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Chemical changes - Coggle Diagram
Chemical changes
Chemical change occurances
Mixing
Combine irreversibly into 1 or more products
Heating
Increase in temperature to heat up substances
Exposure to light
Photosynthesis in chlorophyll
Interaction with oxygen
Rusting, cellular respiration
Prevented by coating with paint or other materials
Using an electric current
Cause particles of electrical conductors to flow in direction of charge
Can coat objects with different metals
Types of chemical changes
Thermal decomposition
Substance breaks down upon heating
Breaks down into 2 or more simpler substances
Combustion
Requires presence of oxygen and heat
Heat and light are usually given out
Form one or more new substances
Oxidation
When a substance gains oxygen
ie, Rusting
Acid reactions
Neutralisation
Acid + alkaline
Results in a salt + H2O
pH level neutralises
Can be used in soap or to neutralise stomach acids
Acid with a metal
Acid + metal
Results in salt + Hydrogen
Lighted splint extinguishes with a "pop" sound
Effervescence is observed
Acid with a carbonate
Acid + carbonate
Results in salt + CO2 + H2O
Limewater turns cloudy with a white precipitate
Effervescence is observed
Signs of change
Chemical change
Combine or break down
New substance is formed
Usually irreversible
Products' properties are different from reactants
Physical change
No new substance is formed
Process is usually reversible
pH levels and indicators
pH scale
from pH 0 to pH 14
<7 is acidic, >7 is alkaline
pH 7 is neutral (ie. pure water)
Indicators
Litmus paper
Red in acid
Blue in alkali
Remains the colour it was in neutral pH
Universal indicator
Red is acidic
Green is neutral
Blue-purple is alkaline
Rearrangement of atoms
Atoms in reactants is equal to atoms in products