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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.

1. Detergents should not be strong, they may spoil the texture, colour of delicate garments.

2. Now a days many detergents are available especially for woollen, delicate clothes.

3. They should not contain bleach, phosphorous which will harm delicate clothes.

1. A molecule of a detergent holds on to a water molecule at one end and an oil molecule at the other.

2. As a result the molecules of oil mix with the water.

3. This is how detergent acts on our soiled clothes. So detergent removes any oil or dirt sticking on to our clothes. 

4. Due to the property of holding on to both oil and water, soap water spreads easily on many types of surfaces. 

5. This property of spreading on a surface is called surface activity. 

6. Detergents are surface active. 

7. One effect of surface activity is lather formation.

Iodine is used to make purple coloured solution which is applied on cuts and wounds as an antiseptic. It is used in the treatment and prevention of wound infection.

1. Soap is a man-made detergent which has been in use since ancient times.

2. It was prepared by using animal fat and wood ash. In hard water, soap does not give lather, it loses its cleansing property. 

3. So we can not use soap in hard water. Now synthetic detergents have taken the place of soap. 

4. They can be used in hard water as well 

5. Synthetic detergents have many more advanced properties like they are added with perfumes, conditioner for fabric, etc.

1. Detergent which is made by processing naturally available material, soap is a manmade detergent which has been in use since ancient times. 

2. In those days soap was prepared by using animal fat and wood ash. 

3. Therefore two types of soap (a) Hard Soap is used for washing clothes. It is a sodium salt of fatty acids, (b) Softsoap is used for bathing. It is a potassium salt of fatty acids. 

4. It does not cause irritation of the skin. 

5. But we can’t use soap in hard water because soap does not give lather but forms a scum. So, soap loses its cleansing property so now synthetic detergent have taken the place of soap. 

6. Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes. These can be used in hard water as well.

1. Curry stains stick fast to the criss-crossing threads of the material of our clothes.

2. Curry contains turmeric a natural indicator which turns red in a basic solution. 

3. Soaps are sodium salts of fatty acids and are basic in nature. 

4. While washing the clothes, turmeric reacts with soap solution and turns red forming red spots on the clothes. 

5. But the spots disappear after washing the clothes with plenty of water.

1. It is naturally available soap nut (ritha) and soap pod (shikekai) are the natural detergents in common use. 

2. They contain a chemical named saponin. 

3. Soap nut and soap pod do not have any harmful effect on human skin or on silk, woollen threads, and cloth.

Now a days we use variety of toothpastes and tooth powders to clean our teeth.

1. Concrete is prepared by mixing cement, water, sand and gravel. 

2. For making a strong and leak proof slab certain substances are mixed in concrete. 

3. Now a days, roads are made of concrete because they are very durable, strong and smooth.

1. Masheri is the smokeless form of tobacco. It is tobacco, containing teeth cleaning powder 

2. It contains tobacco leaves. 

3. Tobacco contains toxic and Carcinogenic chemicals which can cause cancer, oral cancer, mouth and throat cancer, gum disease, tooth decay. 

4. Its use can cause abnormal delivery in pregnant women.

Two types of soap are:

1. Hard soap is used for washing clothes. It is a sodium salt of fatty acids.

2. (a) Softsoap is used for bathing. It is a potassium salt of fatty acids, (b) It does not cause irritation of the skin, (c) But we can’t use soap in hard water because soap does not give lather but forms a scum, (d) So, soap loses its cleansing property so now synthetic detergents have taken place of soap, (e) Synthetic detergents are obtained by subjecting these raw materials (fats and kerosene) to a variety of chemical processes, (f) These can be used in hard water as well.

The correct answer is Filtration.

i. Surfactant

ii. Saponin

iii. Fluoride

iv. Detergere

v. Portland cement

vi. Concrete

vii. Soap nut

1) Mixture

2) handpicking

3) Sublimation

The Right option is : (c) sulphur 

We cannot hold hot metal pan directly because metals are good conductor of heat and they hurt us. So we use plastic or wooden handle to hold the hot metal pan because plastic and wood are bad conductor of heat and they do not hurt us.

Connecting wires are made up of copper and aluminium because these metals are ductile and good conductor of electricity.

Iron, Copper and Aluminium are metals because these are hard and lustrous but Sulphur, Nitrogen and Oxygen are non-metals.

The Right option is (b) sodium

(c) aluminium

(a) Copper metal is used for making electric wires because it is highly ductile in nature. It is a good conductor of electricity.

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. Metals have free electrons which makes them good conductors of heat and electricity.

(b) Graphite is a good conductor of electricity. Graphite is made of carbon. Its valence electrons are free to move. As a result, graphite is able to conduct electricity which makes it useful for making electrode in a cell.

(c) Immersion rods for heating liquids are made of metallic substances because metallic substances are good conductors of electricity and heat. Metals have free electrons which makes them good conductors of heat and electricity.

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

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

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.

Phosphorus is used in making fertilizers.

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.

Metals are sonorous because they produce a unique sound when something hard strikes their surface. As a result, metals are used in making bells or gongs.

1. The materials which do not change shape are solids.

Example: 

Wood, rock, brick, plastic objects, vegetables … etc. 

2. The materials which change shape are liquids. 

Example: 

Water, rasam, milk, kerosene, oil… etc.

1. Many materials change their state from solid to liquid and from liquid to gas. 

2. Ghee at slightly low temperature will be in solid state. 

3. If it is heated it comes to liquid state and on further heating it becomes vapour.

Another example:

1. At room temperature candle wax will be in solid state (candle). 

2. When it is lighted it starts burning and liquid wax is seen at the wick of the candle. 

3. The white smoke on the top of the wick is wax vapour.

A) Solids:

1. Solids have a definite shape. 

2. Solids are incompressible. 

3. Solids do not flow.

B) Liquids:

1. Liquids occupy the shape of the container. 

2. Liquids are incompressible. 

3. Liquids can flow.

C) Gases:

1. Gases have no fixed shape. 

2. Gases can be compressible. 

3. Gases flow and diffuse.

1. Belt and 

2. shoes.

Stones are separated by handpicking from rice and pulses.

Pencil lead is made up of graphite.

Metals are sonorous. Sonorous means metals make noise on striking with another metal. So bells used in temples are made up of metals and not of wood which is a non-metal.

Bromine is a liquid non-metal.

The mud water filtered after using the filter paper is clean.

1. Before administering injections to patients, doctors mix injection powder with some liquid. 

2. This liquid is water and it is known as distilled water.

C. copper 

Copper cannot displace iron from iron sulphate solution because copper is less reactive than iron.

B. calcium 

Calcium is the most reactive metal than copper, iron and magnesium. It lies above all of these metals in reactivity series.

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.

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.

D. copper 

Copper corrodes by oxidation in which it reacts with oxygen in the air to form copper oxide. Copper oxide then combines with carbon dioxide to make copper carbonate, which gives it a green colour. This process is called corrosion of copper.

B. potassium 

Potassium reacts with water to potassium hydroxide and hydrogen gas. The reaction potassium with water is highly exothermic in nature. It produces a lot of heat energy and this heat energy can cause the hydrogen gas produced during the reaction, to catch fire. In order to keep it safe potassium is stored in kerosene.

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.

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

Metals are the elements which lose electrons to form cations and are electropositive in nature. For example, Sodium, potassium, Iron, Zinc and Calcium are metals. Metals are good conductors of heat and electricity. Metals are highly malleable and ductile.

Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. 

For example: chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. Nonmetals are not malleable and ductile but they are brittle. Nonmetals are bad conductors of heat and electricity. They have low melting and boiling points and are soft. 

Following are the difference in chemical properties between metals and nonmetals.

Metals are the elements which lose electrons to form cations and are electropositive in nature. 

For example: Sodium, potassium, Iron, Zinc and Calcium are metals. 

Following are characteristics of metals:

1. Metals are good conductors of heat and electricity. 

2. Metals are highly malleable and ductile. 

3. They have very high melting and boiling points. 

4. Metal oxides are basic in nature. 

5. Metals displace hydrogen from dilute acids.

Nonmetals: Nonmetals are the elements that gain electrons and form negative ions. They are also called electronegative elements. 

For example: chlorine, sulphur, oxygen, bromine, phosphorus and nitrogen are nonmetals. 

Following are the characteristics of nonmetals:

1. Nonmetals are not malleable and ductile but they are brittle. 

2. They are bad conductors of heat and electricity. 

3. They have low melting and boiling points and are soft. 

4. They form acidic or neutral oxides when they react with oxygen. 

5. Nonmetals do not displace hydrogen with dilute acids.

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