21) What is the modern definition of an alkane?
22) What element has the symbol Si?
23) What type of reaction is a double displacement reaction?
24) What is a Lewis acid?
25) What type of reaction is photosynthesis?
26) What process is used to convert the energy stored in coal into useful energy such as electricity?
27) In what type of reaction does an atom gain or lose electrons?
28) What is the symbol for iron?
29) What type of energy is released when an atom undergoes fission?
30) What is the symbol for chlorine?