Exethermic endothermic and chemical changes Flashcards
What is an EXOTHERMIC reaction?
Exothermic reactions release energy in to the surroundings (Temperature Rises)
What is an ENDOTHERMIC reaction?
Endothermic reactions take in energy from the surroundings.
Put these in order of reactivity:
GOLD LEAD POTASSIUM SODIUM ZINC IRON MAGNESIUM COPPER
Most Reactive:
Potassium Sodium Magnesium Zinc Iron Lead Copper Gold
Least Reactive:
What is a Metal Displacement reaction?
A metal Displacement reaction happens when a more reactive metal is added to the compound of a less reactive metal.
Where is Hydrochloric acid found?
In the Stomach
What does zinc react with to produce a flammable gas
It reacts with acid
What is Dela?
A change in something (Δ)
What is Delta H?
A change in energy (ΔH)
The Delta H is negative for what
Endothermic or Exothermic reactions?
Exothermic reactions
The Delta H is positive for what
Endothermic or Exothermic reactions?
Endothermic reactions
What is the unit for Delta H?
KJ/Mol (Kilojoules per mole
when doing an experiment whereby you use two metals and put them on a positive and a negative terminal, What happens to the voltage when two pieces of the same metal are used?
The voltage is zero
What increases the size of the voltage?
The further apart the two metal are in the reactivity series.
What voltage is recorded when the more reactive metal is attached the positive terminal of the
voltmeter?
A positive voltage is recorded and vice versa with a reactive metal in the negative terminal
In a normal cell, what happens to the chemicals
They gradually get used up, as one of the chemicals gains electrons (reduction) and the other chemical loses electrons (oxidation)
What happens to the more reactive metal when it loses electrons
The more reactive metal loses electrons (is oxidised), donating them to the ions of the less reactive metal.
What is the problem with fossil fuels?
They are non-renewable and cause pollution.
What is one alternative fuel to fossil
Hydrogen is one alternative fuel. it can be burned in combustion engines or used in fuel cells to power vehicles
Describe what a fuel cell is:
A more efficient use of the energy from oxidising hydrogen is in a FUEL CELL. These cells are fed with hydrogen and oxygen and produce water. most of the energy released in the reaction is transferred into electrical energy. This can be used to power vehicles. However, a constant supply of hydrogen is still required to run the fuel cell.
What is the equation for the energy change
2H2 (g) + O2 (g) -> 2H2 O(I)
