C1.7 Changes in the Earth and its atmopshere

The Earth and its atmosphere provide everything we need. The Earth has a layered structure.
The surface of the Earth and its atmosphere have changed since the Earth was formed and are still changing.
The atmosphere has been much the same for the last 200 million years and provides the conditions needed for life on Earth.  Recently human activities have resulted in further changes in the atmosphere. There is more than one theory about how life was formed.

Candidates should use their skills, knowledge and understanding to:

recognise that the Earth’s crust, the atmosphere and the oceans are the only source of minerals and other resources that humans need

explain why scientists cannot accurately predict when earthquakes and volcanic eruptions will occur

explain and evaluate theories of the changes that have occurred and are occurring in the Earth’s atmosphere
Candidates should be able to compare and evaluate different theories when given suitable information.

explain and evaluate the effects of human activities on the atmosphere

describe why we do not know how life was first formed.

Earth’s atmosphere - Composition of air For 200 million years, the proportions of different gases in the atmosphere are similar to those today: ■ 78.1% nitrogen ■ 20.9% oxygen ■ other gases: carbon dioxide (0.04%), water vapour (0.25%) and argon (0.9%). The density of air at sea level is about 1.2 kg/m3 (1.2 g/L). Origin of atmosphere There are several theories about how the atmosphere was formed. 1. Earth
Earth’s crust - Earth’s structure: The Earth consists of a core, mantle and crust, and is surrounded by the atmosphere. Tectonic plates: The Earth’s crust and the upper part of the mantle (lithosphere) are cracked into a number of large pieces called tectonic plates. Wegener’s theory  of continental drift (crustal movement) Alfred Wegener (1880-1930) proposed the theory of continental drift at the beginning of the 20th century. His idea

Assessment and practical opportunities

investigating the composition of air by passing air over heated copper using gas syringes and measuring the percentage of oxygen. Then burning magnesium in the nitrogen to form Mg3N2. Add water to produce ammonia (nitrogen must have come from the air)

collecting gas produced by aquatic plants and testing for oxygen (using dissolved oxygen sensor)

measuring the amount of carbon dioxide in inhaled and exhaled air (using carbon dioxide sensor)

testing the products of combustion of fuels to show that carbon dioxide is produced

design an investigation to compare the amount of carbon dioxide released by reacting crushed shells (eg cockle, oyster) with dilute hydrochloric acid.