Year 10 Science · Unit 2 · Lesson 1
Challenge Worksheet
Learning Goals
Evaluate the claim
Someone claims...
"Burning a log destroys matter, the wood disappears and turns into nothing. After a campfire, there's almost no ash left compared to the original log, which proves that burning destroys the wood. The law of conservation of mass doesn't really apply to burning because fire is so intense it obliterates the fuel."
(a) What part of this claim is supported by what you can observe? (Be specific, do not just say "it's all wrong".)
(b) What is scientifically misleading or wrong about this claim? Use the law of conservation of mass and the concept of products to explain where the "missing" wood actually goes.
(c) What evidence or extra information would you need to definitively prove to a sceptic that mass is conserved when wood burns? Describe a practical method.
1. Photosynthesis in Australian eucalyptus trees converts carbon dioxide and water into glucose and oxygen. Explain how the law of conservation of mass applies to this reaction, even though the products are completely different substances from the reactants.
2. At Port Kembla, BlueScope Steel converts iron ore and coke into steel through chemical reactions. If 1000 kg of iron ore and 300 kg of coke are fed into a blast furnace and 200 kg of carbon dioxide gas escapes, predict the maximum possible mass of steel that could be collected. Explain your reasoning using conservation of mass.
Wrap Up
In one sentence, what was the main idea of this lesson?