Chemistry
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Which changes of state need energy?
Melting, evaporating and sublimation
What is an atom?
Simplest thing that can exist on its own
What is a molecule?
2 or more atoms joined together by covalent bonds
What is an ion?
Charged particle
What is a mixture?
2 or more substances not chemically joined together
Describe the structure of the atom
Nucleus that contains protons and neutrons with electrons in shells orbiting it
What is the mass of a proton? neutron? electron?
P= 1, n = 1, e 1/1840 or negigible
What are the charges on a proton? neutron? electron?
p = +, n = 0, e = -
What does the proton number (atomic number) tell you?
Number of protons (which equals the number of electrons in an atom)
How do you work out the amount of neutrons?
Mass number - atomic number
How is a positive ion formed? What does this happen in?
Lose an electron - metals
How is a negative ion formed?
Gain an electron - non metals
What happens in an ionic bond?
Electrons are given from metals to non-metals
What happens in a covalent bond?
Electrons are shared between non-metals
Which is the stronger bond covalent or ionic?
Ionic
What are the differences between ionic and covalent compounds?
Ionic have higher mpt and bpt, are soluble in water, conduct electricity when molten, not volatile (do not evaporate easily)
What does exothermic mean?
Gives out heat or energy
What does endothermic mean?
Takes in heat
In a chemical reaction what happens?
Bonds broken (endothermic) then new bonds made (exothermic)
What is loss of oxygen in a reaction called?
Reduction
What is gain of oxygen in a reaction called?
Oxidation
In the reaction Ca0 + Mg = MgO + Ca What was oxidised and what was reduced?
Ca = reduced Mg = oxidised
What does the group number on the periodic table tell you?
Number of outer electrons
What are group 1 called?
Alkali metals