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All questions of Nature of Matter: Elements, Compounds, and Mixtures for Class 8 Exam
Which of the following statements about elements is true?- a)They consist of only one type of atom.
- b)They are always found in compounds.
- c)They have variable compositions.
- d)They can be broken down into simpler substances.
Correct answer is option 'A'. Can you explain this answer?
Which of the following statements about elements is true?
a)
They consist of only one type of atom.
b)
They are always found in compounds.
c)
They have variable compositions.
d)
They can be broken down into simpler substances.
 | C K Academy answered |
Elements consist of only one type of atom and cannot be broken down into simpler substances by chemical means. Each element has unique properties and is represented on the periodic table.
Which of the following is a native mineral?- a)Calcite
- b)Gold
- c)Quartz
- d)Talc
Correct answer is option 'B'. Can you explain this answer?
Which of the following is a native mineral?
a)
Calcite
b)
Gold
c)
Quartz
d)
Talc
 | EduRev Class 8 answered |
Gold is an example of a native mineral because it occurs naturally in its elemental form. Other examples include silver and copper. In contrast, quartz and calcite are compound minerals made of two or more elements.
What is the primary component of air?- a)Argon
- b)Oxygen
- c)Nitrogen
- d)Carbon dioxide
Correct answer is option 'C'. Can you explain this answer?
What is the primary component of air?
a)
Argon
b)
Oxygen
c)
Nitrogen
d)
Carbon dioxide
 | Nidhi Bhatt answered |
Nitrogen is the primary component of air, making up about 78% of the atmosphere. While oxygen and carbon dioxide are also present, nitrogen is the most abundant gas in air.
Which of the following is NOT a type of pure substance?- a)Compound
- b)All of the above are pure substances
- c)Element
- d)Mixture
Correct answer is option 'D'. Can you explain this answer?
Which of the following is NOT a type of pure substance?
a)
Compound
b)
All of the above are pure substances
c)
Element
d)
Mixture
| | EduRev Class 8 answered |
A mixture is not a pure substance; it consists of two or more different substances combined together. In contrast, elements and compounds are classified as pure substances because they contain only one type of particle.
What is the difference between homogeneous and heterogeneous mixtures?- a)Homogeneous mixtures are visible; heterogeneous are not.
- b)Heterogeneous mixtures are chemically bonded; homogeneous are not.
- c)Homogeneous mixtures have uniform composition; heterogeneous do not.
- d)There is no difference; they are the same.
Correct answer is option 'C'. Can you explain this answer?
What is the difference between homogeneous and heterogeneous mixtures?
a)
Homogeneous mixtures are visible; heterogeneous are not.
b)
Heterogeneous mixtures are chemically bonded; homogeneous are not.
c)
Homogeneous mixtures have uniform composition; heterogeneous do not.
d)
There is no difference; they are the same.
| | C K Academy answered |
The key difference is that homogeneous mixtures have a uniform composition throughout, meaning the components are indistinguishable, while heterogeneous mixtures consist of visibly different substances that can be easily separated.
Which of the following is a characteristic of a compound?- a)It can be separated by physical means.
- b)It retains the properties of its constituent elements.
- c)It consists of mixtures of elements.
- d)It has a fixed composition and unique properties.
Correct answer is option 'D'. Can you explain this answer?
Which of the following is a characteristic of a compound?
a)
It can be separated by physical means.
b)
It retains the properties of its constituent elements.
c)
It consists of mixtures of elements.
d)
It has a fixed composition and unique properties.
 | Ruchi Desai answered |
Understanding Compounds
Compounds are substances formed when two or more elements chemically combine in a fixed ratio. Here’s a detailed explanation of the characteristics of compounds, focusing on option D.
Fixed Composition
- Compounds have a definite chemical formula that represents the proportion of each element present. For example, water (H2O) always consists of two hydrogen atoms and one oxygen atom.
Unique Properties
- The properties of a compound are distinct from the properties of its constituent elements. For instance, sodium (a reactive metal) and chlorine (a toxic gas) combine to form sodium chloride (table salt), which is safe for consumption.
Reasons Other Options Are Incorrect
- Option A: Separation by Physical Means
- Compounds cannot be separated by physical means; they require chemical reactions for separation into their elements.
- Option B: Retaining Properties
- Compounds do not retain the individual properties of their elements. Instead, they exhibit new properties.
- Option C: Mixtures of Elements
- Compounds are not mixtures; they are pure substances formed from specific combinations of elements.
Conclusion
In summary, option D correctly identifies that a compound has a fixed composition and unique properties, distinguishing it from mixtures and individual elements. Understanding this helps in grasping the fundamental concepts of chemistry, especially in recognizing how compounds are formed and their significance in various chemical reactions.
Compounds are substances formed when two or more elements chemically combine in a fixed ratio. Here’s a detailed explanation of the characteristics of compounds, focusing on option D.
Fixed Composition
- Compounds have a definite chemical formula that represents the proportion of each element present. For example, water (H2O) always consists of two hydrogen atoms and one oxygen atom.
Unique Properties
- The properties of a compound are distinct from the properties of its constituent elements. For instance, sodium (a reactive metal) and chlorine (a toxic gas) combine to form sodium chloride (table salt), which is safe for consumption.
Reasons Other Options Are Incorrect
- Option A: Separation by Physical Means
- Compounds cannot be separated by physical means; they require chemical reactions for separation into their elements.
- Option B: Retaining Properties
- Compounds do not retain the individual properties of their elements. Instead, they exhibit new properties.
- Option C: Mixtures of Elements
- Compounds are not mixtures; they are pure substances formed from specific combinations of elements.
Conclusion
In summary, option D correctly identifies that a compound has a fixed composition and unique properties, distinguishing it from mixtures and individual elements. Understanding this helps in grasping the fundamental concepts of chemistry, especially in recognizing how compounds are formed and their significance in various chemical reactions.
What are pure substances?- a)Mixtures of different elements
- b)Substances that have been chemically altered
- c)Materials containing only one kind of particle
- d)Solutions of various compounds
Correct answer is option 'C'. Can you explain this answer?
What are pure substances?
a)
Mixtures of different elements
b)
Substances that have been chemically altered
c)
Materials containing only one kind of particle
d)
Solutions of various compounds
| | Nidhi Bhatt answered |
Pure substances are defined as materials that contain only one type of particle throughout their composition. This means they cannot be separated into other substances by physical methods. Examples include distilled water and pure metals like gold.
Which of the following is an example of a physical change?- a)Rusting of iron
- b)Burning of wood
- c)Cooking an egg
- d)Dissolving sugar in water
Correct answer is option 'D'. Can you explain this answer?
Which of the following is an example of a physical change?
a)
Rusting of iron
b)
Burning of wood
c)
Cooking an egg
d)
Dissolving sugar in water
| | Nidhi Bhatt answered |
Dissolving sugar in water is an example of a physical change because the sugar can be recovered by evaporating the water, and no new substances are formed. In contrast, burning wood and cooking an egg involve chemical changes.
What is the main component of Graphene Aerogel?- a)Hydrogen
- b)Silicon
- c)Carbon
- d)Oxygen
Correct answer is option 'C'. Can you explain this answer?
What is the main component of Graphene Aerogel?
a)
Hydrogen
b)
Silicon
c)
Carbon
d)
Oxygen
| | Nidhi Bhatt answered |
Graphene Aerogel is primarily made from carbon, which gives it unique properties such as being extremely lightweight and highly porous. This material is used in various applications, including environmental cleanup and energy-saving technologies.
What is matter?- a)Anything that has volume but no mass
- b)Materials that can be seen and touched
- c)Substances that are chemically reactive
- d)Everything that has mass and takes up space
Correct answer is option 'D'. Can you explain this answer?
What is matter?
a)
Anything that has volume but no mass
b)
Materials that can be seen and touched
c)
Substances that are chemically reactive
d)
Everything that has mass and takes up space
| | Nidhi Bhatt answered |
Matter is defined as anything that has mass and occupies space. This includes all physical substances, like solids, liquids, and gases. Understanding matter is fundamental to studying the physical world and its properties.
What type of mixture can be separated by physical means?- a)Heterogeneous mixture
- b)Element
- c)Homogeneous mixture
- d)Compound
Correct answer is option 'A'. Can you explain this answer?
What type of mixture can be separated by physical means?
a)
Heterogeneous mixture
b)
Element
c)
Homogeneous mixture
d)
Compound
| | EduRev Class 8 answered |
Heterogeneous mixtures can be separated by physical means because their components remain distinct and can be identified separately. For example, a mixture of sand and salt can be separated using water and filtration.
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