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Questions and Answers
What is a Physical Change?
What is a Physical Change?
Substance undergoes changes in physical characteristics like size, shape and color. Molecules don't change. No new substance formed. Physical changes are mostly reversible.
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)
- Water freezing (correct)
- Iron rusting
- Fuel burning
- Wax melting (correct)
What is a Chemical Change?
What is a Chemical Change?
Two substances react chemically, forming a new substance with different chemical properties. Chemical changes are mostly irreversible.
Which of the following are examples of Chemical Changes? (Select all that apply)
Which of the following are examples of Chemical Changes? (Select all that apply)
What is a Chemical Reaction?
What is a Chemical Reaction?
What are Reactants?
What are Reactants?
What are Products?
What are Products?
The scientific significance of studying chemical reactions is to create new and useful substances such as ___, plastics, and medicines.
The scientific significance of studying chemical reactions is to create new and useful substances such as ___, plastics, and medicines.
What is Rusting of Iron?
What is Rusting of Iron?
How can rusting be prevented?
How can rusting be prevented?
What is Galvanization?
What is Galvanization?
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Study Notes
Physical Change
- Involves alterations in size, shape, and color without changing molecular structure.
- No new substance is formed; changes are mostly reversible.
Examples of Physical Changes
- Water freezing, wax melting, tearing paper, boiling water, breaking a tumbler.
Chemical Change
- Occurs when substances react chemically to form a new substance with different properties.
- These changes are generally irreversible.
Examples of Chemical Changes
- Fuel burning, cooking food, iron rusting, reaction of iron and sulfur to form iron sulfide upon heating.
Chemical Reaction
- Defined as the process where substances undergo transformation to create new substances.
Reactants
- The initial substances that participate in a chemical reaction.
Products
- The new substances that result from a chemical reaction.
Scientific Significance of Chemical Reactions
- Essential for understanding substance properties and creating new materials.
- Enabled innovations in ceramics, plastics, and medicines due to extensive research in chemical changes.
Rusting of Iron
- Rust is a reddish-brown substance formed when iron is exposed to moisture and air over time.
- The process involves iron reacting with water and oxygen to produce iron oxide.
- Rusting is particularly problematic for ships due to constant water exposure, leading to significant monetary loss.
Prevention of Rusting
- Rusting can be prevented by applying a layer of paint, oil, or grease; however, if these protective layers crack, rust formation occurs.
Galvanization
- A highly effective method of rust prevention by depositing a protective layer of zinc or chromium.
- Commonly applied to water pipes to enhance durability.
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