Unit 2 - Chemical Reactions

Question 1

What is a chemical reaction?

Answer 1

When one or more substances changes into one or more new substances

Question 2

What happens during a physical change?

Answer 2

The properties of the substances may change but the identity stays the same (ice cream melts, still an ice cream)

Question 3

What are the evidence of a chemical reaction?

Answer 3

• Formation of gas
• Formation of a precipitate
• Change in colour
• Change in odour
• Change in temp
• Production of light

Question 4

What is an endothermic reaction?

Answer 4

Occurs when it takes more energy to break the bond (absorb energy)

Question 5

What is an exothermic reaction?

Answer 5

When it takes more energy to form the bond (will release energy)

Question 6

What is the law of conservation of mass?

Answer 6

Matter cannot be created or destroyed in a chemical reaction (mass of reactants=mass of products)

Question 7

What are acids?

Answer 7

Compounds with H, <7

Question 8

What are bases?

Answer 8

Compounds with OH, >7

Question 9

What is synthesis

Answer 9

2 reactants form 1 larger product

Question 10

What is an oxide?

Answer 10

Compound with oxygen

Question 11

What are oxysalts?

Answer 11

Metal oxides react with non metal oxides –> combine them (Na2O+CO2 –> Na2CO3

Question 12

What is decomposition?

Answer 12

Break down of the larger compound (opposite of synthesis)

Question 13

What is a single displacement reaction?

Answer 13

When one element replaces an element in a compound

Question 14

What is a metal/halogens activity series?

Answer 14

Lists elements according to their observed reactivity in single displacements.

If the element trying to replace another is lower, the reaction will not occur

Question 15

What is dissociation?

Answer 15

When the crystal lattice is pulled apart by water molecules

Question 16

What is a double displacement reaction?

Answer 16

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

Question 17

What is a neutralization reaction?

Answer 17

The reaction of an acid and a base to form a mixture with a pH of 7

Question 18

What is a combustion reaction?

Answer 18

When a substance reacts with oxygen gas to produce light and heat (common is hydrocarbons)

Question 19

What is an incomplete combustion?

Answer 19

When there is limited supply of oxygen

Question 20

What is a metal combustion?

Answer 20

Producing metal oxides

Question 21

What are applications of neutralization?

Answer 21

• 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