Chemistry--balancing equations

Which describe reactants?

• They are the substances that exist before the reaction

• They are the substances that exist after the reaction

• They appear on the left side of the equation

• They appear on the right side of the equation

Which describe products

• They are the substances that exist before the reaction

• They are the substances that exist after the reaction

• They appear on the left side of the equation

• They appear on the right side of the equation

A subscript tells

• the charge.

• the number of atoms (or group of atoms, if in parentheses).

• how many molecules are present.

• the number of protons.

Coefficients are

• the large numbers that go in front of a chemical formula; they indicate how many moles or molecules/formula units are present.

• the large numbers that go in front of a chemical formula; they indicate the charge.

• the small dropped numbers inside a formula; they indicate how many of that atom is present in a molecule.

• the small dropped numbers inside a formula; they indicate how many moles or molecules/formula units are present.

Why do we balance equations?

• For math practice

• Because the same number of atoms are present before and after a reaction--they are just rearranged.

• To show how many atoms are lost or gained during a reaction.

• To see whether the chemical reaction is possible.

Tags

NGSS.MS-PS1-5

Which is true of phase notations?

• Up arrow means gas product

  Down arrow means solid product

  Arrows both directions mean reversible reaction

  Triangle under arrow means heated reaction

• Up arrow means gas reactant

  Down arrow means solid reactant

  Arrows both directions mean reversible reaction

  Triangle under arrow means heated reaction

• Up arrow means gas product

  Down arrow means solid product

  Arrows both directions mean reversible reaction

  Triangle under arrow means combustible reaction

• Up arrow means gas product

  Down arrow means solid reactant

  Arrows both directions mean failed reaction

  Triangle under arrow means combustible reaction

What is notable about the following?

F2     H2     N2    Br2    O2     Cl2     I2

• They are diatomic molecules. They exist in pairs in nature.

• They have the same number of protons.

• They have charges of +2.

• They are diatomic molecules. They exist in pairs only in the lab.

1. Identify which substances are reactants and which are _____.

Tags

NGSS.MS-PS1-2

• 2. Write correct _______ for each substance

Tags

NGSS.MS-PS1-1

• 3. 3. Copy the chemical formulas for the reactants on a new line and draw a reaction _____ that points right.