The World of Metals and Non-metals

At Bindu's school, a brass plate is still struck with a small hammer to mark the end of each period. Bindu says it's made of metal because metals ring when they are struck. Govind says the material doesn't matter much — a wooden plate of exactly the same size would ring just as loudly if you hit it hard enough. Who is right?

Mrinal sets up an experiment: one iron nail in a dry, closed bottle; one in a bottle of boiled water with a layer of oil on top; and one in a little ordinary water, open to the air. Mrinal predicts that the nail completely under the boiled water and oil will rust the most, because rust is caused by water. Zubair says that nail will hardly rust at all. Whose prediction will come true?

The Diwali sweets at Smita's house are covered with a paper-thin layer of silver called varq. Smita says varq is real silver, beaten again and again until it becomes that thin. Mithun says that's impossible — no metal can be thinner than paper, so varq must be some kind of shiny paper. Whose reasoning holds up?

Arpita's family repaints their iron gate every two years. Arpita says the paint is only for looks — the gate stays strong because the iron is thick. Her neighbour Baldev points to a spot where the paint got scratched last year: the iron there has turned brown and is flaking, while the painted parts are fine. He says the paint is what protects the gate. Who is right?

In a circuit-testing activity, the bulb glows when Sukhmani places a pencil's 'lead' between the two wires. Sukhmani concludes that pencil lead must be a metal, since it conducts electricity. Lalit says pencil lead is actually graphite, a form of carbon, and carbon is a non-metal — one property alone can't decide it. Who is thinking like a scientist?

The teacher burns a strip of magnesium ribbon, which leaves a white powder. She dissolves the powder in a little water and asks the class what it will do to red litmus paper. Juhi predicts it will turn red litmus blue, because the powder comes from a metal. Pranjal says everything made by burning is acidic, like smoke, so the red litmus will stay red. Whose prediction is correct?