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ScienceClass 8ICSE

Name the man-made fibre prepared from natural materials.

The man-made fibre prepared from natural materials is rayon.

ScienceClass 8ICSE

Name the units of which cellulose polymer is made.

Cellulose is made up of repeating units of monomer glucose.

ScienceClass 8ICSE

Consider the following elements: Sodium, Sulphur, Carbon, Magnesium Which of these elements will form: (a) acidic oxides. (b) Basic oxides.

. Answer Acidic oxides: Carbon and Nonmetals react with oxygen to form nonmetallic oxides. Basic oxides: Sodium and Metals react with oxygen to form metallic oxides.

ScienceClass 8ICSE

The screwdriver used by an electrician has a plastic or wooden handle. Why?

Answer The screwdriver used by the electrician has a plastic or a wooden handle because the front portion of the screwdriver is made up of iron which is a good conductor of heat and electricity, so to prevent electric shock the handles are made of nonmetals such wood and plastic as they are insulator

ScienceClass 8ICSE

Element A is soft, brittle, and does not conduct electricity. Element B is hard, malleable, and 'ductile; and also conducts electricity. Which of the two elements, A or B, is a non-metal?

Answer Element A is non-metal as it is soft and brittle. Also mentioned it does not conduct electricity. Element B is metal as it is malleable and ductile. Also mentioned it conducts electricity.

ScienceClass 8ICSE

What type of oxides are formed: (a) when metals combine with oxygen? (b) when non-metals combine with oxygen?

Answer Metals react with oxygen to form metallic Nonmetals react with oxygen to form nonmetallic

ScienceClass 8ICSE

What is the nature (acidic/basic) of the following oxides? (a) Magnesium oxide (b) Sulphur dioxide Given the reason for your choice.

Answer Magnesium is a metal. Metals react with oxygen to form metallic oxides. Hence, Magnesium oxides are basic in nature. 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. Therefore, Sulphur dioxide is acidic in nature. Magnesium oxide is basic in nature.

ScienceClass 8ICSE

Can you hold a hot metallic pan which is without a plastic or a wooden handle? Give the reason for your answer.

Answer We can hold a hot metallic pan with wooden handle as wood is a poor conductor of heat and will not cause damage to the person holding it.

ScienceClass 8ICSE

Consider the following materials: Copper, Sulphur, Phosphorus, Carbon (such as pencil lead), Gold, Silver: Which of these materials are: Malleable and ductile; and brittle.

Answer Malleable and ductile: Copper, Gold and silver Brittle: Sulphur, Phosphorus and Carbon

ScienceClass 8ICSE

There are two boxes, one made of metal and the other made of wood, which are similar in appearance. How will you find out which box is made of metal?

Answer The box can be hit hard and the box which produces sonorous sound is considered as the metal box. This means that metals make a ringing sound when we strike them. The property by virtue of which metals make a ringing sound is called sonority.

ScienceClass 8ICSE

State any two physical properties for believing that aluminum is a metal.

Answer Aluminum is highly ductile and malleable. It can easily be drawn into wires and drawn into sheets.

ScienceClass 8ICSE

What is meant by saying that metals are: (i) Malleable (ii) Ductile (iii) Lustrous and (i) Sonorous

Answer i) Malleable: This means that metals can be beaten into thin sheets with a The property which allows the metals to be hammered into thin sheets is called malleability. Aluminum metal can be hammered to form aluminum foils. Ductile: This means that metals can be drawn (or stretched) into thin The property which allows the metals to be drawn into thin wires is called ductility. Copper metal can be drawn into thin copper wires (used as electric wires). Lustrous: This means that metals have a shiny The shiny appearance of the metals is called metallic luster. Gold metal is used for making jewelry because of its shiny luster. Sonorous: This means that metals make a ringing sound when we strike The property by virtue of which metals make a ringing sound is called sonority. Metal sheets are used for making bicycle bells and temple bells.

ScienceClass 8ICSE

Define (a) malleability, and (b) ductility.

Answer The property of metals that allows metals to be hammered into thin sheets is called Malleability. Non-metals do not possess this property. The property of metals which enables them to be drawn into wires is called Non-metals do not possess this property.

ScienceClass 8ICSE

Give a reason why. (a) Copper metals used for making electric wires. (b) Graphite is used for making electrodes in a cell. (c) Immersion rods for heating liquids are made of metallic substances.

Answer Copper metal is used for making electric wires because it is highly ductile in It is a good conductor of electricity. Graphite is made of Its valence electrons are free to move. As a result, graphite is able to conduct electricity which makes it useful for making an electrode in a cell. Immersion rods for heating liquids are made of metallic substances because metallic substances are good conductors of electricity and heat.

ScienceClass 8ICSE

Compare the properties of metals and nonmetals with respect to: (i) malleability (ii) ductility and (iii) conduction of heat and electricity

Answer The property of metals that allows metals to be hammered into thin sheets is called Non- metals do not possess this property. The property of metals which enables them to be drawn into wires is called Non-metals do not possess this property. Metals have free electrons which makes them good conductors of heat and Non- metals do not have free electrons, hence, they are nonconductors of heat and electricity.

ScienceClass 8ICSE

Which non-metals is used as a fuel?

Answer The non-metal carbon is used as fuel in the form of coal or charcoal.

ScienceClass 8ICSE

Name the gas produced when aluminum foil reacts with: (a) dilute hydrochloric acid. (b) Sodium Hydroxide solution.

Answer When aluminum foil reacts with sodium hydroxide, sodium aluminate is formed. Metals react with dilute acids to form metallic salts and hydrogen gas. For example, Aluminium foil reacts with dilute hydrochloric acid to produce aluminum chloride and hydrogen gas. The balanced chemical equation for the reaction is:

ScienceClass 8ICSE

State two physical properties on the basis of which metals can be distinguished from non-metals.

Malleability and ductility are the two physical properties on the basis of which metals can be distinguished from non-metals.

ScienceClass 8ICSE

Fill in the following blanks with suitable words (a) Metals are conductors of heat and (b) Most non-metals are conductors of heat and electricity. (c) Phosphorous is a very Non-metal. (d) Metals react with acids to produce gas. (e) Iron is more than copper. (f) Metals form oxides whereas non-metals form oxide. (g) Sulphur forms………oxide whereas magnesium forms oxide. (h) A non-metal is used to make an antiseptic solution called tincture

Answer Metals are good conductors of heat and electricity Most non-metals are poor conductors of heat and Phosphorous is a very reactive Non- Metals react with acids to produce hydrogen Iron is more reactivethan Metals form basic oxides whereas non-metals form acidic Sulphur forms acidic oxide whereas magnesium forms basic A non-metal is used to make an antiseptic solution called tincture iodine.

ScienceClass 8ICSE

Name two non-metals which are used in fireworks (crackers, etc.)

Answer Sulfur and sodium are the two non-metals used in fireworks.

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