Question 1: Define an alloy and explain how it differs from a pure metal.

Answer: An alloy is a mixture of two or more metals (or a metal and a non-metal) that are fused together to produce a material with different properties from the individual metals. Unlike pure metals, alloys are not elements but mixtures designed to enhance specific properties.

Question 2: Describe the mechanism by which alloying improves the strength of a metal.

Answer: Alloying introduces different atoms into the metallic structure, which disrupts the regular arrangement of metal ions. This hinders the movement of dislocations, making the metal harder and stronger.

Question 1: What is the main component of stainless steel, and why is it added?

Answer: The main component of stainless steel is iron, with added chromium. Chromium is added to prevent rusting by forming a protective oxide layer.

Question 2: Which alloy is primarily used in making jewellery due to its gold content and durability?

Answer: Gold Alloy

Question 1: A sample of brass contains 70% copper and 30% zinc by mass. Calculate the mass of zinc in a 150 g sample.

Answer: Mass of zinc = (30/100) × 150 g = 45 g

Question 2: If an alloy has a density of 8.4 g/cm³ and a volume of 10 cm³, what is its mass?

Answer: Mass = density × volume = 8.4 g/cm³ × 10 cm³ = 84 g

Question 1: Describe a theoretical experiment to compare the corrosion resistance of stainless steel and pure iron. Include variables and safety precautions.

Answer: An experiment can be set up by exposing samples of stainless steel and pure iron to a corrosive solution, such as saltwater, for a fixed period. Variables include the type of metal (independent variable), exposure time, and solution concentration. Control variables include temperature and surface area. Safety precautions include wearing gloves, goggles, and working in a well-ventilated area to handle chemicals safely.

Question 2: Explain how alloys improve the properties of metals in industry, giving specific examples.

Answer: Alloys enhance properties such as strength, corrosion resistance, and durability. For example, stainless steel resists rust and is used in cutlery and medical instruments, while bronze, an alloy of copper and tin, is hard and used in statues and machinery parts.

Question 1: A new alloy is developed with 50% aluminium and 50% magnesium. Describe its potential uses based on its composition and properties.

Answer: This alloy, being lightweight and corrosion-resistant, could be used in aerospace or transportation industries to reduce weight while maintaining strength.

Question 2: A steel sample shows increased hardness after alloying with small amounts of carbon. Explain the scientific reason for this change.

Answer: Adding carbon creates interstitial atoms that hinder dislocation movement within the steel's crystal structure, making it harder and more resistant to deformation.

Question 1: Summarise the main advantages of using alloys over pure metals.

Answer: Alloys are generally stronger, more resistant to corrosion, and tailored to specific needs, making them more suitable for practical applications compared to pure metals.

Question 2: Explain how the concept of metallic bonding relates to the properties observed in alloys.

Answer: Metallic bonding involves a 'sea' of delocalised electrons that hold metal ions together. In alloys, the presence of different metal atoms disrupts this electron sea, leading to altered properties such as increased strength and resistance, due to the modified bonding environment.