chemistry

• endothermic reactions take in energy from surroundings
• exothermic reactions transfer energy to its surroundings
• exothermic: as energy is given out to surroundings, energy of reactants is higher and products lower
• endothermic: product energy greater than reactant
• acid reactions release hydrogen ions
• acid + base - salt + water
• acid + metal - salt + hydrogen
• acid + carbonate - acid + carbon dioxide + water
• combustion reactions- fuel + oxygen - carbon dioxide
• complete combustion produces carbon dioxide and water
• incomplete combustion produces carbon monoxide and water or carbon and water
• Combustion

  The burning of fuel and oxygen to release energy
• Surface area speeds the rate of reaction as particles are around the reactant more
• pressure lowers space available meaning more collisions
• temperature particles gain heat energy and move faster and collide
• more concentration means more particles of reactant which makes collisions more likely
• Catalysts are chemicals added to speed up the reaction
• mass can neither be created nor destroyed in ordinary chemical and physical changes
• precipitation: the action or process of precipitating a substance from a solution, double displacement reaction
• decomposition: when one compound is broken down to produce two or more compounds
• double displacement involves two compounds, single involves element and compound
• corrosion is the formation of compounds on the surface of a metal. this occurs at different rates based on the reactivity of the metal
• metal+oxygen=metal oxide (corrosion)
• decomposition reaction occurs when one reactant breaks down into two or more products. it can be catalyses by energy input in form of heat electricity or light
• AB= A + B (decomposition)
• isotope is a variation of the same element with a different number of neutrons in the nucleus
• isotopes can be stable or unstable (radioisotope), stable have nuclei and are non radioactive, unstable have unstable nuclei, radioactive
• soluble salts can dissolve in water, insoluble require the presence of specific ions to dissolve
• ex. isotope - Carbon-12 and carbon-14
• polymers are large molecules made of monomers, biopolymers occur naturally
• natural radioactivity arises from the decay of nuclei in atoms, releasing particles and energy
• alpha decay- releases helium nucleus, mass number decreases by 4, atomic number decreases by 2
• beta decay- loss of an electron, mass stays the same but atomic number increases by 1 , write electron symbol
• gamma decay, excited state to lose energy (photons), no change in mass or number
• half life is the time that takes a radioactive isotope to decay 50% of its atomic mass
• nuclear fission is when a larger atom splits into two or more smaller ones, low energy
• nuclear fusion is when two or more lighter atoms form into a larger one, high energy
• chemical reactions involve energy transfer
• respiration: oxygen + glucose - carbon dioxide + energy (ATP)
• chemical reactions occur in living systems and involve energy transfer, ex, respiration and reactions involving acids in digestion