Energy changes Flashcards
What is a Exothermic reaction?
Transfers energy from the reacting molecules to surroundings.
Does the temperature go up or down in a Exothermic reaction?
Temperature goes up.
Give 3 examples of Exothermic reactions.
Combustion
Oxidation
Neutralization
Name 2 uses of exothermic reactions.
Self heating cans
Hand warming gloves
What is a Endothermic reaction?
Energy is taken into from their surroundings, this causes of the temperature around surroundings to get colder.
Name 2 examples of Endothermic reactions.
Thermal decomposition
Citric acid and sodium hydro-carbonate ( sherbert)
Name a use of Endothermic reactions.
Sports ice pack.
Energy is also what?
Conserved, in all chemical reactions, the amount of energy in the universe at the end of a chemical reaction is the same before the reaction takes place.
Describe the required pratical to measure temperature change of a chemical reaction of the neutralisation reaction between hydrochloric acid and Sodium hydroxide?
1) Put 25 cm3 of 0.25mol/dm 3 of hydrochloric acid and sodium hydroxide in separate beakers.
2) Place in a waterbath set to 25’C untill they are both at the same temperature.
3) Add the HCI followed by Sodium hydroxide to a polystryene cupp with a lid.
3) Take temeprature of the mixture every 30s and record highest temperature.
4) Repeat steps 1-4 using 0.5 mol/ dm 3 and then 1 mol / dm 3 of Hydrochloric acid.
What is the Independent variable of this experiment?
Volume of hydrochloric acid solution
What is the Dependent variable?
Maximum temperature reached.
What is the Control variable?
Volume of hydrochloric acid.
Why might you use a Polystyrene cup for this expermient?
we are measuring temperature so we want to reduce any heat lose, Polystyrene is a good thermal insulator, reducing heat lose from side and bottoms.
Why might you use a Lid to cover solution in experiment?
Reduce heat from air.
In a rate
The reactants start with the highest amount of energy, as reaction prog
