Chemical Reactions

Question 1

Distinguishing Between Physical and Chemical Changes:

Answer 1

Physical changes involve a change in appearance, state, or form of matter without altering its chemical composition. Chemical changes involve the formation of new substances with different chemical properties.

Question 2

Definition of a Chemical Reaction:

Answer 2

A chemical reaction is a process in which one or more substances (reactants) are converted into one or more different substances (products), with the formation of new chemical bonds and the rearrangement of atoms.

Question 3

Word Equation of Reactions of Metals with Oxygen, Acid, and Water:

Answer 3

Metal + Oxygen → Metal Oxide
Metal + Acid → Salt + Hydrogen gas
Metal + Water → Metal Hydroxide + Hydrogen gas

Question 4

Signs/Indicators of a Chemical Reaction:

Answer 4

Formation of gas, change in color, formation of precipitate (solid), release or absorption of heat or light, and production of odor.

Question 5

Salts Produced with Acid and Metal Reactions:

Answer 5

Salts produced depend on the metal and acid involved in the reaction, such as zinc chloride, copper sulfate, or magnesium nitrate.

Question 6

Reactivity Series of Metals:

Answer 6

A list of metals arranged in order of their reactivity, with the most reactive metals at the top and the least reactive at the bottom.

Question 7

Displacement Reaction:

Answer 7

A displacement reaction occurs when a more reactive element displaces a less reactive element from its compound.

Question 8

Single Displacement Reactions Between Metal and Metal Oxides:

Answer 8

Metal + Metal Oxide → Metal Oxide + Metal

Question 9

Predicting Reactions Using the Reactivity Series:

Answer 9

A metal higher in the reactivity series can displace a metal lower in the series from its compound.

Question 10

Factors Increasing the Rate of Reaction:

Answer 10

Temperature, concentration of reactants, surface area, presence of catalysts, and pressure (for gaseous reactions).

Question 11

Activation Energy:

Answer 11

The minimum amount of energy required for a chemical reaction to occur.

Question 12

Endothermic and Exothermic Reactions:

Answer 12

Endothermic reactions absorb heat from the surroundings, while exothermic reactions release heat to the surroundings.

Question 13

Examples of Endothermic and Exothermic Reactions:

Answer 13

Endothermic: Melting ice, evaporation of water, and baking soda reacting with vinegar.
Exothermic: Burning wood, rusting of iron, and neutralization reactions.

Question 14

Interpreting Reaction Profiles, Calculating ΔH, and Determining Endo/Exothermic Reactions:

Answer 14

Endothermic reactions have a positive change in enthalpy (ΔH), while exothermic reactions have a negative ΔH. Reaction profiles show the energy changes during a reaction.

Question 15

Bond Breaking and Bond Forming:

Answer 15

Breaking bonds requires energy and is endothermic, while forming bonds releases energy and is exothermic.

Question 16

Effects of Catalysts on Rates of Reaction - Using Elephant’s Toothpaste:

Answer 16

Catalysts speed up chemical reactions by providing an alternative reaction pathway with a lower activation energy. In the breakdown of hydrogen peroxide, a catalyst like potassium iodide (KI) or yeast is used to catalyze the decomposition of hydrogen peroxide into water and oxygen, producing foam (elephant’s toothpaste).