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Types of pure substances - class-VIII

Description: types of pure substances
Number of Questions: 19
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Tags: chemistry matter around us methods of separation is matter around us pure the nature of matter pure substances and mixtures: separation of mixtures composition of matter elements, compounds and mixtures structure of matter and molecule element, compound and mixture is matter pure
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In which of the following compounds resonance does not occur
(i) ${H _2}O$
(ii) $Si{O _2}$
(iii) $S{O _3}$
(iv) $C{O _2}$

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Both (i) and (iv)

  2. Both (i) and (ii)

  3. Both(iii) and (iv)

  4. (i),(ii)and(iv)

Show answer
Correct Option: D

Which of the following is/are example(s) of mixtures?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Air

  2. $Fe + S$

  3. Bronze

  4. All of the above

Show answer
Correct Option: D
Explanation:

Air is a mixture of gases. $Fe + S$ is also a mixture. Bronze is an alloy and all alloys are mixtures.

A compound is always ______ whereas a mixture is :

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Heterogenous, both heterogenous and homogenous

  2. Homogenous, heterogenous

  3. Homogenous, Both homogenous and heterogenous

  4. None of above

Show answer
Correct Option: C
Explanation:

Compound is made up of two or more pure substances which are always homogenous. Mixtures contains two or more pure substances physically combined which may be homogenous or heterogenous

Which of the following is a pure gas?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Ntural gas

  2. Water gas

  3. Laughing gas

  4. Coal gas

Show answer
Correct Option: C
Explanation:

Pure gas is not a mixture.


Natural gas consists of a mixture of gases like methane, higher alkanes, carbon dioxide etc. So it is not a pure gas.

Similarly, water gas is a mixture of $CO, H _2S$
Coal gas is a mixture of $H _2,CH _4,CO$
But laughing gas is only $N _2O$, So it is pure gas.


Hence, the correct option is $C$

Which of the following obey the law of constant proportions in their formation?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Mixtures

  2. Compounds

  3. Elements

  4. Colloids

Show answer
Correct Option: B
Explanation:

A compound always follow the law of constant proportions because in a compound the elements that are present are always in the constant ratio.

Among the following, which is\are the difference between compound and mixture?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. The constituents of a compound can be separated only by chemical methods.

    The constituents of a mixture can be separated easily by physical methods.

  2. Compounds are pure substances.

    Mixtures are impure substances.

  3. The constituents of a compound are present in a fixed ratio.

    The constituents of a mixture are present in varying ratios.

  4. All of above

Show answer
Correct Option: D
Explanation:

Compounds are pure substances whereas mixture are impure substances. The constituents of a compound can be separated only by chemical methods and that of a mixture can be separated easily by physical methods. The constituents of a compound are present in a fixed ratio.The constituents of a mixture are present in varying ratios.

_____is chemically mixed whereas____is physically combined.

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Element, compound

  2. Compound, mixture

  3. Mixture, compound

  4. Mixture, element

Show answer
Correct Option: B
Explanation:

Compound is made up of two or more elements that are chemically combined whereas mixtures are made up of two or more pure substances that are physically combined. 

Which of the following is not a property of mixtures?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Components of mixtures are present in a varying proportions

  2. They are always homogeneous

  3. The components of mixtures retain their original properties

  4. The components of mixtures can be separated by physical means

Show answer
Correct Option: B
Explanation:

Mixtures can be homogeneous or heterogeneous. Oil and Water is a heterogeneous mixture.

Which of the following methods can be used to separate hydrogen and oxygen in water?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Boiling

  2. Electrolysis

  3. Distillation

  4. None of the above

Show answer
Correct Option: B
Explanation:

Electrolysis decomposes the water into oxygen and hydrogen due to passage of electric current.

Each component of a ______ retains its individual properties.

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Compound

  2. Element

  3. Mixture

  4. Solute

Show answer
Correct Option: C
Explanation:

Matter that consists of two or more substances which may be elements, compounds or both mixed together physically in any proportion, but not chemically combined is called as a mixture. Each component of a mixture retains its individual properties. 

For example, we could mix various proportions of hydrogen and oxygen gas, as long as you do not ignite the mixture, the combination will form a mixture that can be separated.

Which of the following is not an example of compound?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Brass

  2. Air

  3. Bitumen

  4. All of the above

Show answer
Correct Option: D
Explanation:

Brass, Air and Bitumen are all mixtures. None of them are compounds.

Mixture is different from a compound. True or false?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

A mixture consists of two or more substances which may be elements, compounds or both mixed together physically in any proportion, but not chemically combined. However, a compound consists of two or more elements that are chemically combined in a fixed proportion. Hence, a compound is different from a mixture.

The components present in mixtures are in :

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. fixed proportion

  2. variable proportion

  3. Both A and B

  4. None of the above

Show answer
Correct Option: B
Explanation:

The components present in the mixture are in variable proportions.

Which of the following is not a property of mixture?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Does not have a sharp melting or boiling point

  2. Heat is taken in or given out in the preparation

  3. Can be separated by physical means

  4. May be homogeneous or heterogeneous

Show answer
Correct Option: B
Explanation:

The parts of a mixture can be separated by physical means. A mixture does not have a sharp melting or boiling point. It may be homogeneous or heterogeneous. Energy is neither given out nor absorbed in the preparation of a mixture. However, heat is taken in or given out in the preparation of a compound.

Which of the following statement is incorrect?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. In compounds components are present in definite proportion whereas in mixtures components are present in varying proportion

  2. Compounds are homogenous whereas mixtures are mostly heterogeneous

  3. Particles in a compound are generally of same kind whereas in mixtures they are of different kind

  4. None of the above

Show answer
Correct Option: D
Explanation:

All the compounds are made up of different elements and have properties different from their constituent element.

Mixture composed of variant proportion of components.
Hence, all statements are correct.

Which of the following is a characteristic property of both mixtures and compounds?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. Their properties are same as those of their components

  2. Energy is released when they are formed

  3. Their masses are equal to the sum of the masses of their components

  4. They contain the components in fixed proportions

Show answer
Correct Option: C
Explanation:

Mixture and a compound both follow the law of conservation of mass so their weight equals to the sum of mass of their components.

Ionic compounds have ____ melting and boiling points whereas covalent compounds have _____ melting and boiling point.

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. low, high

  2. moderate, low

  3. high, low

  4. moderate, high

Show answer
Correct Option: C

Which of the following can give further simplification using ordinary means?

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. An element or a mixture

  2. A mixture or a compound

  3. A mixture or an atom

  4. An element or a compound

Show answer
Correct Option: B
Explanation:

A mixture or a compound can give further simplification using ordinary means.


A mixture can be broken into individual components.

A compound can be broken into individual elements.

A substance composed of two or more compounds, each of which retains its own properties is called a mixture.

Hence option B is correct.

A commercial cake is :

chemistry pure substances and mixtures: separation of mixtures difference between mixtures and compounds pure substance and mixtures types of pure substances

  1. a molecule

  2. a mixture of compounds

  3. an isotope

  4. an isomer

  5. an acid salt

Show answer
Correct Option: B
Explanation:

A commercial cake is a mixture of compounds. 


Cake contains various compounds such as coco, butter, milk, cream etc.

Hence the correct option is B.

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