section 4: chemical reactions Flashcards
chemical reaction
two or more substances combine to FORM NEW SUBSTANCE
chemical change
only occurred when a new substance has been made
evidence of chemical change
- change in colour
- change in odour
- formation of precipitate (solid)
- gas is made (bubbles=proof)
- release/absorption of heat energy
reactant
materials at the start (“ingredients”)
LEFT
product
new materials that are made/produced
RIGHT
exothermic reaction
releases heat (“ex” = exit)
makes the surroundings feel HOT
ex. burning anything
endothermic reactions
absorbs heat (“en” = enter)
makes the surroundings feel COLD
ex. ice pack
5 types of chemical reactions
formation
decomposition
single replacement
double replacement
hydrocarbon combustion
formation reactions
two elements come together to make a compound
decomposition reaction
Compound breaks apart to become two separate element atoms
single replacement reaction
A compound and element combine. The lone element replaces one of the elements in the compound
AB + C becomes AC + B
double replacement reaction
2 compounds swap their elements with each other to end up with two new compounds
AB + CD becomes AD + BC
hydrocarbon combustion reaction
HYDROCARBON (compound with hydrogen and carbon) burns in oxygen to make carbon dioxide and water vapour (and energy!)
LAW OF CONSERVATION OF MASS
Matter is NOT created or destroyed in a chemical reaction!
TOTAL MASS REACTANTS = TOTAL MASS PRODUCTS
ONLY WORK IN A CLOSED SYSTEM
RATE OF REACTION
how quickly the reaction happens
