Chemical Reactions Flashcards
What is a physical change?
a change that does not make a new substance and is often reversible (just changes state, size or shape)
What is a chemical change
a change that creates a new substance and is often irreversible (Reactant atoms are rearranged to form a new product)
What are some examples of a physical change?
ice melting, shredding paper, breaking a glass bottle, crumpling up a piece of foil
What are some examples of a chemical change?
cooking a raw egg, baking bread, rust forming on an iron nail, burning wood
What are some ways to identify if a chemical change has occurred?
formation of a gas, colour change, temperature change, energy emitted , production of a new odour/smell
What is combustion?
commonly known as burning
What are the 3 things needed for a combustion reaction?
oxygen, fuel (hydrocarbon) and heat (triangle)
Combustion equation:
fuel + oxygen –> carbon dioxide + water
Name some examples of fuels:
wood, oil , natural gas, coal , hydrogen
What is very fast combustion?
An explosion
What is respiration?
a chemical reaction in the body cells to release energy
What is aerobic respiration?
respiration with oxygen ; glucose + oxygen
–> carbon dioxide + water
Where does aerobic respiration take place?
mitochondria
What is ATP?
an energy molecule that is made during aerobic respiration releasing chemical energy from sugar
What is anaerobic respiration?
respiration without oxygen (used when doing intensive exercises) ; glucose (in water) –> ethanol + carbon dioxide (+ energy) e.g. fermentation to make alcohol and bread
Describe conservation of mass:
when mass is never lost or gained in a chemical reaction or a physical change as long as the products are not allowed to escape; atoms are just rearranged as no atoms are destroyed or created
What is rusting?
rusting (chemical change) is the corrosion of iron. other metals corrode in a similar way but rusting is specific to iron ( it is orange and is an example of an oxidisation reaction)
What are 2 things needed for rusting?
Oxygen and water
The word equation for rusting?
Iron+ oxygen + water –> (hydrated) iron oxide
List some preventions of rust:
-painting over metal
-adding oil or grease
-galvanising (zinc protecting iron)
Another name for water:
dihydrogen monoxide
What are the 3 rules for balancing equations?
-you cannot change the subscript numbers
-balance equations must be in pencil
-coefficients have to be whole numbers
Steps for balancing an equation:
1) count atoms of each element on both sides
2) look where they do not match
3) find lowest common multiple
4) add coefficients in front of the chemicals (have to be whole numbers)
