Exam, Class-8th, Sci., Chap. 7, Metals and Nonmetals

Q1. Fill in the blanks.

1. Most of the metals have up to ... electrons in their outermost shell.  
2. Sodium and potassium are soft and can be easily cut by a...  
3. Pure gold is ... carat gold.  
4. Elements such as arsenic, silicon, and germanium that have properties intermediate between metals and nonmetals are called...  
5. Graphite, an allotrope of carbon, is a very good conductor of...  

Q2. State whether true or false.

1. Metals are generally good conductors of heat and electricity.  
2. Nonmetals are ductile and malleable.  
3. Sodium metal is kept immersed in kerosene.  
4. Gold and silver are known as noble metals because they react very rapidly with dilute acids.  
5. The oxides of nonmetals are acidic in nature.  

Q3. Match the following.

Group 'A' (Element / Substance)       Group 'B' (Property / Characteristic)

1. Sodium (\text{Na})                     a. Liquid metal at room temperature

2. Mercury (\text{Hg})                  b. Soft metal that can be cut with a knife

3. Diamond                                    c. Yellow coloured solid nonmetal

4. Sulphur                                      d. Hardest natural substance

Q4. Write the answer in one sentence.

1. What is meant by ductility?  
2. Define an alloy.  
3. Name two metals that remain in a liquid state at room temperature.  
4. What type of ions are formed when metal atoms lose their valence electrons?  

Q5. Write a difference (distinguish between).

Metals and Nonmetals.  

Q6. Write uses.

1. Uses of Noble Metals (Gold, Silver, Platinum):
2. Uses of Nonmetals.

Q7. Give Scientific Reasons.

1. Sodium metal is kept in kerosene.  
2. Stainless steel vessels in the kitchen often have a copper coating on the bottom.  
3. Copper and brass vessels are cleaned with lemon.  

Q8. Answer the following questions.

1. What methods are used to prevent the corrosion of metals?  
2. Explain what happens when metals react with oxygen, with the help of a general word equation.