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Elements of Life

Elements of Life. EL1: Where do elements come from?. Learning Objectives. Discuss how the elements were formed Explain how atomic theory has changed over time Evaluate different models of the atom (HSW). We are all made of star dust…. In the beginning there was….

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Elements of Life

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  1. Elements of Life EL1: Where do elements come from?

  2. Learning Objectives • Discuss how the elements were formed • Explain how atomic theory has changed over time • Evaluate different models of the atom (HSW)

  3. We are all made of star dust….

  4. In the beginning there was… • A lot of energy concentrated in a minute point (singularity) • For some reason it exploded creating space and time, and a very big bang! (approx 15 bya) • As ‘it’ cooled down the energy began to form matter. • Within the first few seconds protons, neutrons and electrons were created.

  5. Building blocks for the Universe • A few minutes after the big bang the first elements began to form (H, He, and a little Li) • Only NUCLEI (too much energy for electrons to remain bound, atoms are ionised, plasma) • It took a further 10 000 years for the universe to cool enough for the electrons to be captured! • Even now the universe is predominantly made up of hydrogen.

  6. Gravity • As matter formed gases and dust began to clump together (pulled together by gravity) making GAS CLOUDS • As gravity contracts the cloud it becomes very hot in the centre – plasma forms and it is hot enough for NUCLEAR REACTIONSto take place

  7. Nuclear v Chemical • Nuclear reactions (physics!) involves changes in an atom’s NUCLEUS • Chemical reactions involve a rearrangement of an atoms OUTER (valence) ELECTRONS

  8. A star is born • Nuclear FUSION create different elements • Nuclei combine and form new heavier elements. • V. high temp is needed to overcome the huge amount of electrostatic repulsion between +’ve charge nuclei • When H nuclei fuse ENORMOUS amounts of energy is given out. The dense gas cloud GLOWS it is now a STAR.

  9. Fusion reactions • We must also balance nuclear reactions: atomic mass and atomic number must be conserved. 1 H 1 2 H 1  3 He 2 + gamma + 2 H 1 + 3 H 1  4 He 2 + 1 n 0

  10. A load of hot wind! • Different nuclear reactions produce different (heavier) elements • Nuclear reactions generate a HOT WIND, which blows away some dust and gas. • These eventually form planets surrounding the star. …… To be continued……

  11. Activity EL1.1:What do we know about atoms? In groups of 3 you must research the work of • J.J. Thompson • Rutherford, Geiger and Marsden • Henry Moseley • James Chadwick • Find out • Who they were • Where they worked • What they knew about the atom • What they did (experiments!) • What conclusions they made • How the model of the atom changed as a result

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