Physical Properties - Long Answer Questions
Medium Level (Application & Explanation)
Q1. Explain why metals are used for making electrical transmission wires, citing at least two physical properties.
Answer:
Metals like copper and aluminium are widely used to make electrical wires because they are excellent conductors of electricity. This means they let electricity pass through easily. Also, ductility allows these metals to be drawn into thin, long wires without breaking. Their combination of being ductile and having high electrical conductivity makes them ideal for safe and efficient power transmission.
Q2. Non-metals generally have low melting and boiling points. Give reasons for this characteristic and mention any exceptions.
Answer:
Most non-metals have weak forces between their molecules, so less energy is needed to melt or boil them. This is why many, like oxygen and sulphur, are gases or soft solids at room temperature. The exception is diamond (an allotrope of carbon), which has a very high melting point due to its strong covalent bonds forming a rigid structure. This unique bonding makes diamond extremely hard and heat-resistant.
Q3. Describe the physical properties that make gold and silver suitable for making jewelry.
Answer:
Gold and silver are beautiful metals because of their bright lustre (shine), attracting attention in ornaments. Both are highly malleable; they can be hammered into thin sheets and crafted into detailed designs. They are also ductile, allowing them to be drawn into fine wires for chains. Their resistance to corrosion keeps jewelry shiny and durable for years, adding further value in decorative use.
Q4. List and explain three exceptions to the general physical properties of metals and non-metals, supporting each with an example.
Answer:
First, diamond is an exception among non-metals; it is the hardest natural substance, unlike other soft non-metals. Second, sodium and potassium are metals but are so soft that they can be cut with a knife, while most metals are hard. Third, graphite (a non-metal) conducts electricity well, even though most non-metals do not. These exceptions are important for understanding the diversity within metals and non-metals.
Q5. Explain "malleability" and "ductility" in metals with examples and their practical importance.
Answer:
Malleability means a metal can be hammered into thin sheets without breaking. For example, gold leaf and aluminium foil are made this way. Ductility is the ability to draw out a metal into thin wires. Copper wires are common in houses because of their ductility. These properties are important because they allow metals to be shaped into useful items like wires, sheets, and foils used in construction, packaging, and electrical industries.
High Complexity (Analysis & Scenario-Based)
Q6. Imagine you need to design a container for storing acids in a chemical factory. Would you select a metal or a non-metal? Justify your answer with at least two properties from your syllabus content.
Answer:
A non-metal is better for storing acids. Most metals react with acids and may get corroded, leading to leaks and safety issues. Non-metals like carbon (in the form of graphite) or plastics (made mainly from non-metals) are generally not attacked by acids and are poor conductors of electricity, which prevents unwanted reactions. Their chemical stability and resistance make non-metals safer for storing acids.
Q7. Analyze why aluminium is used instead of iron for making aircraft bodies, based on the physical properties you have learned.
Answer:
Aluminium is used in aircraft because it is much lighter (low density) than iron, reducing the overall weight and increasing efficiency. It is also hard enough, malleable, and ductile, allowing it to be bent and shaped easily into various parts. Aluminium’s resistance to corrosion prevents it from rusting, which is essential for the safety and longevity of aircraft flying at high altitudes and in varied weather conditions.
Q8. A student says, “All metals are good conductors.” Do you agree? Explain your answer with at least one exception and describe the general trend.
Answer:
The statement is mostly true, as metals are generally good conductors of heat and electricity. However, there are exceptions. For example, mercury is much less conductive than copper or silver. Also, metals like tungsten conduct less compared to copper. So, not all metals conduct equally well, but most are better conductors compared to non-metals, which usually do not conduct at all (except graphite).
Q9. Compare the utility of metals and non-metals in daily life by analyzing their physical properties. Give one example each.
Answer:
Metals are used where strength, high melting point, and conductivity are needed. For example, iron is widely used in building bridges and structures because it is hard and strong. Non-metals are chosen where softness, lightness, or non-reactivity is essential. For instance, oxygen (a non-metal gas) is vital for breathing and life. Thus, the unique properties of each class determine their uses in technology, construction, medicine, and everyday tools.
Q10. If you are given samples of an unknown element and are asked to find out whether it is a metal or a non-metal using only physical properties, describe the steps you would follow and reasoning behind each.
Answer:
First, I would observe the appearance—if it is shiny, it might be a metal. Next, I would try to bend or hammer the sample; if it is malleable and doesn’t break, it is likely a metal, but if it breaks easily, it’s probably a non-metal. I would try drawing it into a wire to check for ductility. Then, I would check if the sample conducts electricity using a simple circuit. Finally, I’d note the sound when struck (sonorous or dull). Each test helps differentiate, since metals are generally shiny, malleable, ductile, good conductors, and sonorous, while non-metals are not.