Concept Refresher

Which of the following is an example of a molecule?

• A) a group of atoms bonded together

• 
• All of the above

What is the Law of Conservation of mass?

• Mass is created in a chemical reaction

• Mass is created in a physical change

• New chemicals formed from a chemical reaction have a larger overall mass than the original reactants

• Mass is never created or destroyed

The Coefficient (3) in the Chemical Formula, 3H₂O, tells you how many _____________ there are.

• Atoms of Hydrogen

• Atoms of Oxygen

• Atoms of Water

• Molecules of Water

The Subscript (2) in the Chemical Formula, 3H₂O, tells you how many _____________ there are.

• Atoms of Hydrogen

• Atoms of Oxygen

• Atoms of Water

• Molecules of Water

What is the law of conservation of mass?

• The amount of matter changes when reacted or changed.

• The mass of all reactants are changed during a physical or chemical change

• The mass of the reactants equals the mass of the products

• The mass of the products is different than the mass of the reactants.

Why must the number of each type of atom on the reactant side equal the number of each type of atom on the product side?

• This means the mass of the reactants equals the mass of the products, which follows the law of conservation of mass.

• This means that the mass of the reactants equals the mass of the products, which does not follow the law of conservation of mass.

The number in front of a compound or element is a

(for example: the item labeled "A" on the image attached)

• Subscript

• Coefficient

• Superscript

• Charge

The number to the lower side of an element is a

(for example: the item labeled "B" on the image attached)

• Subscript

• Superscript

• Coefficient

• Charge

Matter can not be created nor destroyed: it can only be

• Destroyed a little bit

• Invisible

• Transformed, changed, rearranged into a different form

• None of the above

A chemical reaction is balanced when

• both sides have the same elements

• Both sides have the same  number of atoms

• Same subscripts

• Same coefficients