Chemical Equations Video Lesson

What is the smallest unit of matter?

• Element

• Atom

• Atomic particles

• Protons

Answer explanation

Although atoms are made up of smaller particles, called subatomic particles (protons, neutrons, and electrons), atoms are the smallest unit of matter that retains the properties of an element.

What is unique about each element?

Each element has a unique number of _______.

Answer explanation

Every element has a specific number of protons. No element has the same number of protons.

How are molecules and compounds different?

• All molecules are compounds.

• Compounds are made up of two or more atoms of the same element. Molecules are made up of the same or different elements.

• There is no difference; they are the same.

• Compounds consist of atoms of different elements, while molecules can have atoms of the same or different elements.

Answer explanation

Molecules form when two or more atoms join together. All compounds are molecules. Compounds are unique because they must be formed from two or more different elements.

Here are some examples of molecules:

H₂

O₃

H₂O

Here are some examples of compounds:

H₂O

NaCl

FeO

Al₂O₃

Is OH a compound or a single element?

• Compound

• Single element

Answer explanation

OH is a compound made from Oxygen (O) and Hydrogen (H).

How can you tell if OH is a compound or a single element based on the element symbols?

• It’s a single element because it only has two letters.

• It’s a single element because it’s found on the periodic table.

• It’s a compound because both "O" and "H" are capital letters.

• It’s a compound because it has one capital letter and one lowercase letter.

Answer explanation

We can tell it is made up of 2 elements because there are two capital letters. When element symbols only consist of 1 letter, it is always captialized. When element symbols have two letters, the first is capitalized, the second is not.

OH = 2 elements formed from a bond between O and H

Na, Cl, Au, and Fe are all examples of two-letter single element symbols. Notice how the first letter is capitalized and the second letter is not?

Which of these options is a singular element?

• NaCl

• H₂O

• OH

• Fe

Answer explanation

Fe is the singular element. We know because the second letter is lowercase, indicating that it is not an element symbol on its own.

Fe is the element symbol for iron.

Which of these is a molecular compound with 2 elements?

• O₂

• KOH

• NaCl

• K₃PO₄

Answer explanation

NaCl is a 2 element molecular compound. It is formed from Na (sodium) and Cl (chlorine).

O₂ is not a compound because it is made from only one element, oxygen.

KOH and K₃PO₄ both are made up of 3 elements each.

How many atoms of each element do we have in the example: 3Al₂O₃?

• Al: 3

  O: 2

• Al: 6

  O: 3

• Al: 5

  O: 6

• Al: 6

  O: 9

Answer explanation

To determine how many atoms of each element we have, we need to multiply the coefficient by the subscript.

3Al₂O₃

3 is our coefficient.

Al has a subscript of 2

(3 * 2) = 6 Al atoms

3 is our coefficient.

O has a subscript of 3

(3 * 3) = 9 O atoms

How many atoms of each element are there in this example 2NaHCO₃?

• Na: 2

  H: 2

  C: 2

  O: 6

• Na: 2

  H: 1

  C: 1

  O: 3

• Na: 2

  H: 1

  C: 1

  O: 6

• Na: 2

  H: 1

  C: 1

  O: 3

Answer explanation

In the compound, 2NaHCO₃, we have a coefficient of 2. That means we have to multiply 2 by each element's subscript.

Na, H and C don't have a written subscript. That means we will multiply the coefficient 2, by 1 to find the number of atoms of each.

Na: 2

H: 2

C: 2

O has a subscript of 3. So we multiply 2*3 to get 6 atoms of oxygen.

O:6

What do both sides of a chemical equation have to have to make a balanced equation?

The same number of _____ of each element on both sides of the yield arrow.

Answer explanation

Because the Law of Conservation of Matter states that matter cannot be created or destroyed in a chemical reaction, there must be the same number of atoms of each element in reatants and the products.