chemistry

• What is a compound?

  A compound is a substance that contains two or more different types of atoms chemically bonded together
• What is the chemical formula for water?

  H2O
• How many hydrogen atoms are in one molecule of water?

  There are two hydrogen atoms in one molecule of water
• What does it mean if there is no number after a symbol in a chemical formula?

  It indicates there is an invisible one
• What do chemical reactions involve regarding atoms?

  Atoms change what they're bonded to and how they're bonded through chemical reactions
• How can we represent a chemical reaction?

  With a word equation and a chemical equation using symbols
• Why must chemical equations be balanced?

  Because atoms are not created or destroyed in a chemical reaction
• What is the first step in balancing a chemical equation?

  Start balancing atoms that are only in compounds
• What is a mixture?

  A mixture is any combination of different types of elements and compounds that aren't chemically bonded together
• Give an example of a mixture.

  Air, which is a mixture of oxygen and nitrogen
• How can large insoluble particles be separated from a liquid?

  Using filtration
• What is crystallization used for?

  To separate a solute from a solvent after evaporating the solvent
• What is distillation?

  Heating a solution to separate components based on boiling points
• What is fractional distillation?

  Separating different liquids in a mixture based on their different boiling points
• What are the three main states of matter?

  Solid, liquid, and gas
• How do particles behave in a solid state?

  Particles vibrate around fixed positions
• What happens to water when it is in a gaseous state?

  It is called water vapor, and the particles are far apart and move randomly
• What must be supplied to melt or evaporate a substance?

  Energy, usually in the form of heat
• What do we indicate with state symbols in chemical equations?

  The state of substances: solid (s), liquid (l), gas (g), and aqueous (aq)
• Who discovered that atoms are made up of positive and negative charges?

  JJ Thompson
• What is the plum pudding model of the atom?

  A model where a positive charge has electrons dotted around it
• Who discovered the nucleus of the atom?

  Ernest Rutherford
• What did Rutherford's experiment with alpha particles demonstrate?

  That atoms must be mostly empty space
• Who discovered neutrons?

  James Chadwick
• What is the charge of protons and electrons?

  Protons have a charge of +1 and electrons have a charge of -1
• What is the relative mass of neutrons?

  Neutrons have a relative mass of 1
• What does the atomic number represent?

  The number of protons in the nucleus
• What happens to an atom when it gains or loses electrons?

  It becomes an ion
• What is the mass number?

  The total number of protons and neutrons in the nucleus
• What are isotopes?

  Atoms of the same element with different numbers of neutrons
• Why might the mass number not be a whole number on the periodic table?

  Because it shows the average mass of all isotopes of that element
• What is relative abundance?

  The percentage of different isotopes of an element
• How do you calculate the average relative atomic mass of an element?

  Add up the total masses of all isotopes and divide by the total number of atoms
• How was the periodic table originally organized?

  Elements were ordered by their atomic weights
• Who grouped elements based on their properties rather than atomic weight?

  Dmitri Mendeleev
• What is the maximum number of electrons in the first four shells?

  2 in the first shell, 8 in the second and third shells, and 2 in the fourth shell
• What are metals and nonmetals in relation to the periodic table?

  Metals are to the left of the staircase and nonmetals are to the right
• What do group numbers in the periodic table indicate?

  The number of electrons in an atom's outer shell
• What are alkali metals?

  Group one metals that have one electron in their outer shell
• How does reactivity change in alkali metals as you go down the group?

  Reactivity increases as you go down the group