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What is a physical change?
What is a physical change?
A physical change alters the form or appearance of a substance but does not change its chemical composition.
Which of the following are examples of physical changes? (Select all that apply)
Which of the following are examples of physical changes? (Select all that apply)
Chemical changes can be easily reversed.
Chemical changes can be easily reversed.
False
What evidence may indicate a chemical change?
What evidence may indicate a chemical change?
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What defines a chemical property?
What defines a chemical property?
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What is density?
What is density?
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The formula for density is ____.
The formula for density is ____.
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Which of the following materials is considered an insulator?
Which of the following materials is considered an insulator?
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What is flammability?
What is flammability?
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What occurs during sedimentation?
What occurs during sedimentation?
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Study Notes
Physical Changes
- A physical change alters a substance's form or appearance without changing its chemical composition.
- Key characteristics include reversibility and no formation of new substances.
- Examples include:
- Melting: ice to water.
- Freezing: water to ice.
- Evaporation: water to steam.
- Condensation: steam to water.
- Sublimation: dry ice to carbon dioxide gas.
- Deposition: gas forming frost on a surface.
- Physical alterations such as cutting, bending, or crushing.
- Understanding physical changes is crucial for separating mixtures and studying matter.
Chemical Changes
- A chemical change results in the formation of new substances with different chemical compositions.
- Notable characteristics are irreversibility and the creation of new substances.
- Evidence of chemical change includes:
- Color change indicating a reaction.
- Gas production revealing a chemical process.
- Heat or light production signaling a reaction.
- Changes in smell or taste.
- Examples include:
- Burning wood in combustion.
- Rusting of iron when exposed to oxygen and water.
- Cooking, baking, and food digestion processes.
- Chemical changes are vital in natural processes and technological advancements.
Factors Affecting Chemical Change
- Temperature: Higher heat increases reaction rates.
- Concentration: Greater reactant concentration accelerates reactions.
- Catalysts: Substances that speed up reactions without being consumed.
- Surface area: Increased surface area enhances reaction rates.
Physical Properties
- Physical properties can be observed or measured without altering chemical composition.
- They include color, texture, odor, density, melting point, boiling point, magnetism, and conductivity.
Mass and Weight
- Mass is the quantity of matter in an object, measured in grams.
- Weight represents the force of gravity acting on an object, dependent on mass and gravitational field.
Volume
- Volume measures the space an object occupies, typically in milliliters or cubic centimeters.
Density
- Density is mass per unit of volume, indicating how closely packed matter is.
- Density formula: Density = Mass / Volume.
- Understanding density is key in predicting substance behavior (e.g., buoyancy).
Insulators and Conductors
- Insulators resist the flow of heat or electricity (e.g., wood, rubber).
- Conductors allow charge or heat flow easily (e.g., gold, copper, seawater).
Chemical Properties
- Chemical properties describe a substance's reactivity and involve changes in chemical composition.
- Observable only by altering the substance's makeup.
- Common examples include flammability, reactivity, acidity, and toxicity.
Flammability
- The ability of a substance to ignite (e.g., alcohol, methane).
Reactivity
- Describes how a substance interacts with others (e.g., oxidation with oxygen).
Acidity
- Reflects a substance's capacity to donate hydrogen ions (H+) (e.g., acid rain).
Toxicity
- The potential of a substance to harm organisms (e.g., mercury).
Sedimentation
- A process used to separate mixtures by allowing denser, insoluble particles to settle under gravity.
- Results in heavier particles settling at the bottom while lighter particles remain suspended.
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Description
This quiz explores the concept of physical changes, including definitions and key characteristics. Participants will learn about reversible changes and the various states of matter, with examples illustrating each concept. Test your understanding of how physical changes differ from chemical changes.
