Science

• Atom: the smallest particle of a chemical element that can exist.
• Compound: a thing that is composed of two or more separate elements; a mixture
• Chemical reaction 2: The reactants are combined to form a new substance.
• Who conducted the gold foil experiment and in what year?

  Ernest Rutherford in 1909
• What was the primary purpose of the gold foil experiment?


  To provide evidence for the nuclear model of the atom
• What happened to most of the alpha particles during the gold foil experiment?


  They passed straight through the gold foil
• What did the deflection of a small fraction of alpha particles indicate about the structure of the atom?


  It indicated that the atom is mostly empty space with a dense nucleus
• What was the prevailing model of the atom before the gold foil experiment?

  The plum pudding model
• According to the nuclear model, where are electrons located?


  In the surrounding space of the nucleus
• What are the key findings of the gold foil experiment?


  • Most alpha particles passed through the foil
  • A small fraction were deflected at large angles
  • Some particles bounced back
  • Indicated a dense, positively charged nucleus
  • Atoms are mostly empty space
• How did the results of the scattering experiment contribute to modern atomic theory?


  They provided strong evidence for the nuclear model of the atom
• What does the nuclear model of the atom propose?


  Atoms consist of a central nucleus surrounded by electrons
• What was the significance of the gold foil experiment in atomic theory?


  • Led to the acceptance of the nuclear model
  • Showed that atoms have a dense nucleus
  • Changed the understanding of atomic structure
  • Laid the foundation for modern atomic theory
• Structure of an atom: Protons, neutrons and electrons.
• atomic number - number of protons and therefore electrons
• Separating a mixture is when you separate the components of a mixture by physical means.
• To purify a mixture, the solvent is evaporated and the solute is separated from the solvent
• What is chromatography used for?


  To separate and analyze mixtures of substances
• How does chromatography distinguish between pure and impure samples?


  By separating components and analyzing their presence
• What are the main components involved in chromatography?


  • Stationary phase (e.g., paper or solid column)
  • Mobile phase (e.g., liquid or gas)
• What happens to a sample placed on the stationary phase in chromatography?


  It is passed through by a mobile phase
• Why do different components in a sample move at different rates during chromatography?


  Due to their varying affinities for the stationary phase and solubility in the mobile phase
• What does a pure sample produce on a chromatogram?


  A single spot or peak
• What does the presence of multiple spots or peaks in a chromatogram indicate?


  The sample is impure and contains more than one substance
• How can the purity of a sample be determined using chromatography?


  By comparing the number and position of the spots or peaks
• What is a retention factor in chromatography?


  It is used to identify substances based on the distance traveled by each component
• What is the summary of chromatography's function?


  • Separates components of a mixture
  • Allows visual analysis of their presence
  • Distinguishes between pure and impure samples
• Kinetic energy is the energy of a moving object, measured in joules (J)
• Gravitational potential energy - the energy an object possesses due to its position in a gravitational field
• Elastic potential energy - energy stored in a stretched spring or elastic object.
• Thermal energy is the energy of motion of particles in a substance due to their random motion
• Nuclear energy is the energy released by the splitting of the nucleus of an atom.
• Electrostatic energy is the energy stored in the electrostatic forces between two charged objects.
• Magnetic energy is the energy stored in magnetic fields.
• Chemical energy- the energy stored in the bonds of chemical compounds which can be released during a chemical reaction.
• Mechanical pathway- using force
• By heating
• By radiation
• Electrical - through the flow of electric Charge
• Work done = force x distance