What is solder used for?
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Welding electrical wires together.
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What is solder used for?
Welding electrical wires together.
How long of a wire can be drawn from one gram of gold?
About 2 km.
What property allows metals to be beaten into thin sheets?
Malleability.
What happens when metals are burnt in air?
Almost all metals combine with oxygen to form metal oxides.
What is the significance of the oxide layer formed on metals?
It protects the metal from further oxidation.
Define the term 'Gangue'.
The worthless material that surrounds or is mixed with the valuable mineral in an ore.
Does sodium chloride (NaCl) exist as molecules?
No, it exists as aggregates of oppositely charged ions.
What can reactive metals do in relation to less reactive metals?
Reactive metals can displace less reactive metals from their compounds in solution or molten form.
What happens when you cut metals like iron, copper, and aluminum?
They can be cut with a sharp knife, indicating their malleability.
What was observed regarding the rate of bubble formation in the activity?
Magnesium produced bubbles the fastest.
Which metals are known to be the most malleable?
Gold and silver.
What is the reaction equation for copper burning in air?
2Cu + O2 → 2CuO (Copper + Oxygen → Copper(II) oxide)
Which metals do not react with oxygen even at high temperatures?
Silver and gold.
Which two metals have very low melting points and can melt on your palm?
Gallium and caesium.
Why are potassium and sodium kept immersed in kerosene oil?
To protect them and prevent accidental fires due to their vigorous reaction with oxygen.
What happens to the surfaces of metals like magnesium, aluminium, and zinc at ordinary temperatures?
They are covered with a thin layer of oxide that prevents further oxidation.
Define the term 'Ore'.
A type of rock that contains sufficient minerals with important elements including metals that can be extracted for economic gain.
What is the position of potassium in the reactivity series?
Potassium is the most reactive metal.
What is a notable exception regarding the physical state of metals at room temperature?
All metals except mercury exist as solids.
How can elements be classified?
As metals or non-metals based on their properties.
Why are school bells made of metals?
Because metals are sonorous and produce sound when struck.
What should you be cautious about when handling sodium metal?
Always handle sodium metal with care due to its reactivity.
What states of matter do non-metals exist in?
Non-metals can be solids or gases, except bromine which is a liquid.
In which solvents are ionic compounds generally soluble?
Ionic compounds are generally soluble in water but insoluble in solvents like kerosene and petrol.
What is the reaction of iron with steam?
3Fe + 4H2O → Fe3O4 + 4H2.
Which metal is the least reactive according to the activity series?
Gold is the least reactive metal.
What happens when copper wire is placed in iron sulfate solution?
No reaction occurs; copper does not displace iron.
What is an alloy?
An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal.
What happens to iron nails in test tube A?
They rust due to exposure to both air and water.
How is copper extracted from its ore Cu2S?
By heating in air.
What happens during the roasting of zinc ores?
2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2(g).
What are the cation and anion present in MgCl2?
Cation: Magnesium (Mg²⁺); Anion: Chloride (Cl⁻).
What is the general form of a displacement reaction?
Metal A + Salt solution of B → Salt solution of A + Metal B.
What is the reactivity series?
A list of metals arranged in the order of their decreasing activities.
What is the order of reactivity of metals with dilute hydrochloric acid?
Mg > Al > Zn > Fe.
What is the ability of metals to be drawn into thin wires called?
Ductility.
How do ionic compounds conduct electricity?
Ionic compounds conduct electricity in solution or molten state due to the movement of ions; they do not conduct electricity in solid state.
What happens when calcium reacts with water?
Ca + 2H2O → Ca(OH)2 + H2.
What does the reactivity series help to understand?
It helps to understand the relative reactivities of different metals.
What is the significance of malleability and ductility in metals?
They allow metals to be given different shapes according to our needs.
What element is likely to react with oxygen to give a compound with a high melting point and is soluble in water?
Calcium.
Which metals are commonly found in the free state?
Gold, silver, platinum, and copper.
What are amphoteric oxides?
Oxides like aluminium oxide and zinc oxide that show properties of both basic and acidic oxides.
Which metals are comparatively poor conductors of heat?
Lead and mercury.
What gas is produced when dilute hydrochloric acid is added to a reactive metal?
Hydrogen gas (H2).
What is calcination?
The process of converting carbonate ores into oxides by heating strongly in limited air.
What happens when sodium and chlorine react?
Sodium loses an electron, which is taken up by chlorine.
What is the physical state of common ionic compounds like sodium chloride?
They are typically solid at room temperature.
Why do ionic compounds have high melting and boiling points?
Because a considerable amount of energy is required to break the strong inter-ionic attraction.
Why is sodium kept immersed in kerosene oil?
To prevent it from reacting with moisture and oxygen in the air.
What type of bond forms between sodium and chloride ions?
Strong electrostatic forces of attraction.
What do metals produce when they react with water?
A metal oxide and hydrogen gas.
What are the melting and boiling points of MgCl2?
Melting point: 981 K; Boiling point: 1685 K.
What happens during the anodising process?
A clean aluminium article is made the anode and electrolysed with dilute sulphuric acid to form a thicker protective oxide layer.
What conditions are necessary for iron to rust?
Presence of both air and water.
What is cinnabar and how is it processed to obtain mercury?
Cinnabar (HgS) is an ore of mercury that is heated to form mercuric oxide (HgO), which is then reduced to mercury.
What alkalis are formed when sodium oxide and potassium oxide dissolve in water?
Sodium hydroxide (NaOH) and potassium hydroxide (KOH).
What is roasting in the context of metal extraction?
The process of converting metal sulphides into oxides by heating strongly in the presence of excess air.
What is produced when a metal reacts with dilute acid?
Salt and hydrogen gas.
What charge does a chlorine atom acquire after gaining an electron?
A unit negative charge, forming a chloride anion (Cl⁻).
Define the term 'Mineral'.
A naturally occurring substance that is solid and stable at room temperature, represented by a chemical formula.
Which allotrope of carbon is the hardest natural substance?
Diamond.
What metals are suggested for the activities?
Iron, copper, aluminum, magnesium, sodium, lead, and zinc.
What can be inferred about the nature of ionic compounds based on conductivity tests?
Ionic compounds conduct electricity when dissolved in water.
Which pair will give a displacement reaction: NaCl solution and copper metal?
No, it will not give a displacement reaction.
What chemical process is used for obtaining a metal from its oxide?
Reduction.
Which metals react violently with cold water?
Potassium and sodium.
What happens to most metal oxides in water?
Most metal oxides are insoluble in water, but some dissolve to form alkalis.
What should be done to determine the reactivity of metals with water?
Put small pieces of metals in beakers with cold water and hot water, and observe their reactions.
Why do iron nails not rust in test tube B?
Because there is no air dissolved in the boiled distilled water.
Which metals are the best conductors of heat?
Silver and copper.
What is the action of gas evolved from heated sulphur powder on dry litmus paper?
It does not change color.
Why are many metal ores oxides?
Because oxygen is a very reactive and abundant element on Earth.
What type of oxides are formed when non-metals combine with oxygen?
Acidic oxides.
What is the physical nature of ionic compounds?
Ionic compounds are solids, somewhat hard, and brittle due to strong forces of attraction between positive and negative ions.
How do non-metals form negatively charged ions?
By gaining electrons when reacting with metals.
What happens when manganese dioxide is heated with aluminium powder?
It produces manganese, aluminium oxide, and heat.
What property of graphite allows it to conduct electricity?
It has a structure that allows free movement of electrons.
What is aqua regia and what can it dissolve?
A mixture of concentrated hydrochloric acid and nitric acid that can dissolve gold and platinum.
What are amphoteric oxides?
Metal oxides that react with both acids and bases to produce salts and water.
What are the characteristics of metals?
Metals are lustrous, malleable, ductile, and good conductors of heat and electricity. They are solids at room temperature, except mercury which is a liquid.
What is the electronic configuration of chlorine after it becomes a chloride ion?
2, 8, 8.
What occurs during the reaction of sodium with water?
The evolved hydrogen immediately catches fire due to the violent exothermic reaction.
How does the reactivity series of metals relate to metal extraction?
The reactivity series helps in understanding how a metal is extracted from its ore, with less reactive metals often found in a free state.
What type of reaction is the thermit reaction?
Highly exothermic.
Arrange metals A, B, C, and D in order of decreasing reactivity.
B > A > D > C.
What is the balanced chemical equation for the reaction of sulphur with oxygen?
S + O2 → SO2.
Why are platinum, gold, and silver used to make jewellery?
They are non-reactive and do not tarnish easily.
How does the electrical conductivity of an alloy compare to that of pure metals?
The electrical conductivity and melting point of an alloy is less than that of pure metals.
What is the basis for determining if a reaction has occurred in a displacement reaction?
If metal A displaces metal B from its solution, it is more reactive than B.
What is the purpose of displacement reactions in metallurgy?
They can displace metals of lower reactivity from their compounds.
What is the thermit reaction used for?
To join railway tracks or cracked machine parts.
What is the electronic configuration of chlorine (Cl)?
2, 8, 7.
Why does hydrogen gas not evolve when a metal reacts with nitric acid?
Because nitric acid is a strong oxidizing agent that oxidizes H2 to water.
Which metal is the most ductile?
Gold.
What are ores?
Ores are minerals that contain a high percentage of a particular metal and can be profitably extracted.
How can elements be classified as metals and non-metals?
Based on their chemical properties.
How can metals low in the activity series be extracted?
By heating their oxides alone.
What do metals generally exhibit in terms of hardness?
Metals are generally hard, but hardness varies from metal to metal.
What is the reaction when iron reacts with dilute H2SO4?
Fe + H2SO4 → FeSO4 + H2.
What are impurities in ores called?
Gangue.
What does 22 carat gold consist of?
22 parts of pure gold and 2 parts of either copper or silver.
Why are electric wires coated with PVC or rubber-like materials?
To provide insulation and prevent electric shocks.
What happens when metals strike a hard surface?
They produce a sound and are said to be sonorous.
What is metallic lustre?
The shining surface of metals in their pure state.
What are ionic compounds formed by?
The transfer of electrons from a metal to a non-metal.
Which metals should not be used in the activity due to their vigorous reaction with water?
Sodium and potassium.
What is unique about iodine as a non-metal?
Iodine is lustrous.
What are some examples of non-metals?
Carbon, sulphur, iodine, oxygen, hydrogen.
What are different forms of carbon called?
Allotropes.
What is the electronic configuration of sodium (Na)?
2, 8, 1.
What happens when ionic compounds are heated?
They may impart color to the flame and can melt.
What is the significance of physical properties in categorizing elements?
Physical properties help in determining the uses of metals and non-metals.
Which metal is more reactive according to the observations in Activity 3.12, copper or iron?
Iron is more reactive than copper.
What types of oxides do non-metals form?
Acidic or neutral oxides.
Are ionic compounds soluble in water?
Yes, many ionic compounds are soluble in water.
What indicates that a metal is a good conductor of electricity?
The bulb glows when the metal is placed in an electric circuit.
Why can't metals high up in the reactivity series be reduced by carbon?
They have more affinity for oxygen than carbon.
Do non-metals displace hydrogen from dilute acids?
No, they do not displace hydrogen; they react with hydrogen to form hydrides.
What is formed when aluminium burns in air?
Aluminium oxide (Al2O3).
Name two metals found in nature in the free state.
Gold and Platinum.
How are sodium, magnesium, and calcium obtained?
By electrolytic reduction of their molten chlorides.
What is anodising?
A process of forming a thick oxide layer on aluminium to improve its resistance to corrosion.
What general physical properties can be observed for metals and non-metals?
Hardness, malleability, ductility, conductivity, and sonority.
What is the basis for separating gangue from ore?
Differences between the physical or chemical properties of the gangue and the ore.
What is the electronic configuration of magnesium (Mg)?
2, 8, 2.
Which method is suitable for preventing an iron frying pan from rusting?
All of the above (applying grease, paint, or a coating of zinc).
How does aluminium oxide react with hydrochloric acid?
Al2O3 + 6HCl → 2AlCl3 + 3H2O.
What happens when an iron nail is placed in copper sulfate solution?
Iron displaces copper, resulting in a reaction.
Which metal is observed to be the most reactive in the experiments?
Sodium.
What are minerals?
Minerals are elements or compounds that occur naturally in the earth's crust.
What are alkali metals known for in terms of physical properties?
They are soft and can be cut with a knife, have low densities and low melting points.
What happens to soluble metal oxides when they dissolve in water?
They form metal hydroxide.
What is the major source of metals?
The earth's crust is the major source of metals.
What is the reason metals react to attain a stable electronic configuration?
Metals tend to lose electrons to achieve a completely filled valence shell.
What is produced at the anode during the electrolysis of sodium chloride?
Chlorine gas.
How does calcium react with water compared to potassium and sodium?
Calcium's reaction is less violent and does not produce enough heat for hydrogen to catch fire.
What would you observe if metal B is added to a solution of Copper(II) sulphate?
A displacement reaction occurs, resulting in the formation of copper.
What should students wear during the burning activity?
Eye protection.
What type of ores are metals in the middle of the activity series mainly found as?
Oxides, sulphides, or carbonates.
What do metals like lead, copper, silver, and gold do in relation to water?
They do not react with water at all.
What are the three categories of metals based on reactivity?
Metals of low reactivity, medium reactivity, and high reactivity.
What is the process of electrolytic refining?
The impure metal is made the anode, and pure metal is made the cathode in an electrolyte solution.
What type of oxides do most non-metals produce when dissolved in water?
Acidic oxides.
Why are food cans coated with tin and not zinc?
Because zinc is more reactive than tin.
What is corrosion?
The phenomenon where the surface of some metals, such as iron, is corroded when exposed to moist air for a long period of time.
In the electrolytic refining of a metal M, what are the anode, cathode, and electrolyte?
Anode: impure metal M, Cathode: pure metal M, Electrolyte: a solution of metal salt.
Which metals are never found in nature as free elements due to their high reactivity?
K, Na, Ca, Mg, and Al.
Which metals do not react with cold or hot water?
Aluminium, iron, and zinc.
What is the chemical reaction that takes place when zinc reacts with iron(II) sulphate?
Zn + FeSO4 → ZnSO4 + Fe.
How is zinc oxide reduced to metallic zinc?
By heating with carbon: ZnO(s) + C(s) → Zn(s) + CO(g).
Why is aluminium used to make utensils for cooking despite being highly reactive?
It forms a protective oxide layer that prevents further reaction.
What happens when potassium reacts with water?
2K + 2H2O → 2KOH + H2.
What is deposited at the cathode during the electrolysis of copper sulfate?
Pure copper.
What are the combined states in which copper and silver can be found?
As their sulphide or oxide ores.
What happens to magnesium when it reacts with hot water?
It forms magnesium hydroxide and hydrogen, and starts floating due to hydrogen bubbles sticking to its surface.
Name two metals that will displace hydrogen from dilute acids.
Zinc and magnesium.
What is rust?
A brown flaky substance formed when iron reacts with moist air.
What do metals produce when they react with acids?
A salt and hydrogen gas.
What type of oxides do most metals produce when dissolved in water?
Basic oxides.
What observation can be made about metals when heated?
Metals are good conductors of heat and have high melting points.
What is the outcome of metals reacting with steam?
Some metals may react with steam while others do not.
What is the activity series?
A list of common metals arranged in order of their decreasing reactivity.
What happens in a displacement reaction?
A more reactive metal displaces a less reactive metal from its salt solution.
What type of solution did the man use to clean the gold bangles?
A strong acid, likely hydrochloric acid, which can dissolve impurities but also gold.
What is metallurgy?
The extraction of metals from their ores and then refining them for use.
What is the chemical reaction for obtaining mercury from cinnabar?
2HgS(s) + 3O2(g) → 2HgO(s) + 2SO2(g) followed by 2HgO(s) → 2Hg(l) + O2(g).
What are amphoteric oxides?
Oxides that can react with both acids and bases.
What is the action of gas evolved from heated sulphur powder on moist litmus paper?
It turns red, indicating acidity.
What is the chemical reaction for the calcination of zinc carbonate?
ZnCO3(s) → ZnO(s) + CO2(g).
Why are sodium, potassium, and lithium stored under oil?
To prevent them from reacting with moisture and oxygen in the air.
What is galvanisation?
A method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
What happens to iron when mixed with a small amount of carbon?
It becomes hard and strong.
What is an alloy?
A homogeneous mixture of two or more metals, or a metal and a non-metal.
Which metal is the most reactive among A, B, C, and D?
Metal B (based on the displacement reactions).
What color flame is observed when magnesium burns in air?
A dazzling white flame.
Why do iron nails not rust in test tube C?
Because the air is dry, preventing moisture.
Name two metals that will not displace hydrogen from dilute acids.
Copper and silver.
Which metals can displace hydrogen from dilute acids?
Metals above hydrogen in the Activity series.
What is the first step in the extraction of metals from ores?
Enrichment of ores by removing impurities called gangue.
Why are sour substances like lemon or tamarind juice effective in cleaning tarnished copper vessels?
They contain acids that react with the tarnish (copper oxide) to remove it.
How can the rusting of iron be prevented?
By painting, oiling, greasing, galvanising, chrome plating, anodising, or making alloys.
What are two ways to prevent the rusting of iron?
Why is pure gold not suitable for making jewelry?
Because it is very soft.
Why are carbonate and sulphide ores converted into oxides during extraction?
Oxides are easier to reduce to obtain the metal.
What are brass and bronze examples of?
Brass is an alloy of copper and zinc, and bronze is an alloy of copper and tin.
What is the significance of the iron pillar at Delhi?
It was built over 1600 years ago and is known for its rust resistance.
What would you observe when zinc is added to a solution of iron(II) sulphate?
A displacement reaction occurs, resulting in the formation of zinc sulfate and iron.
What are the properties of non-metals?
Non-metals are neither malleable nor ductile and are bad conductors of heat and electricity, except for graphite.
What is pure gold known as?
24 carat gold.
What carat gold is generally used in India for making ornaments?
22 carat gold.
What is an amalgam?
An alloy where one of the metals is mercury.
What is the purpose of removing gangue from ores?
To extract pure metal from the ore.
Differentiate between metals and non-metals based on their chemical properties.
Metals tend to lose electrons and form cations, while non-metals tend to gain electrons and form anions.
Why is copper used to make hot water tanks instead of steel?
Copper has better thermal conductivity and is less prone to corrosion than steel.
What is stainless steel made from?
Iron mixed with nickel and chromium.
