Class 8 Science Chapter 4 MCQ for 2020-21
| Class: 8 | Science |
| Contents: | Multiple Choice Questions – MCQ Tests |
Class 8 Science Chapter 4 MCQ for Exams
Class 8 Science Chapter 4 MCQ tests are given below. Tests are divided in sets of 5 questions. After selecting the option you may see the correct answer and its explanation also. All the questions are confined to grade 8 science chapter 4 NCERT textbook only. To attend a new test, a Start a New Test, button is given at the end.
Q1
Boojho is writing some statements, choose the correct statement and help him:
[A]. If an element forms a basic oxide (which turns red litmus blue), then the element will be metal.
[B]. If an element forms an acidic oxide (which turns blue litmus red), then the element will be non-metal.
[C]. Carbon dioxide is acidic in nature.
[D]. All the above
Answer: Option D
Explanation:Here, all the above statements are correct. Hence, your answer will be option [D].
Q2
Paheli is writing some statement which is given by her teacher. Would you help him to choose the incorrect statements?
[A]. The mixture of “Copper Hydroxide” and “Copper Carbonate” which forms the green coating on copper.
[B]. Copper carbonate is basic in nature.
[C]. The formation of green coating of copper carbonate is also called “Corrosion of copper”.
[D]. Oxide of iron rust is not corrosion, it is a “Chemical reaction”.
Answer: Option D
Explanation:During the rusting of iron or iron metal combines slowly with the oxygen of air in the presence of water moisture to form a compound called “iron oxide”. This iron oxide is rust the reaction of iron metal with oxygen in the presence of water. Therefore, oxide of iron rust is corrosion, it is a “Chemical reaction”.
Q3
How do we get “Copper Hydroxide”?
[A]. When copper burns in air.
[B]. When copper reacts with hydrogen and oxygen.
[C]. When copper reacts with carbon dioxide.
[D]. When copper reacts with water, carbon dioxide and oxygen.
Answer: Option D
Explanation:When a copper object is exposed to moist air for a long time then copper reacts with water, carbon dioxide and oxygen present in moist air to form a green coating on the copper object. The green coating or green material is a mixture of copper hydroxide and copper carbonate which is formed by the action of moist air on copper object. The green coating of copper is also known as basic copper carbonate because it is basic in nature.
Q4
Metals generally react with dilute acids to produce hydrogen gas. Which of the following metals does not react with dilute hydrochloric acid:
[A]. Magnesium
[B]. Aluminum
[C]. Iron
[D]. Copper
Answer: Option D
Explanation:The less reactive metals like copper, silver and gold do not react with dilute hydrochloric acid to produce hydrogen gas.
Q5
Metals are generally hard. Which of the following metals is an exception and can be cut with a knife?
[A]. Iron
[B]. Sodium
[C]. Gold
[D]. Magnesium
Answer: Option B
Explanation:Metals are generally hard. This means that most of the metals cannot be cut easily. But sodium metal is soft and can be easily cut with a knife.
Q6
Which of the following statement is or are correct?
[A]. Solid non-metals are usually neither hard not strong.
[B]. Non-metals cannot be cut easily.
[C]. Non-metals have usually low melting point and high boiling points.
[D]. All the above.
Answer: Option A
Explanation:Non-metals can be cut easily. Non-metals have usually low melting point and low boiling points. Here, only option [A] is correct, as solid non-metals are usually neither hard not strong.
Q7
Paheli is writing some statements, choose the incorrect statements and help her:
[A]. Elements can be broken down by applying heat, light or electricity.
[B]. There are 92 naturally occurring elements known to us at present.
[C]. All the metals have similar properties.
[D]. The properties non-metals are opposite of metals.
Answer: Option A
Explanation:A substance which cannot be broken down into two or more simpler substances by chemical reaction by applying heat, by light or by electricity, is called an element. Therefore, here option [A] is incorrect.
Q8
The substance that will be flattened on beating with a hammer is:
[A]. Crystal of iodine
[B]. Lump of sulphur
[C]. Piece of coal
[D]. Zinc granules
Answer: Option D
Explanation:Metals can be beaten into thin sheets with a hammer. Non-metals break into small pieces when hammered. So, zinc granule will be flattened on beating with a hammer.
Q9
How do we get “Sulfuric Acid”?
[A]. When sulphur burns in acidic air.
[B]. When sulphur burns under acidic water.
[C]. When ash of sulphur dissolve in water.
[D]. When hydrogen and oxygen both reacts with sulphur.
Answer: Option C
Explanation:The product formed in the reaction of sulphur and oxygen is sulphur dioxide gas. When Sulphur dioxide is dissolved in water sulphurous acid is formed. The sulphurous acid turns blue litmus paper red. Generally, oxides of non-metals are acidic in nature.
Q10
Consider the following statements and choose the incorrect one:
[A]. Atom is the smallest part of an element.
[B]. An element is a substance which is made up of only one kind of atoms.
[C]. An atom of liquid sulphur or vapour forms of sulphur would be different as that of solid sulphur.
[D]. Oxygen and nitrogen are two examples of elements.
Answer: Option C
Explanation:A substance which cannot be broken down into two or more simpler substances by chemical reaction is called an element. The smallest particle of an element is called atom. An element is a substance which is made up of only one kind of atoms. The atoms of an element remain unaffected by the physical changes in the element. Thus, an atom of liquid sulphur or vapour forms of sulphur would be same as that of solid sulphur.
What is meant by lustre?
Metals generally shine brilliantly and can be highly polished. The electronic structure of metals is such that the metals are able to reflect incident light. This characteristic metallic feature is called lustre.
Why metals are called ductile?
Ability of the metals to be melted and drawn into thin wires is called ductility. Because of this property, metals are known as ductile.
What happened when metal react with dilute acids?
Most metals react with dilute acids (Sulphuric and hydrochloric acids) by replacing hydrogen and forming a salt. Hydrogen gas is released.
What is an alloy?
Alloy is a homogeneous mixture of two or more metals or of a metal and one or more non-metals
Physical Properties of Metals
| Physical State: | Metals are generally solids at room temperature. Mercury (Hg) is the only exception which is liquid at room temperature. |
| Malleability: | Metals can be spread by hammered or beaten into thin sheets, without breaking because metallic bonds in the metals do not break easily. Gold (Au), silver (Ag) are highly malleable elements. |
| Ductility: | Ability of the metals to be melted and drawn into thin wires is called ductility. |
| Lustre: | Metals generally shine brilliantly and can be highly polished. The electronic structure of metals is such that the metals are able to reflect incident light. This characteristic metallic feature is called lustre. |
| Conductor: | In metals, the bonds are formed by excess or free electrons moving around large array of atoms. These electrons are able to conduct electricity and heat. |
Density of Metals
Density of metals is high. Only sodium (Na) and potassium (K) have densities less than water. Thus all metals are hard meterials except sodium, potassium and lead which are soft metals.
