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Questions and Answers
What is a common characteristic of the accidental discoveries of synthetics?
What is a common characteristic of the accidental discoveries of synthetics?
What is the main building block of a polymer?
What is the main building block of a polymer?
Which of the following is a natural material that contains polymers?
Which of the following is a natural material that contains polymers?
What is a common property of polymers?
What is a common property of polymers?
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What is an advantage of synthetic fibers?
What is an advantage of synthetic fibers?
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What is the definition of a physical change?
What is the definition of a physical change?
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What is a type of synthetic food?
What is a type of synthetic food?
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What is a reactant?
What is a reactant?
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What is characteristic of an endothermic reaction?
What is characteristic of an endothermic reaction?
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What is an example of an endothermic reaction?
What is an example of an endothermic reaction?
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What is a factor that affects the rate of a reaction?
What is a factor that affects the rate of a reaction?
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What is an example of a chemical change?
What is an example of a chemical change?
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What is a characteristic of a synthetic material?
What is a characteristic of a synthetic material?
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What is an example of an exothermic reaction?
What is an example of an exothermic reaction?
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What is a characteristic of a natural resource?
What is a characteristic of a natural resource?
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What is the effect of increasing the surface area on the rate of a reaction?
What is the effect of increasing the surface area on the rate of a reaction?
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Study Notes
Physical and Chemical Changes
- Physical change: alters the form or appearance of a substance without changing it into a different substance
- Examples: cutting, crushing, melting, freezing, boiling
Chemical Changes
- Chemical change: produces one or more new substances
- Examples: burning, rusting, cooking, digestion, decomposition
Reactants and Products
- Reactants: substances that undergo chemical changes
- Products: substances formed as a result of a chemical reaction
Exothermic and Endothermic Reactions
- Exothermic reaction: energy released as products form is greater than energy required to break bonds of reactants
- Feels warm
- Examples: campfire, nuclear fission
- Endothermic reaction: more energy required to break bonds of reactants than is released by formation of products
- Feels cold
- Examples: melting ice, photosynthesis
Indicators of Chemical Reaction
- Changes that indicate a chemical reaction took place:
- Color change
- Odor change
- Gas production
- Formation of a precipitate
Factors Affecting Rate of Reaction
- Five factors that affect the rate of a reaction:
- Temperature: increasing temperature increases rate of reaction
- Surface area: increasing surface area increases rate of reaction
- Catalysts: substances that speed up a chemical reaction
- Inhibitors: substances that slow down reactions
Synthetic Materials and Natural Resources
- Synthetic material: chemicals and resources made by humans
- Examples: nylon, spandex, rayon
- Natural resource: anything naturally occurring in the environment that humans use
- Examples: pure elements, simple molecules, complex molecules
Pure Substances
- Characteristics of pure substances:
- Same type of atom
- Same molecules
- Same ionically bonded elements
- Examples: pure elements, simple molecules, complex molecules
Accidental Discoveries of Synthetics
- Three accidental discoveries of synthetics:
- Superglue: cyanoacrylate that stuck to everything
- Non-stick coating: white flakes in a container instead of gas
- Artificial sweetener: forgetting to wash hands before eating
Polymers
- Polymer: long chains of molecules made up of repeating units called monomers
- Natural occurrence of polymers:
- Wool
- Silk
- Rubber
- Cellulose
- Properties of polymers:
- Strength
- Flexibility
- Elasticity
Synthetic Fibers
- Four types of synthetic fibers:
- Acrylic
- Nylon
- Polyester
- Spandex
- Four advantages of synthetic fibers:
- Less expensive
- Last longer
- Dry more quickly
- Clean easily
- Strong and flexible
- Three drawbacks of synthetic fibers:
- Burn more easily
- Pollutants
- Can cause allergies
- Four ways in which synthetic fibers are used:
- Clothes
- Buildings
- Materials for goods
- Plastics
Synthetic Foods
- Three types of synthetic foods:
- Flavorings
- Colorings
- Preservatives
- Four advantages of synthetic foods:
- Cheaper
- Foods last longer
- Safer to consume
- Obtain in a large scale
- One drawback of synthetic foods:
- Health risks
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Description
Practice questions on physical and chemical changes, reactants, and products for 8th grade chemistry exam.
