Title: Exothermic and endothermic Reactions Complete the word equations for these acid metal reactions.

a) zinc + hydrochloric acid  ______+ ______

b) zinc +  ______+ ______

c) zinc + nitric acid  ______+ ______

Extension: Write the symbol equation for the above reactions. Enter the room in silence. Put your planner, pencil case, exercise book and any other equipment you will need on your desk. Place your bags in the cupboards. Describe Describe examples of exothermic reactions.

Prior knowledge: Explain the energy changes taking place during an exothermic reaction

exothermic reaction chemical bond bond making bond breaking Energy changes occur in all chemical reactions. In some reactions there is a very clear energy change, with the transfer of energy by , light and sometimes sound to the surroundings.

These are exothermic reactions – exothermic means ‘to give out heat’.

Exothermic reactions can be recognised because the temperature of the products is higher than the temperature of the reactants. The bigger the temperature rise, the more exothermic the reaction. https://www.youtube.com/watch?v=GyVD8V0016w

•Adding strong bases or reactive metals to strong acids, causes the temperature to increase dramatically.

•The reaction between iron wool and – a type of hand-warmer – makes use of the heat produced.

•Adding calcium oxide (quicklime) to a bath of cold water, produces such an exothermic reaction that the cold water boils after about ten minutes!

•In the reaction, aluminium powder reacts with iron oxide using a magnesium fuse – aluminium is more reactive than iron, displacing it to produce iron metal. The reaction is highly exothermic, and the heat produced melts the iron. exothermic reactions release energy to the surroundings so the surroundings get hotter.  ex = out (as in ‘exit’)  thermic = relating to heat endothermic reactions absorb energy from the surroundings – so the surroundings get colder.  en = in (as in ‘entrance’) Carry out the different reactions. If the temperature goes up, it is an exothermic reaction. Increase in temperature

Draw a column and divide the pictures into either exothermic or endothermic reactions.

Exothermic Endothermic Exothermic or endothermic?

BBQ-BURNING CHARCOAL

EXOTHERMIC Exothermic or endothermic?

BOILING AN EGG

Hint: Is the egg absorbing energy or releasing energy to cook?

Boiling an egg is an because the egg won't cook unless we add energy. Exothermic or endothermic?

ICE BATH

ENDOTHERMIC- the ice melts because it takes in energy from the surroundings. Exothermic or endothermic?

HAND WARMER

EXOTHERMIC Exothermic or endothermic?

PHOTOSYNTHESIS During photosynthesis, plants absorb the energy from the sun to convert carbon dioxide and water into glucose and oxygen.

sunlight + 6CO2(g) + 6H2O(l)  C6H12O6(aq) + 6O2(g)

ENDOTHERMIC Exothermic or endothermic?

Combustion reaction

EXOTHERMIC reaction

In general, for complete combustion: hydrocarbon + oxygen → carbon dioxide + water Exothermic or endothermic?

Ice pack

ENDOTHERMIC Write a method to show how to prove that the reaction between acid and magnesium is exothermic.

Key words Boiling tube Pipette Thermometer Temperature During all chemical changes, the reactant particles undergo collisions.

During a collision, energy is absorbed from the surroundings to break chemical bonds within the reactant particles.

Once all the bonds have broken down, the reactant atoms are now free to form bonds with other reactant atoms and make new products.

During the formation of new bonds energy is transferred to the surroundings, usually in the form of heat. If the energy transferred to the surroundings during the bond- making process is higher than the energy absorbed during the bond- breaking process, the reaction is exothermic. Drinks have been developed that are self heating.

1) Name the reaction that is taking place. 2) State the units for temperature 3) State the units for energy 4) What are broken and formed again during chemical reactions?