SACE STAGE 1 CHEM FIRST CHP

• Elements are organized in the periodic table according to their atomic number, electron configurations and chemical properties.
• In a chemical reaction, atoms on the left-hand side and right-hand side must be equal, meaning no new atoms are created or destroyed
• Atomic mass is based on carbon-12 as the standard, with one atomic mass unit defined as 1/12th the mass of one carbon-12 atom
• Molecular mass is the sum of atomic masses of the elements present in a molecule
• One mole of a substance contains as many particles as there are atoms in exactly 12g of carbon-12 isotope
• Molar mass is the mass of one mole of a substance in grams
• Balancing a chemical equation involves ensuring the same number of atoms of each element on both sides of the equation
• What is a mixture?

  A combination of two or more substances that are not chemically bonded.
• What is solubility?

  Solubility is the measure of the extent to which a solute dissolves in a solvent to form a homogeneous solution at a given temperature. Unit: g/L
• What are the three heat transfer processes?

  Conduction, convection, thermal radiation
• What is thermal conduction?

  Transfer of heat when particles collide and transfer thermal energy.
• What is thermal conductivity?

  The rate at which a material transfers heat through conduction.
• What is electrical conductivity?

  The ability of a material to conduct electric current or the rate at which charges flow.
• How are x-rays produced?

  When high energy electrons collide with a target material inside the x-ray tube.
• What are blowing agents?

  Low-boiling point materials that expand and form a gas when heated. Used for creating lightweight polymers as the expanding gas produces a porous structure that lowers the density and thermal conductivity of the material.
• Example of blowing agent?

  Pentane for polyurethane insulation
• Nanomaterials: Materials that are 1-100 nanometers in size.

  
• What is a homogenous mixture?

  A mixture with uniform composition such as air, seawater, beverages, vinegars, detergents and alloys.
• What is a Heterogenous mixture?

  Mixture with uneven distribution of substances.
• What is filtration?

  Separation of solid particles from a liquid or gas by passing it through a porous material. (for heterogenous mixture)
• What is evaporation?

  Separating a homogenous mixture containing one or more solutes in a solvent. Solute is left behind, solvent is evaporated.
• What is distillation?

  Distillation is a process used to separate and purify liquids based on their different boiling points. Heat is transferred to the mixture and the component with the lower boiling point vaporises and enters a condenser where it is liquid again. Used to separate water from a solution of salt in water.
• What is fractional distillation?

  Fractional distillation is a process used to separate different components of a liquid mixture whose difference in boiling points is less than 25 C. Used for separating gases from air and for components of petroleum.
• What is an atom?

  An atom is the basic unit of matter that consists of a nucleus containing protons and neutrons, surrounded by electrons.
• What are elements?

  Substances that cannot be broken down into simpler substances by chemical means and are made of one kind of atom only.
• What are compounds?

  Substances formed by the chemical combination of two or more elements and are in uniform composition.
• How many electrons in K, L, M, N sub shell respectively?

  K: 2 electrons L: 8 electrons M: 18 electrons N: 32 electrons
• What are electron shells? Energy levels or orbitals where electrons are found in an atom.
• Maximum number of electrons formula is 2n^2
• What is the main electron configuration of Potassium, calcium, scandium and titanium atoms?

  K- 2881

  Ca- 2882

  Sc- 2892

  Ti- 2 8 10 2
• Bohr atomic theory?

  Electrons occupied stationary orbits around the nucleus and were associated with a discrete amount of potential energy
• What do bright lines on the emission spectrum represent?

  Wavelengths of visible light that are emitted when electrons transition from higher to lower energy levels.
• When a continuous spectrum of visible light is transmitted through a gaseous or vaporised sample of element or compound, discrete wavelengths of light are absorbed by atoms in the sample resulting in a series of dark lines in the continuous spectrum
• What are dark lines?

  Absorption lines in a spectrum. Electrons as they transition from lower to higher
• Robert Bunsen and Gustav Kirchhoff discovered two new elements between 1860 and 1861 using their newly developed spectroscope. The elements were identified by vaporising samples of spring water and comparing the emission lines to those present in the line emission spectra of the known chemical elements
• Line absorption spectra are used to determine the elemental composition of the atmospheres of stars and planets. This is achieved by comparing the absorption spectrum of a star or planet with the line emission spectra of the chemical elements.
• What is an isotope?

  Atoms of the same element with different numbers of neutrons. (same atomic number, different mass number)
• What is the aufbau principle?

  Electrons fill atomic orbitals in order of increasing energy.
• Electronic configuration of chromium and copper?

  Ch- 4s1 3d5

  Cu- 4s1 3d10
• What is relative atomic mass?

  The weighted average mass of an element's isotopes.