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chapter 18: chemical changes - Coggle Diagram
chapter 18: chemical changes
kinds of changes
physical changes
a physical change is a change in which no new substance is formed
chemical changes
a chemical change is a change in which a new substance is formed
it is also known as chemical reaction
how do we represent chemical reactions?
word equations
reactants (left hand side)
products (right hand side)
conditions (on top of arrow in the chemical reaction)
what happens when matter and heat interact
combustion
a substance reacts when oxygen when heated to form one or more new substances
heat and sometimes light are given out
lots of heat energy is usually released very quickly
oxidation
addition of oxygen to a substance in oxidation
oxidation reactions also occurs when other elements metals and non-metals burn in air
examples: rusting
ONLY IRON AND STEEL WILL RUST!!
thermal decomposition
a single substance breaks up into two or more simpler substances when heated
respiration
reactants: glucose and oxygen
products: carbon dioxide, water and energy
what happens when matter and light interact
photosynthesis
reactants: carbon dioxide + water
light energy from the sun trapped by chlorophyll
products: glucose + oxygen
photography
reactants: silver bromide
process: light
products: silver (grey solid) + bromine
what happens when matter and electricity interact
electrolysis
products: copper + chlorine
process: electricity
reactants: copper chloride (decomposition)
3 types of chemical reactions
chemical reaction 3
acid + alkali -> salt + water
chemical reaction 2
acid + carbonate -> salt + carbon dioxide + water
chemical reaction 1
acid + (reactive) metal -> salt + hydrogen
copper, silver and gold metals are unreative with acid
benefits and harmful effects of chemical changes
benefits
combustion of fuel allows food to be cooked
medicines help to relieve pain and discomfort in our bodies
alkali is cleaning agents that can remove dirt and grease
matter decay releases nutrients to soil, carbon dioxide given out for photosynthesis
harmful effects
harmful gases like nitrogen dioxide, sulfur dioxide and carbon monoxide that dissolves in rainwater produces acid rain, killing plants fishes and destroying building.
carbon monoxide and black soot particles causes lung cancer