Class 8 Science Chapter 4 MCQ

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.

Color of the copper metal is not responsible for copper to be used as electrical conduction wires.

Sodium metal is very reactive. It reacts vigorously with oxygen and water. A lot of heat is generated in the reaction. It is, therefore, stored in kerosene.

Sulphur is a non-metal and it forms an acidic oxide i.e. Sulphur Dioxide (SO2), which turns blue litmus red.

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”.

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.

Aluminum reacts with hydrochloric acid as well as sodium hydroxide solution to produce hydrogen gas.

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”.

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.

The less reactive metals like copper, silver and gold do not react with dilute hydrochloric acid to produce hydrogen gas.

Here, all the statements are correct. Hence your answer will be option [D].

Mercury metal is in the liquid state at room temperature.

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.

Here, all the above statements are correct. Hence, your answer will be option [D].

Ductility is a characteristic property of metals. Sulphur is a non-metal, so it is not ductile. When stretched, sulphur break into pieces and do not form wires.

Most of the non-metals from acidic oxides but there are some exceptions. This is because some of the non-metals form neutral oxides which is neither acidic or basic. For example, hydrogen is a non-metal which forms a neutral oxide as H2O which is commonly known as water.

Piece of coal is a non-metal which broke into small pieces when hammered.

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.

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.

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.

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.

Copper, aluminum and iron are metals but sulphur is not a metal.

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.

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.

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.