the amount of heat released during combustion.
Natural Processes
- Physical changes: Mixing salt or sand with water, melting, boiling, cutting, and shredding are typically reversible, meaning substances retain their original composition.
- Chemical changes: Include processes like burning wood, cooking eggs, baking, or souring milk, which result in new substances.
Summary of Changes
- Physical changes alter forms or shapes without creating new compounds, whereas chemical changes result in the production of new substances.
Examples of Physical Changes
- Dissolving honey in a drink illustrates a physical change because the honey remains chemically the same. Other examples include cutting wood, bending metal, and the transformation of a caterpillar into a butterfly.
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Description
Explore the differences between physical and chemical changes through engaging flashcards. This quiz will help you understand key concepts such as definitions, examples, and types of changes in matter. Perfect for students looking to reinforce their knowledge in science.
