Unit 2 - Chemical Reactions Flashcards
What is a chemical reaction?
When one or more substances changes into one or more new substances
What happens during a physical change?
The properties of the substances may change but the identity stays the same (ice cream melts, still an ice cream)
What are the evidence of a chemical reaction?
- Formation of gas
- Formation of a precipitate
- Change in colour
- Change in odour
- Change in temp
- Production of light
What is an endothermic reaction?
Occurs when it takes more energy to break the bond (absorb energy)
What is an exothermic reaction?
When it takes more energy to form the bond (will release energy)
What is the law of conservation of mass?
Matter cannot be created or destroyed in a chemical reaction (mass of reactants=mass of products)
What are acids?
Compounds with H, <7
What are bases?
Compounds with OH, >7
What is synthesis
2 reactants form 1 larger product
What is an oxide?
Compound with oxygen
What are oxysalts?
Metal oxides react with non metal oxides –> combine them (Na2O+CO2 –> Na2CO3
What is decomposition?
Break down of the larger compound (opposite of synthesis)
What is a single displacement reaction?
When one element replaces an element in a compound
What is a metal/halogens activity series?
Lists elements according to their observed reactivity in single displacements.
If the element trying to replace another is lower, the reaction will not occur
What is dissociation?
When the crystal lattice is pulled apart by water molecules
What is a double displacement reaction?
When elements in 2 compounds trade places to produce 2 new compounds.
Rule - One compound must precipitate (in the products side) for the reaction to occur
What is a neutralization reaction?
The reaction of an acid and a base to form a mixture with a pH of 7
What is a combustion reaction?
When a substance reacts with oxygen gas to produce light and heat (common is hydrocarbons)
What is an incomplete combustion?
When there is limited supply of oxygen
What is a metal combustion?
Producing metal oxides
What are applications of neutralization?
- Stomach acid (HCl) that leaks upward out of the stomach into the esophagus can cause irritation (“heartburn”)
- Emissions of sulfur oxides and nitrogen oxides combine with rain to form acid rain
- Organisms that live in bodies of water can only tolerate small reductions in the pH of their water
- In Southern Ontario, the rock bed is mainly calcium carbonate (limestone), but in Northern Ontario, the rock bed is mainly granite
- A temporary solution is “liming” a lake by adding calcium oxide to it
