Science: Final Exam Ch6

what is a chemical reaction

a chemical reaction occurs when substances change into new substances or where atoms are rearranged to form new subtances

physical change: a change that doesnt create a new substance and is usually reversable

signs of a chemical reaction

color change, gas produced, temprature change, light produced, formation of a solid

genereal formula for reactions with water

metal + water → metal hydroxide + hydrogen gas

reactions with metal and water

potassium: instant, violent reaction; produces a lilac flame

sodium: instant reaction; water gets hot; moves on surface

magnesium: very slow reaction with cold water

copper/iron: no reaction with cold water

metal + water word equation

metal + water → metal hydroxide + hydrogen gas

metals + oxygen word equation

metal + oxygen → metal oxide

metal + dilute acids word equation

metal + dilute acid → metal chloride + hydrogen gas

combustion

combustion means the burning of fuel in oxygen

fuel + oxygen → heat + light

chemical vs physical change

physical chage:

no new substances formed, usually reverseable, examples melting ice

chemical change:

new substances formed, usually irreversable, examples rusting