Published by: BhumiRaj Timalsina
Published Date: 02 Feb 2022
Until now, about 118 elements have been found. On the basis of their properties, they have been divided into 3 groups or categories. They are metal, non-metal and metalloid. Some elements are hard, shiny and good conductor of electricity. These types of elements are called metal. Some examples are iron, copper, gold, silver, aluminum etc. Some elements are soft, non-shiny and bad conductor of electricity. These types of elements are called non-metal. Some examples are sulphur, oxygen, nitrogen etc. Some elements have the properties of both metal and non-metal. This type of elements are known as metalloid. Some examples are: silicon, arcenic etc. Human beings have been using metals for many years. We use it to make different containers, plates etc. Likewise, we have been using gold and silver as jewellery. We also use metals in the form of iron in the process of making house. Therefore, metals hold a great importance in our daily life. It is also essential for the development of the country. The country which has more use of metal, that country is regarded to be advanced. Most of the metals are found in the form of mixture in nature. Some metals like gold and silver are found in the pure form in nature.
General properties of metals. The matter which is hard in the solid form but can be made thin and long by beating is known as metal. Iron, copper, gold etc are metals. Every metal has its own properties but some properties are same for every metal. We will discuss about some properties of the metal in this chapter.
Pure metal is shiny.
Collect iron, copper, aluminium, etc. Clean them with water, cloth or paper. Now, put them on the top of a paper. Observe their surface. Do they shine or not? They reflect the light rays, that is why they shine.
Metals are mostly hard in touch. But this hardness differs from metal to metal. Some metals like sodium, potassium etc are not hard. Hard metals cannot be easily cut. Activity 2 Take the pieces of copper, zinc, brick and wood. Now, scratch them with a metal nail one by one. Which piece can be scratched easily? Observe it. It is hard to scratch copper and zinc as they are metal. While it is easy to scratch brick and wood. This is how we know that metals are hard.
When metal hit other substance or hit each other then it produces sound.
Take a big piece of any metal like iron or copper and tie it up with the help of a string. Now, hit it with the help of a rod. It produces tinkling sound. The molecules in the metal are strongly packed with each other. And so it produces sound. Sound is produced by the vibration of bodies.
Most of the metals are made thin by using a hammer. This property of metal is known as malleability. Activity 4 Take a piece of metal or aluminum. Look at the breadth of it. Now hit it with a hammer and check if there is increase in its breadth or not. When we hit the metal with a hammer there is increase in its breadth and it became thin. It proves that metals can be made thin by beating or they are mallable.
When we heat the gold, silver, copper etc and beat, it becomes longer and thin. This property of metal is known as ductility. One gram of gold can be made into two kilometer long thread. This property of the gold can be used to make Jewellery.
Electricity can flow easily through metals. Electricity is supplied in our houses by using the wire made from coppor and aluminum.
Take two dry cell, one long aluminum wire and one bulb. Now make an electric circuit as shown in the figure. Now put a metal coin in the middle of the wire and press it. Watch if the bulb lights up or not. The bulb lights up. Thus, we can conclude that metal is a good conductor of electricity.
Heat can be easily transferred through the metals. Due to this property of metal, we use metal pots for cooking our food. Iron rod wooden rod
Take a metal rod and another wooden rod. Put them closer to a burning candle. After sometimes, what change will occur in both of them? The metal rod gets heated from one end to the other while as the heat does not transfer from the wooden rod. Thus, we can prove that metal is a good conductor of heat.
Usually, metals are found in the solid state. But some metals are in liquid state in normal temperature and pressure. For example: mercury
Uses of metals
Metals are used in our daily life as well as in different industries.
Metals are used:
1. To make different utensils.
2. To make different weapons.
3. To make the electric wire.
4. To make house, bridge, bus, train etc.
5. To make ornaments.
6. To make coins.
7. Aluminum foil is used to wrap up the medicines, chocolate, etc for the safety.
8. Mercury is used in thermometer to measure temperature.
Non metals are obtained in solid, liquid and gas states in nature. But they cannot be beaten into thin plate and thread like structure. For example: carbon, sulphur, phosphorus etc. Non-metals have their own properties. However, some properties are in common. Some common properties are mentioned here:
1. Non-metals are found in solid, liquid and gaseous state.
2. Non-metals are comparatively softer than the metal.
3. Non-metals do not produce tinkling sound.
4. Non-metals do not possess lusture.
5. Non-metals cannot be pulled to thread like structure.
6. Non-metals cannot be beaten into thin plate like structure.
7. Non-metals are bad conductor of heat and electricity.
Uses of non-metals
1. Non-metals are used as insulator.
2. Non-metals are used to fill up the balloons.
3. Non-metals are used as fuels in the rocket.
4. Non-metals like sulphur is used to make explosives.
Iron is brownish in colour. Freshly cut iron posses lusture. Rust can be formed easily on iron. Iron is used to make steel. Iron has greater importance in our daily life. Iron is used to make houses, bridges, bus, car, train, etc and different utensils as well.
Copper is red, brown in colour. It is good conductor of electricity. So, it is used to make electrical equipment. It is also a good conductor of heat. So, utensils are also made from copper. Brass is made from the mixture of copper and zinc.
Gold is bright and yellowish in colour. It is not affected from air and water. So, it shines. It is used to make different ornaments. It is also used to make statue of gods and goddesses. It is one of the expensive metal.
Silver is a white and shiny metal. Water and air do not have any effect on it. It is a good conductor of electricity than others. It is used in electric devices. It is also used to make Jewellery. It is also used to fill in the teeth.