Science: Reactions Flashcards
In a chemical reaction word equation, what are on the left and what are on the right of the equation arrow?
The reactants are on the left side of the arrow and the products are on the right side of the arrow
What is CONSERVATION OF MASS?
In a reaction the mass will be conserved, this means that the total mass of the reactants will be equal to the total mass of the products
If it appears that some of the mass has been lost, this means that a gas has been produced and escaped, accounting for the lost mass
What are BALANCED SYMBOL EQUATIONS?
Balanced symbol equations show the amounts of all of the individual atoms in a reaction
• The symbols used are from the Periodic Table
• They also show:
-Formulae of reactants and products
-How the atoms are rearranged
-Relative amounts of reactants and products
Eg. 2H2 + O2 ➞ 2H2O
What is COMBUSTION?
Combustion is the burning of a fuel in oxygen
What are examples do FUELS
Examples of fuels include petrol, diesel, coal and hydrogen
Why is hydrogen better than fossil fuels as a fuel?
it does not produce carbon dioxide:
What are EXOTHERMIC reactions?
+ what happens to surroundings when they happen?
Exothermic reactions involve a transfer of energy from the reactants to the surroundings
As energy is transferred to the surroundings this will show an increase in temperature
What are EXAMPLES of exothermic reactions?
Examples of exothermic reactions include combustion, freezing, and condensing
What are ENERGY LEVEL DIAGRAMS?
Energy level diagrams show the values of energy between the reactants and the products in a reaction
• If the energy is greater in the reactants than the products then the reaction is exothermic as energy has been given out to the surroundings
• If the energy is lower in the reactants than the products then the reaction is endothermic as energy has been taken in from the surroundings
What is a THERMAL DECOMPOSITION reaction? + an example
A thermal decomposition reaction is one where the reactants are broken down (decomposition) using heat (thermal energy)
• An example of this is with metal carbonates:
zinc carbonate ➞ zinc oxide + carbon dioxide
How do you test for carbon dioxide?
We can test for this carbon dioxide by bubbling the gas through limewater, if the limewater turns cloudy, the gas is carbon dioxide
How must chemical bonds be broken?
Energy must be used to break chemical bonds, meaning that this reaction is endothermic
