Lakhmir Singh & Manjit Kaur: Materials Metals And Non-Metals- 1 | Lakhmir Singh & Manjit Kaur Solutions: Class 8 Science PDF Download

Q.1. What is the general name of the elements whose properties are intermediate between those of metals and nonmetals?

The elements whose properties are intermediate between the properties of metals and nonmetals are called Metalloids. For example, Boron, Silicon and Germanium are metalloids. Heat and electricity can pass through metalloids but not as easily as in metals. Metalloids are also called semiconductors.

Q.2. Name one metals and one nonmetal which exist in liquid state at room temperature.

The metal which is liquid at room temperature is Mercury (Hg). Another metal called Gallium also exists as liquid at room temperature. Its melting point is very low and it changed into a liquid when touched.
The nonmetal which is liquid at room temperature is Bromine.

Q.3. Name the property;
(a) Which allows metals to be hammered into thin sheets.
(b) Which enables metals to be drawn into wires.

(a) The property of metals which allows metals to be hammered into thin sheets is called Malleability. Due this unique property, metals can be flattened into thin sheets by hammering and rolling.
(b) The property of metals which enables them to be drawn into wires is called Ductility. Due to this property metals can be stretched without breaking and drawn into thin wires. For example, Aluminum and copper are examples of highly ductile metals.

Q.4. Name two metals which are soft and can be easily cut with a knife.

The two metals which are soft and easily cut with a knife are Sodium and potassium. The freshly cut surface of these metals is shiny but it tarnishes quickly on contact with air. This is because these metals react with oxygen and water and becomes dull grey in colour.

Q.5. If a metal coin is dropped on hard floor, it produces a ringing sound. What is this property of metals known as?

The property of metals to produce sound is called Sonority. Metals produce ringing sound and are sonorous in nature.

Q.6. Name the property of iron metal due to which it can be hammered to make objects of different shapes such as an axe, a spade or a shovel.

The property by which iron metal can be hammered to make objects of different shapes such as axe, spade etc. is called Malleability. As a result of high malleability, iron can be flattened or beaten into thin sheets and desired objects can be made by using it. Pixlr@0518

Q.7. Name a non-metal which is very hard.

Diamond is the hardest non-metal. It is made of carbon atoms.

Q.8. Name a non-metal which is good conductor of electricity?

Carbon, in the form of Graphite is a good conductor of electricity. It conducts heat and electricity like a metal or a metalloid.

Q.9. State on chemical property which can be used to distinguish a metal from a non-metal.

The chemical property which can be used to distinguish between a metal and a nonmetal is the formation of positive ions by metals. Metals form positive ions whereas nonmetals form negative ions. As a result, oxides of metals are basic whereas the oxides of nonmetals are acidic in nature.

Q.10. How do metal oxides differ from non-metal oxides?

Metals react with oxygen to form metallic oxides. These metallic oxides are basic because they react with water to form bases. On the other hand, nonmetals react with oxygen to form nonmetallic oxides. These oxides differ from metallic oxides because they are acidic in nature. Nonmetallic oxides react with water to form acids.

Q.11. An element forms an oxide which is acidic in nature. State whether the element is a metal or a non-metal?

An element which forms oxide which is acidic in nature is a non-metal. This is because nonmetallic oxides react with water to form acids.

Q.12. An element forms an oxide which is basic in nature. State whether the element is a metal or a non- metal?

An element which forms oxide which is basic in nature is a metal. This is because metallic oxides are basic in nature and they react with water to form bases.

Q.13. Write a word equation for the reaction of magnesium with oxygen.

Metals react with oxygen in the air to produce metal oxides. For example, magnesium reacts with oxygen to produce magnesium oxide when it is heated in air:
Magnesium + oxygen → Magnesium oxide
It can also be written as:
Mg + O2 → 2MgO

Q.14. Iron metal reacts slowly with the oxygen and moisture of damp air to form rust. State whether the rust formed is acidic, basic or neutral.

Iron is metal. It reacts with oxygen to form rust. Rust is chemically known as iron oxide. Since, rust is a metal oxide, it will be basic in nature.

Q.15. Name the gas evolved when a metal reacts with water.

Metals react with water to produce hydrogen gas. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas.

Q.16. Name the gas evolved when a metal reacts with a dilute acid.

Metals react with dilute acids to form metallic salts and hydrogen gas. For example, zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.

Q.17. 
(A) Name one metal which reacts with dilute hydrochloric acid to produce hydrogen gas.

Sodium reacts vigorously with dilute hydrochloric acid because it is above hydrogen in the reactivity series of metals.

(B) Name one metal which does not react with dilute hydrochloric acid.

Copper does not react with dilute hydrochloric acid because it is below hydrogen in the reactivity series of metals.

Q.18. Which metal is more reactive: iron or zinc?

Zinc is more reactive than iron. Zinc is placed above iron in the reactivity series. For example, Zinc can displace iron from ferrous sulphate solution to form zinc sulphate and iron.

Q.19. Which metal is less reactive: copper or iron?

Copper is less reactive than iron. For example, if we put Iron nail into copper sulphate solution. Iron nail will displace copper from copper sulphate solution.

Q.20. Name any five objects used in our everyday life which are made of metals.

Following are the objects in our daily life which are made of metals:
Utensils – The utensils we use daily are made from copper, aluminum and iron.
Jewellery – The jewellery is made from gold and silver.
Electric wires – These are made from copper and aluminium.
Mercury- It is used in thermometers.
Table salt- Sodium is used in making table salt.

Q.21. Name two metals which are used for making cooking utensils and water boilers for factories.

Copper, aluminium and iron are used for making cooking utensils. Iron is used for making water boilers in factories.

Q.22. Name two metals which are used for making electric wires.

Copper and aluminium are used for making electric wires due to their high ductility.

Q.23. Name the metal which is used in making thermometers.

Mercury is used for making thermometers. It is liquid at room temperature and is a very good conductor of heat. Even a slightest change in temperature can be noted by using mercury.

Q.24. Which metal is used to galvanize iron to protect it from rusting?

Zinc is used to galvanize iron to protect it from rusting. In this process, a thin layer of zinc is coated on the surface of iron. Zinc acts as a barrier against corrosion so that iron does not come in contact with water or moisture in the air.

Q.25. Name the metal which is used to make thin foils for packaging medicines, chocolates, and food items, etc.

Aluminium is used to make thin foils for packaging medicines, chocolates and food items. This is because it provides a complete barrier to light, oxygen, moisture and bacteria.

Q.26. Name two metals which are used to make jewellery.

Gold and silver are used to make jewellery. This is because these metals are attractive due to their luster and rarity. These metals do not tarnish or react with air.

Q.27. Where is iron present in our body?

Iron is a very important component of haemoglobin in our body. Haemoglobin is the substance in red blood cells that carries oxygen from our lungs and transports it throughout our body.

Q.28. Name the non-metal which is essential for maintaining life and inhaled during breathing.

Oxygen is the nonmetal which is essential for maintaining life and is inhaled during breathing. Oxygen is brought into our lungs via breathing. It is then transported by red blood cells to the entire body to be used to produce energy.

Q.29. Name one non-metal used for making fertilizers.

Phosphorus is used in making fertilizers.

Q.30. Which non-metal is used in water purification process to make drinking water supply germ-free?

Chlorine is used in water purification process to make drinking water supply germ-free. Chlorine kills pathogens such as bacteria and viruses by breaking the chemical bonds in their molecules.