Metals and Non-Metals
These are metal and non-metal notes for class 10. We shall learn about the various concepts of metals and non-metals.
Physical Properties of Metals
One of the easiest ways to identify a metal and a non-metal is to compare their features and properties. The properties of metals are as follows :
- Metals usually have a shining surface. It is called metallic lustre.
- All metals except mercury exist as solids at room temperature
- Metals are generally hard, but their hardness varies from one metal to another
- Metals are malleable; that is, they can be beaten into thin sheets
- Metals can also be drawn into wires. This property is called ductility
- Metals are good conductors of heat. They have high melting points. Silver and copper are the best conductors of heat, while lead and mercury are poor conductors. But gallium and caesium are two metals that have very low melting points. Further, Alkali metals, which are lithium, sodium, and potassium, are soft and have low densities and low melting points
- Metals are also good conductors of electricity
- Metals produce basic oxides when dissolved in water
- Metals are sonorous and hence produce a sound when they are stricken
Physical Properties of Non-metals
As per metals and non-metals notes, some examples of non-metals include carbon, oxygen, hydrogen, etc. Non-metals are usually in solid or gaseous form, and an exception to this is bromine which is a non-metal and is present in a liquid state.
Some properties of certain non-metals are as follows:
- Iodine is the only non-metal which is lustrous
- Carbon exists in various forms, but it is a non-metal. Each form of carbon is called an allotrope of carbon. Some forms of carbon are diamond and graphite.
- Non-metals produce acidic oxides when dissolved in water
Chemical Properties of Metals
When Metals are burnt in the air:
Metals combine with oxygen to form metal oxides, which are usually basic in nature. This happens when they are heated in the air. Some metal oxides, such as aluminium oxide and zinc oxide, are both acidic and basic in nature. They are called amphoteric oxides because they react with both acids as well as basic to produce salts and water. Metal oxides are insoluble in water but some of these, such as sodium oxide and potassium oxide, dissolve in water to form alkalis.
As per metal and non-metals class 10 notes, all metals do not react with oxygen at the same rate. Some hyper-reactive metals, such as potassium and sodium are immersed in kerosene. Some metals, such as magnesium, aluminium, zinc, and lead, form a thin layer of oxide, and this layer prevents further oxidation.
When metals are put in water:
Metals react with water to produce metal oxides and hydrogen gas. Those metal oxides which are soluble form metal hydroxide. Potassium and sodium react violently with cold water, so the hydrogen gas formed immediately catches fire. Magnesium, on the other hand, does not react with cold water, but with hot water, it forms magnesium hydroxide and hydrogen. Aluminium, iron, and zinc do not react with cold or hot water but react with steam to produce metal oxide and hydrogen. Lead, copper, silver, and gold do not react with water.
When metals are exposed to acids:
Metals react with acids and produce salt and hydrogen gas.
Properties of Ionic Compounds
The properties of ionic compounds included in class 10 science chapter 3 notes are as follows:
- Physical nature: Ionic compounds are solid and are relatively hard in nature. But they are brittle and break into pieces when pressure is applied
- Melting and Boiling points: They have high melting and boiling points
- Solubility: Ionic compounds are soluble but only in water. Not soluble in other liquids such as kerosene, petrol, etc.
- Conductor of Electricity: Ionic compounds do not conduct electricity in the solid state but conduct electricity when melted.
Extraction of Metals
Metals that are at the bottom of the reactivity series are found in the free states on earth, such as gold, silver, copper, etc. Metals that are highly reactive and present at the top of the reactivity series and not found in nature as free elements. Moderately reactive metals are found on earth in the form of oxides, sulfides, or carbonates.
Ores of various metals are contaminated due to the presence of soil, sand, etc., and this is called gangue. Thus, these impurities must be removed before the metal is extracted from ores. Let us learn more about the extraction of metals in metals n non-metals class 10 notes.
Metals that are low on the reactivity series are found on earth in the form of oxides. The metals can be extracted from their oxides by heating. The metals in the middle of the activity series are present in the form of sulfides and carbonates. They can be extracted by first heating them to create metal oxides. This process is called calcination. Then these oxides are then reduced to metals using suitable reducing agents such as carbon or through displacement reactions. Metals that are highly reactive are obtained through the process of electrolytic reduction.
As seen above in class 10 chemistry chapter 3 notes, when metals are extracted, they may not be in their purest form. Refining of metals is required to remove impurities. Electrolytic refining is used wherein the impure metal is made the anode, and a thin strip of pure metal is made the cathode. The electrolyte used here is a solution of metal salt. On passing a current through the electrolyte, the impurities get separated from the metals. The impurities settle down at the bottom of the anode and are known as anode mud.
One of the most common instances of corrosion is when iron develops a brown flaky substance called rust when exposed to moist air for long periods of time. Silver articles turn black when exposed to air. This is because a silver sulfide coating is formed due to the presence of sulfur in the air. Similarly, copper reacts with moist carbon dioxide and develops a green coating. This coating is called copper carbonate.
Corrosion leads to the loss of quality of the metal and should be avoided. Some steps can be taken to prevent metals from getting corroded. With respect to iron, corrosion can be prevented by methods such as painting and galvanising. Galvanization is a method where a thin layer of zinc is applied as a coating on metals such as steel and iron to prevent rusting. Chrome plating, anodising, and making alloys can also prevent iron from corroding. Let us take a deeper look at alloys, a part of chapter 3 science class 10 notes.
Alloying not only prevents corrosion but also helps to improve the properties of the metals. Pure iron is very soft and stretches easily when heated, and this makes iron very difficult to work with. But when the iron is mixed with small amounts of carbon, it becomes strong and hard. Similarly, when iron is mixed with nickel and chromium, it becomes stainless steel. The properties of metals change when mixed with other substances. An alloy is a mixture of metal with other metals and non-metals. Alloys enable metals to be used for various purposes, which would not have been possible if the metal was in its purest form.