Phy Sci 6ed Chap 7 Review

Is a change in size a chemical or physical change?

• physical

• chemical

• neither

Answer explanation

change in size typically is associated with thermal expansion or contraction, which would not change the substance

Which of the following is the correct balance chemical equation for the following word equation:

potassium reacts with chlorine to produce potassium chloride

• 2K + Cl₂ → 2KCl

• K + Cl → KCl

• KCl → K + Cl

• K + Cl₂ → KCl₂

Which of the following is not a unit of measurement, but is a quantity similar to "a dozen"

• kilogram

• mole

• milliliter

• electronegativity

Answer explanation

1 mol = 6.022 x 10²³ units, although typically the units being counted are tiny particles

How many moles of potassium are needed to react with 1 mole of chlorine according to the following equation:

2K + Cl₂ → 2KCl

• 2 mol K for 1 mol Cl₂

• 2 mol K for 2 mol of Cl₂

• 1 mol K for 1 mol Cl₂

• Impossible to tell

What kind of react shows both reactants and products include only an element on it's own and a compound

• single-repalcement

• double-replacement

• synthesis

• combustion

What do we call the kind of reaction where one element loses electrons and the other element gains electrons?

• electron exchange reaction
• redox reaction
• electron transfer reaction
• oxidation-addition reaction

What is required in a combustion reaction?

• Fuel, oxygen, and heat
• Fuel and heat only
• Fuel, oxygen, and water
• Fuel and oxygen only

Answer explanation

every combustion reaction requires a fuel, oxygen, and heat, and produces carbon dioxide and water

An oxidation reaction occurs when

• There is a loss of electrons from a substance.
• There is a gain of protons in a substance.
• There is a gain of electrons from a substance.
• oxygen takes electrons from an element

Answer explanation

oxidation does NOT require the presence of oxygen, any element that loses electrons in a reaction is oxidized, regardless of whether oxygen is the agent doing the oxidizing and being reduced, or whether a different element is playing that role.

What happens to the energy given off by a campfire?

• some energy is absorbed by the environment

• some energy is given off as light energy

• some energy is given off as thermal energy

• all of the options are true of energy given off by a campfire

Answer explanation

remember that energy, like matter, can never be created or destroyed, only changed in form

How does a catalyst increase a reaction rate?

• By changing the chemical composition of the reactants.
• By increasing the activation energy required for the reaction to occur.
• By slowing down the reaction rate.
• By lowering the activation energy required for the reaction to occur.