Science B Notes

Topics: Oxygen, Carbon dioxide, Carbon Pages: 17 (3731 words) Published: April 28, 2013
cientists have used different types of evidence to prove the many changes that have taken place in the universe and on our own planet over time. Living organisms have also adapted to the changing environmental conditions. In this theme there are four contexts:

1 Our changing universe

2 Our changing planet

3 Materials our planet provides

4 Using materials from our planet to make products

Additional guidance 2. Knowledge of telescopes should be limited to their use: no working details are required.

4. Treatment of red-shift should be limited to a study of the black lines within the spectrum.

Our changing universe Candidates need to understand that: For many centuries, our ancestors thought the Earth was the centre of the universe. Science has since taught us that this is incorrect. We know that the Earth lies within the Milky Way galaxy (a group of stars), which is located somewhere within the universe. Scientists have discovered that the Sun is one star in the Milky Way. Even smaller in scale than a galaxy is a solar system. Our solar system comprises one star (the Sun) and planets orbiting it. Scientists use many different techniques to observe and search for patterns in the universe in an attempt to understand and gather evidence concerning how it began, what it is like and how it is changing. They have gathered much evidence from the use of telescopes, both on Earth and in space, and from the study of light reaching us from stars in distant galaxies.

Candidates need to:

1. Know that observations of the solar system and the galaxies in the universe can be carried out on the Earth or from space.

2. Know that observations are made with telescopes that may detect visible light or other electromagnetic radiations such as radio waves or X-rays from space, and that these observations provide evidence for changes taking place in the universe.

3. Understand that if a wave source is moving relative to an observer there will be a change in the observed wavelength and frequency (Doppler effect).

4. Explain why there is a red-shift in light observed from most distant stars and galaxies. The further away stars or galaxies are, the more their light is red-shifted. This indicates that distant galaxies are moving away from us, and that the further away a galaxy is the faster it is moving away.

5. Explain how the observed red-shift provides evidence that the universe is expanding and supports the ‘Big Bang’ theory (that the universe began from a very small initial point).

Within this context, candidates should be able to use scientific data and evidence to discuss, evaluate or suggest implications of the following:

the position of the Earth in the solar system

the evidence for the origin, structure and continuing evolution of the universe.

2 Our changing planet

Candidates need to understand that: The Earth is a planet that has changed since its formation and is still changing. The surface of the Earth has cooled after a period of intense volcanic activity and has become able to sustain plant and animal life. The surface of the Earth continues to change due to the activity of volcanoes and earthquakes, mainly along the edges of tectonic plate boundaries. Alongside these changes the atmosphere has altered to enable life to evolve, from being rich in carbon dioxide to containing enough oxygen to support life. Environmental scientists are beginning to understand the processes that cause the natural greenhouse effect and maintain the heat balance and global climate that enable life on Earth.

Candidates need to:

1. Know that the surface of the Earth has changed over time as a result of cooling.

2. Know that the Earth consists of a mantle, core and crust, surrounded by the atmosphere.

3. Know that the Earth’s crust and the upper part of the mantle are cracked into a number of large pieces (tectonic plates).

4. Explain how convection currents within the mantle cause the...
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