Science - Teachers Sri Lanka

Step 3.10.2 : • Devide the class into four groups
• Provide the groups with instrutions for exploration, demy
paper and pastel
• Assign the tasks and engage groups in exploration.
• Prepare the groups for whole class presentation.
(60 mts.)
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Step 3.10.3 : • Get the groups to present their findings to the class.
• Give the first oppotunity for elaboration to the respective group
which made the presentation.
• Get the other groups propose construtive suggestions.
• Summerize highlighting the following points.
• If heat is given out during a chemical reaction the temperature
of the reacting mixture increase.
• Reaction which liberate heat during reactions are exothermic
reactions.
• If heat is absorbed during a chemical reaction the tempera
ture of the reacting mixture decrease.
• Reactions which absorb heat during areaction are endothermic
reactions.
• In an exothermic reaction, the energy in the product is less
than that of the reactants.
• In an endothermic reaction the energy in the products is
more than more than that of the reactants.
• It is important to use quatities of reactanta which show
practically measurable temperature difference.
• In this experiment we hypothesize that,
• The entire quantity of heat associated with the reaction
was used to change the temperature of the reacting
mixure.
• Heat capacity of solutions is equal to the heat capacity
of water.
• The density of the solution is equal to the density of
water.
• Change of heat calculated in a reaction, change with the
physical nature of the product and reactants.
• Therefore when change of heat associated with a reaction is
stated it is necessary to indicate the physical state of reactants
and products.
• To observe a maximum change in temperature the loss of
heat to the enviroment must be minimized.