What is the conservation law explained?
Energy is always conserved in reactions, if a chemical reaction transfers energy to the surroundings, the molecules of the product produced must have less energy than the reactants
What is an exothermic reaction?
Reaction that transfers energy to the surroundings and saw the temperature of the surroundings increase
What are some examples and every day use of exothermic reactions
Combustion oxidation reactions, neutralisation
Everyday uses-handwarmers self heating cans
What is an endothermic reaction?
Reaction which takes energy in from the surroundings, and so the temperature of the surroundings decrease
What is an examples and every day uses of endothermic reactions
Thermal decomposition , reaction between sodium, hydrogen carbonate and citric acid
Everyday used-sports injury pack
what is activation energy
The minimum amount of energy particles must have to react
Describe energy in terms of breaking and making bonds
. Energy is taken into break bonds in the reactants.
. Energy is released to form bonds in the products.
What is the equation for energy, change and bonds?
Overall energy of reaction= sum of energy needed to break bonds in the reactants - sum of the energy released when forming bonds in the products
Describe exothermic reactions in terms of energy and bonding
The energy released when forming new bonds is greater than the energy needed to break existing bonds
Describe endothermic reactions in terms of energy and bonds
The energy needed to break existing bonds is greater than the energy released when forming new bonds
What are reaction profiles
They are used to show the relative energies of reactants and products
Overall energy change an activation energy
Describe the exothermic reaction, energy profile
X axis-progress of reaction.
Y axis- energy
Reactants are higher than the products
From reactants to peak-activation energy
From reactants to products-energy released
Describe the endothermic reaction, reaction profile
X axis-progress of reaction
Y axis-energy
Products are higher than reactants
Reactants to peak-activation energy
Reactants to products-energy, absorbed
State the equation and bonding of complete combustion
CH4 + 2O2 ——> CO2 + 2H2O
H | H-C-H. + O_-O O_-O + O-_C-_O + H-O-H |. H-O-H H
What happens when bonds are broken?
Heat taken in temperature change of the surroundings decrease is endothermic
What happens when bonds are formed
Heat is given out temperature change of surroundings, increases exothermic
What is a cell?
A cell contains chemicals which react to produce electricity
How can you make a simple cell?
By connecting to different metals in contact with an electrolyte
In a cell, what does the voltage produce depend on?
Type of electrode
Electrolyte
Describe a simple cell diagram
Two Electrodes inside an electrolyte, connected by wires with a volt meter in the middle.
What is the battery?
Battery consists of two or more cells connected in series. Used for a greater voltage.
What is a non-rechargeable battery and give an example
When one of the reactants is used of the chemical reaction stops
Alkaline battery
What is a rechargeable battery and give an example
The chemical reactions are reversible when an external electric current s applied
Mobile phone batteries
Describe a fuel cell
A cell which is supplied with an external source of fuel. The fuel is oxidised electrochemically within the fuel cell to produce a potential difference.
Oxygen and hydrogen
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Reactions 226
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C1-Periodic Table+Atomic Structure59
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C2-bonding,structure And Properties Of Matter46
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C3-quanititive Chemistry51
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c4 - Chemical Changes52
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C5-Energy changes30
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C2-bonding Mocks54
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C6-The Rate And Extent Of Chemical Change41
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C7-Organic Chemistry41
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C1-Periodic Table + Atomic Structure (GCSE)73
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C8-Chemical Analysis GCSE34
