Properties and Reactions of Metals

Properties of Metals

• Metals generally have high melting and boiling points.
• Metals are good conductors of heat and electricity.
• Metals are usually malleable (can be hammered into sheets) and ductile (can be drawn into wires).
• Metals tend to be lustrous (shiny).
• Different metals have different strengths and densities.

Reactivity Series of Metals

• The reactivity series shows the order in which metals react with other substances.
• A more reactive metal will displace a less reactive metal from its compound.
• The most reactive metals are at the top of the series, and the least reactive are at the bottom.
• Example metals in the reactivity series include potassium, sodium, magnesium, iron, copper, and silver.
• Knowing a metal's position in the reactivity series helps predict its reactions with acids and other substances.

Reactions of Metals with Acids

• Metals react with acids to produce a salt and hydrogen gas.
• The reaction is more vigorous with more reactive metals.
• The type of salt produced depends on the metal and the acid.
• The equation for a general reaction is: Metal + Acid → Salt + Hydrogen
• Examples of reactions include magnesium reacting with hydrochloric acid producing magnesium chloride.
• Observing bubbles of gas often indicates that a reaction has taken place.

Observations in Metal Acid Reactions

• A visible change in the metal is sometimes observed.
• The metal may dissolve or disappear during the reaction.
• Production of hydrogen gas bubbles is a key observation in these reactions.
• The temperature of the reaction mixture may increase, signifying that heat is released.
• The solution's appearance may change (color) due to the presence of the new salt.

Factors Affecting Metal Reactions

• The reactivity of the metal. More reactive metals react more vigorously.
• The concentration of the acid. Higher concentrations usually lead to faster reactions.
• The temperature. Higher temperatures can speed up the rate of reaction.
• The surface area of the metal. A larger surface area provides more area for reaction.

Uses of Metals

• Different metals have specific properties that make them useful for various applications.
• Iron is used in construction and making tools due to its strength.
• Copper is used in electrical wiring due to its conductivity.
• Aluminium is used in food packaging due to its lightweight properties.
• Metals are often combined to create alloys, which have improved properties compared to the individual metals.

Acids

• Acids are substances that release hydrogen ions (H+) when dissolved in water.
• Acids have a sour taste and can corrode some materials.
• Common examples include hydrochloric acid, sulfuric acid, and nitric acid.
• Acid strength differs based on the amount of hydrogen ions released which can be measured using a pH scale.
• Acids are important in many chemical reactions and industrial processes.

Identifying Acids

• Litmus paper turns red in the presence of acid.
• Universal indicator displays different colours depending on the acid concentration.

Neutralisation Reactions

• An acid reacts with a base to form a salt and water.
• This reaction is known as neutralisation.
• The reaction often results in a decrease in acidity or basicity.
• The pH of the resultant solution will be near 7 (neutral).
• Neutralisation reactions are widely used in various applications.

Common Bases

• Bases release hydroxide ions (OH-) when dissolved in water.
• Bases often feel slippery and can be corrosive like bleach (sodium hypochlorite) or drain unblocker (sodium hydroxide).
• Common bases include sodium hydroxide and potassium hydroxide.