=Chemical Reactions= [image:] === ===(a very cool reaction between Mercury(II) thiocyanate and Ammonium chromate, two highly toxic compounds) ===In a chemical reaction one or more new substances are produced.=== [image:] Signs of a chemical reaction include: • Colour change • A Gas is produced • Change in temperature e.g. Heat is given off • A solid (precipitate) forms • A change in the smell [image:] During a chemical reaction chemical bonds between atoms are broken or formed. In this example hydrogen and oxygen are mixed together and they react to form water (a compound). Mixing two substances together is not a chemical reaction because no new substance has been formed. Only once chemical bonds have been broken or formed has a reaction occurred. In this example you can see that bonds within both the hydrogen and oxygen molecule have been broken and bonds between the oxygen and hydrogen atoms have been formed.
Credit: Ben Himme