AQA AS Physical Chemistry Exam Questions and Answers

AQA AS Physical Chemistry Exam Questions and Answers Who described atoms as solid spheres that make up different elements and when? - Answer- John Dalton in the 19th century Who suggested that atoms of a particular element had the same mass and atoms of different elements had different masses and when? - Answer- John Dalton in 1803 Who discovered the electron and when? - Answer- JJ Thomson, 1897 discovered electrons proving atoms weren't indivisible or solid. New model named plum pudding model Describe the plum pudding model - Answer- A ball of positive charge with negative electrons in embedded in it Who disproved the plum pudding model and how? - Answer- Rutherford and Geiger + Marsden By conducting the gold foil experiment. Positively charged alpha particles were fired at a very thin sheet of gold foil. If the plum pudding model was correct then the charged particles would have mostly deflected off the gold foil, but most of the particles passed straight through. Who discovered radioactivity and when? What did this show? - Answer- Henri Bequerel in 1896. Particles could come from inside the atom. State the three subatomic particles and name were they are found. - Answer- Protons - in the nucleus Neutrons - in the nucleus Electrons - in orbitals around the nucleus What is the (relative) charge and the (relative) mass of protons? - Answer- Charge: +1.062 x 10^-19 Relative charge: +1 Mass: 1.673 x 10^-27 kg Relative mass: 1 What is the (relative) charge and the (relative) mass of neutrons? - Answer- Charge: 0 Relative charge: 0 Mass: 1.675 x 10^-27 kg Relative mass: 1 What is the (relative) charge and the (relative) mass of electrons? - Answer- Charge: - 1.062 x 10^-19 Relative charge: -1 Mass: 0.911 x 10^-30 kg Relative mass: 1/1840 What is an orbital? - Answer- A region of space where there is a 95% chance of finding an electron How are the protons and neutrons held together? - Answer- By strong nuclear forces. Why does the repulsion between protons not make the nucleus fall apart? - Answer- Nuclear forces are much stronger than the electrostatic forces that hold the electrons and protons together. This means that they can overcome the repulsion between the protons in the nucleus. Why do elements in the same group have similar chemical properties? - Answer- They have the same number of electrons in their outer shell Define the term 'isotope' - Answer- Atoms of the same element which have the same number of protons but different numbers of neutrons Why do different isotopes of the same element react chemically in exactly the same way? - Answer- They have the same electronic configuration What is carbon dating? - Answer- The process of using the radioactive isotopes in carbon-14. All living things contain carbon-14. Carbon-14 decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food. Once the organism dies, however, it cannot absorb carbon-14. This means that the amount of the radiocarbon in its tissues steadily decreases. Because carbon-14 decays at a constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its resid