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
Paheli is writing some statements. She wants to know in which of the following statements is or are incorrect?
[A]. Can iron will displace copper from copper sulphate solution.
[B]. Can copper will displace iron from iron sulphate solution.
[C]. Can zinc will displace copper from copper sulphate solution.
[D]. Can zinc will displace iron from iron sulphate solution.
Answer: Option B
Explanation:No, can copper will displace iron from iron sulphate solution. In a chemical reaction when a more reactive metal displaces the less reactive metal from its salt solution it is called, “displacement reaction” e.g. zinc can displace copper from its copper sulphate solution as zinc is more reactive than copper. Less reactive metal cannot displace the more reactive metal from its salt solution e.g. copper cannot displace zinc from its solution zinc sulphate is copper is less reactive than zinc.
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
Paheli appeared in class test where she wrote some statements but she confused to know the incorrect statement. Would you help her to know that?
[A]. The basic metal oxides turn red litmus to blue.
[B]. Metals react with oxygen to form metals oxides.
[C]. Metals oxides are basic in nature.
[D]. Ash of magnesium which forms an acidic oxide on burning in air.
Answer: Option D
Explanation:When magnesium burns in air it combines with oxygen of air to form magnesium oxide (which is a basic oxide). Magnesium oxide dissolves in water to form magnesium hydroxide solution. Magnesium hydroxide turns red litmus. It is a base and that magnesium oxide is a basic oxide.
Q4
Consider the following statements and choose the correct one:
[A]. Metals have high tensile strength.
[B]. Sodium and potassium are those non-metals which have low tensile strength.
[C]. Sodium and Sulphur (non-metal) are so soft that is can be cut with a knife.
[D]. All the above.
Answer: Option A
Explanation:Metals are usually strong; they have high tensile strength. This means that metals can hold large weights without snapping or without breaking. As iron metal in the form of steel is a very strong and having a high tensile strength. Due to this, iron metal is used in the construction of bridges, building, railway lines, machines, vehicles etc. Rest of all are incorrect.
Q5
Boojho appeared in class test where he wrote some statements but he confused to know the incorrect statement. Would you help him to know that?
[A]. Non-metals have low density which means they are light-weight.
[B]. Non-metals are not sonorous.
[C]. Non-metals, mercury can be found liquid in room temperature.
[D]. Non-metals can be solid liquid or gaseous at room temperature.
Answer: Option C
Explanation:Mercury is the only metal which is found in liquid state at room temperature.
Q6
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].
Q7
Mohan is writing some statements, choose the incorrect statements and help him:
[A]. Metals have high melting points and low boiling points.
[B]. Metals have high density which means they are heavy.
[C]. Metals are sonorous.
[D]. Sodium and potassium are examples of metals.
Answer: Option A
Explanation:Metals have high melting points and high boiling points. Rest of all are correct.
Q8
Consider the following statements and choose the incorrect one:
[A]. Malleable means which can be beaten (may be broken down) by a hammer to form thin sheets.
[B]. Ductile means which can be stretched or drawn to form thin wires.
[C]. Brittle means which breaks into pieces on hammering or stretching.
[D]. Lustrous means shiny.
Answer: Option A
Explanation:The property which allows the metals to be hammered into thin sheets is called malleability. Malleability is an important characteristic property of metals. Remember, malleable means which can be beaten (without broken down) by a hammer to form thin sheets.
Q9
Boojho appeared in class test where he wrote some statements but he confused to know the correct statement. Would you help him to know that?
[A]. Metals are good conductors of electricity but poor conductors of heat.
[B]. Some metals react with sodium hydroxide to produce hydrogen gas.
[C]. When metals react with acid, they form oxygen gas.
[D]. The non-metallic oxides turn red litmus into blue.
Answer: Option B
Explanation:Some metal reacts with base to form salts and hydrogen gas. Aluminum is a metal and sodium hydroxide is a base. When aluminum is heated with sodium hydroxide solution then sodium aluminate (salt) and hydrogen gas are formed. Zinc metal also reacts with sodium hydroxide solution to form hydrogen gas. Although, aluminum and zinc are the two common metals which react with base (like sodium hydroxide) to produce hydrogen gas. In general, we can say that some metals react with “Sodium Hydroxide” to produce hydrogen gas. But all the metals do not react with bases like “Sodium Hydroxide” to produce hydrogen gas.
Q10
Which of the following is not a metal?
[A]. Copper
[B]. Sulphur
[C]. Aluminum
[D]. Iron
Answer: Option B
Explanation:Copper, aluminum and iron are metals but sulphur is not a metal.
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.
