PMT

• What is an atom?

  An atom is the smallest part of an element.
• What is an element?

  An element is a substance of one type of atom.
• How are elements listed and approximately how many are there?

  They are listed in the periodic table; approximately 100.
• Into what two groups can elements be classified based on their properties?

  Metals and non-metals.
• What are the new substances formed when elements combine through chemical reactions called?

  Compounds.
• What is a compound?

  Two or more elements combined chemically in fixed proportions.
• Do compounds have the same properties as their constituent elements?

  No, they have different properties.
• What is a mixture?

  A mixture consists of two or more elements or compounds not chemically combined.
• Does a mixture have the same chemical properties as its constituent materials?

  Yes, it does have the same chemical properties.
• What are the methods through which mixtures can be separated?

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
  • They do not involve chemical reactions
• Describe simple distillation.

  It separates liquid from a solution by boiling and condensing.
• What happens during evaporation in crystallisation?

  Solvent evaporates, leaving solid behind.
• How does crystallisation differ from evaporation?

  Crystallisation removes some solvent to form crystals.
• Describe fractional distillation.

  It separates liquids with different boiling points using a fractionating column.
• What is the purpose of the fractionating column in fractional distillation?

  It helps to separate compounds based on boiling points.
• Describe filtration.

  It separates insoluble solids from liquids using filter paper.
• What is chromatography used for?

  It separates a mixture of substances dissolved in a solvent.
• What is a separating funnel?

  A separatory funnel is for separating immiscible liquids.
• Describe the plum-pudding model of the atom.

  The atom is a ball of positive charge with negative electrons embedded.
• What does the nuclear model of the atom suggest?

  Electrons orbit the nucleus at specific distances (shells).
• What are the smaller positive particles discovered in the nucleus called?

  Protons.
• What did James Chadwick's work provide evidence for?

  The existence of neutrons in the nucleus.
• Describe the structure of an atom.

  An atom has a small central nucleus with protons and neutrons, surrounded by electrons.
• What are the relative masses of protons, neutrons, and electrons?

  Masses: 1, 1, very small.
• Why are atoms electrically neutral?

  They have the same number of electrons and protons.
• What is the radius of an atom?

  0.1 nm.
• What is the radius of a nucleus compared to that of an atom?

  1 x $10^{-14} \text{ m}$ and 1/10000.
• What name is given to the number of protons in the nucleus?

  Atomic number.
• Why are atoms electrically neutral?

  They have the same number of electrons and protons
• What is the radius of an atom?

  0.1 nm
• What is the radius of a nucleus?

  $1 \times 10^{-14} \text{ m}$
• How does the radius of a nucleus compare to that of an atom?

  It is 1/10000 of the atom's radius
• What is the name given to the number of protons in the nucleus?

  Atomic number
• Atoms of the same element have the same number of which particle in the nucleus?

  Protons
• Where is the majority of mass of an atom located?

  The nucleus
• What is the mass number?

  The total number of protons and neutrons
• How do you calculate the number of neutrons using mass number and atomic number?

  Subtract the atomic number from the mass number
• What is an isotope?

  Atoms of the same element with different neutrons
• Do isotopes of a certain element have the same chemical properties?

  Yes, they have the same electronic structure
• What is the relative atomic mass?

  The average mass value of isotopes