y8 end of year exam Flashcards
How is acid rain formed and what are it’s problems?
Factories burn fuels with sulphur and carbon in them. When these fuels are burnt they mix with oxygen to create CO2 and O2, acidic gases. These gases reach the sky, where they mix with rainwater. This rain pollutes rivers, kills wildlife and erodes stone-work.
How do you make oxygen?
hydrogen peroxide = (using manganese oxide as a catalyst) water + O2
How do you get metal and non metal oxides?
MetaALs form ALkaline oxides, when mixed with oxygen, but non-metals for acidic oxides when mixed with oxygen.
How do you make CO2?
calcium carbonate + acid = salt + water + CO2 OR
metal carbonate + heat = CO2 + metal oxide (thermal decomposition)
What do you get if you mix sulphur, carbon dioxide and metals with oxygen?
Carbon + oxygen = carbon dioxide
sulphur + oxygen = sulphur dioxide
metal + oxygen = metal oxide e.g.
magnesium + oxygen = magnesium oxide
What are the tests for oxygen, hydrogen and carbon dioxide?
oxygen: relights a burning splint
carbon dioxide: turns limewater cloudy
hydrogen lighted wooden splint makes a popping sound in a tube of hydrogen
What is the composition of air?
78% nitrogen, 21% oxygen, 1% argon, water vapour, CO2, traces of other gases.
What was the past composition of air and why has it changed?
The early atmosphere was mostly carbon dioxide, with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane.
The proportion of oxygen went up because of photosynthesis by plants. The proportion of carbon dioxide went down because it was locked up in sedimentary rocks such as limestone, and in fossil fuels, it was absorbed by plants for photosynthesis, it dissolved in the oceans. The burning of fossil fuels is adding carbon dioxide to the atmosphere faster than it can be removed. This means that the level of carbon dioxide in the atmosphere is increasing.
What is global warming and why is it caused?
Carbon dioxide is a greenhouse gas. It absorbs heat energy and prevents it escaping into space. This keeps the Earth warm enough for living things to exist on it. Greenhouse gases are not a bad thing in themselves. But too much of them in the atmosphere leads to global warming, where the average temperature of the Earth rises quickly. The level of CO2 in the atmosphere has been rising because we are burning fossil fuels.
What happens when acids react with metals?
acid + metal = salt + hydrogen
What does a catalyst do?
Prove the reaction with an alternate pathway with a lower activation energy
