Class 08 Basic sciences Metal and non Metal
A. Answer these Questions
1. Name ten metals?
Answer: Ten examples of metals are potassium (K), iron (Fe), platinum (Pt), tin (Sn), copper (Cu), calcium (Ca), sodium (Na), magnesium (Mg), mercury (Hg) and silver (Ag).
2. Metals have a high tensile strength. Explain also give one example of how this property of metals is used?
Answer:
Metals have a high tensile strength due to their metallic bonding, which allows them to withstand pulling forces without breaking.
Example: Steel cables are used in suspension bridges to support the weight of the bridge and traffic.
3. Why cant you
(a) draw wires from a piece of wood or coal
(b) use nylon or jute ropes for electrical transmission
(c) use a cooking utensil made of cardboard
Answer: (a) We cannot draw wires from a piece of wood or coal because they are brittle. They break down on stretching.
(b) We cannot use nylon or jute ropes for electrical transmission because they are bad conductors of electricity.
(c) We cannot use a cooking utensil made of cardboard because it is a bad conductor of heat and it will start burning itself if kept on fire.
4. Name the five non metal found in gaseous form?
Answer: Hydrogen (H), nitrogen (N), oxygen (O), chlorine (Cl) and argon (Ar) are five nonmetals that are gaseous at room temperature
5. Name two metals react vigorously with cold water. Name one metal which,if ignited continue to burn in steam?
Answer: Potassium and sodium are two metals that react vigorously with cold water.
Magnesium is a metal that continues to burn in steam, if it is ignited.
6. Mention three uses of oxygen.
Answer: Three uses of oxygen:
(a) It is required in all combustion processes.
(b) It is used in the productions of nitric acid and sulphuric acid.
(c) It is used in extraction of metals from their ores.
7. Mention three uses of nitrogen?
Answer: Three uses of nitrogen:
(a) It is used by plants for making proteins.
(b) It is used in manufacturing ammonia and urea.
(c) It is used for filling food packets.
8. Define an alloy?
Answer: An alloy is a homogenous mixture of metals or metals and nonmetals.
B. Answer these Questions
1. Mention five physical properties of metals.
Answer :
Five physical characteristics of metals are:
(a) They have a high tensile strength; therefore, they cannot be broken down easily.
(b) They are malleable; i.e., they can be beaten into thin sheets.
(c) They are ductile; i.e., they can be stretched into thin wires.
(d) They are good conductors of heat.
(e) They are good conductors of electricity.
2. What are the physical properties of nonmetals ?
Answer: Physical properties of nonmetal are :
- Nonmetals lack metallic properties
- They are usually found on the right side of the periodic table
- Nonmetals are usually gases or brittle solids
- They have low melting and boiling points
3. Name a non metal which When redhot reacts with steam.What happen as a result of the reaction
Answer: Carbon is a nonmetal. When it is redhot, it reacts with steam. This reaction forms a gaseous mixture of carbon monoxide and hydrogen, called water gas. The following reaction occurs:
C (red hot) + O2 --------------> (water gas)
4. Mention three uses of metals, giving reason?
Answer : Three uses of metals are:
(a) Iron is used for making tools, machines and agricultural equipment because it is very strong, tough and cheap.
(b) Aluminium is malleable so Aluminium foil is used to pack food and medicines.
(c) Mercury is a good conductor of heat and does not stick to glass. Thus, it is used in thermometers.
5. Describe the uses of carbon?
Answer: Uses of carbon:
(a) Graphite is used in making pencils.
(b) Diamond is used as a gem and for cutting glass and rocks.
(c) Graphite is a good conductor of electricity. Thus, it is used as an electrode.
C. Answer these Questions
1. How would you use the activity series while studying the displacement of hydrogen from acids by metal?
Answer: Activity series is an ordered arrangement of metals and hydrogen (nonmetal) with respect to their activities.
The reactivity of a metal decreases top to bottom in the activity series.
For example : Metals that are placed above hydrogen in the activity series can displace hydrogen from dilute hydrochloric acid and sulphuric acid.
Metals that are placed below hydrogen in the activity series cannot displace hydrogen from acids.
2 NA + 2HCl ------------------> 2NaCl + H2
Cu + HCl ------------------> No reaction
2. Describe an activity to show that the lead of pencil is good conductors of electricity but sulpher doesnot.
Answer:
Following activity shows that the lead of a pencil conducts electricity and sulphur does not.
Take a pencil and sharpen both its ends. Connect the ends of the pencil to an electric circuit, formed by connecting a bulb to the cell. The bulb glows when pencil is connected to it. This shows that the lead of a pencil conducts electricity. This occurs because lead contains graphite, which is a good conductor of electricity.
Now, replace the pencil with a piece of sulphur. The bulb will stop glowing. This shows that sulphur does not conduct electricity.
D. Complete sentence:
1. Graphite and iodine are lustrous nonmetals.
2. All metals are good conductors of heat and electricity.
3. The socalled lead (black part) of a pencil is made of clay and graphite.
4. Though a metal, mercury is a liquid at ordinary temperatures.
5. Argon is used for filling electrical bulbs.
6. Liquid nitrogen is used to preserve donated organs.
E.Choose the correct options
1. (d) bromine
Bromine is a nonmetal that is liquid at ordinary temperatures.
2. (d) All of these
All the given options are solid nonme
3. Answer :
(a) silver
Silver is the best conductor of electricity.
4. (d) all of these
5. (d) neon
F. Match the coloumn
Answer :
Substance Property 1 Property 2
1. Neon A. Metal p. Ductile
B, s B. Nonmetal q. Malleable
2. Graphite C. Solid r. Kills germs
B, C, u D. Liquid s.Nonreactive
3. Iodine t. Cuts glass
B, C, r u. Conducts electricity
4. Aluminium
A, C, p, q, u
5. Diamond
B, C, t
6. Mercury
A, D, s
No comments:
Post a Comment