STAAR Chemistry Review Day 2

Multiple Choice

What cannot be broken down into other substances?

• Compound

• Element

Multiple Choice

What is made up two or more elements that are chemically combined?

• Element

• Mixture

• Compound

• Solids

What would the
chemical formula be
for 1 atom of
Helium?

What would the
chemical formula be
for 2 atoms of
oxygen?

What would the chemical
formula be for 2 atom of
hydrogen bonded with 1
atom of oxygen?

1 atom of

Helium = He

2 atoms of

Oxygen

= O₂

2 atoms of Hydrogen

+ 1 atom Oxygen

= H₂O

What do you notice is different about the
formula for the compound vs the formulas

for the elements?

1 atom of

Helium = He

2 atoms of

Oxygen

= O₂

2 atoms of Hydrogen

+ 1 atom Oxygen

= H₂O

Elements have 1 capital letter in their symbol.

Compounds have 2 or more DIFFERENT capital letters.

Multiple Select

Which two of these are elements?

• Water (H₂O)

• Hydrogen (H₂)

• Salt 🧂 (NaCl)

• Iron (Fe)

• Carbon dioxide (CO₂)

Multiple Select

Which two of these are compounds?

• Au

• Cl

• NaCl

• CO2

Multiple Choice

Which of the following represents an element?

• H₂O

• H₂

• NaCl

• CaCO₃

Multiple Choice

How many elements are in C₆H₁₂O₆?

• 1

• 2

• 3

• 4

Multiple Choice

How many atoms of Carbon are in this formula? $$C_{6\ }H_{12}O_6$$  

• 6

• 1

• 12

Multiple Choice

What is the total number of atoms in this formula? $$H_2O_2$$  

• 2

• 4

• 3

Multiple Choice

How many Hydrogen are in 4H₂O?

• 6

• 8

• 2

• 4

Multiple Choice

How many Sodium (Na) are in 6NaCl?

• 1

• 12

• 6

Multiple Choice

How many O's are in Al₂(SO₄)₃

• 4

• 12

• 7

• 24

Multiple Choice

Number of H in 3(NH₄)₂CrO₄

• 4

• 2

• 8

• 24

Law of Conservation of Mass

➢

Chemical Equations, like above, must be balanced.
Meaning, if you start with 1 atom of carbon on the

reactant side, you should end with 1 atom of carbon on

the product side.

Let’s check if this chemical equation is

balanced or unbalanced.

Multiple Choice

Is this equation balanced?

HCl + NaOH --> NaCl + H₂O

• yes

• no

Multiple Choice

Is this equation balanced?

H₃PO₄ + KOH --> K₃PO₄ + H₂O

• yes

• no

Unexpected Color Change

Light

Evidence of Chemical Change

Gas

Unexpected

Temperature Change

Odor (smell)
Precipitate

Multiple Choice

Which of the following is an example of physical change?

• Mixing baking soda and vinegar together, and this causes bubbles and foam.

• A glass cup falls from the counter and shatters on the ground.

• Lighting a piece of paper on fire and the paper burns up and leaves ashes.

• Baking a birthday cake for your mother.

Multiple Choice

Which of the following is an example of chemical change?

• Filling up a balloon with hot air.

• Taking a glass of water and freezing it by placing it in the freezer.

• A plant collecting sunlight and turning it into food.

• Your dog ripping up your homework.

Multiple Choice

When a new substance is formed with different properties than the original substance it is called a

• Chemical change

• Physical change

• Freezing

• Boiling

Multiple Choice

Which is an example of a physical change?

• Metal rusting

• Silver tarnishing

• Water boiling

• Paper burning

Multiple Choice

Which is an example of chemical change?

• Water freezes

• Wood is cut

• Bread is baked

• Wire is bent

Multiple Choice

Which is not a clue that could indicate a chemical change?

• Change in color

• Change in shape

• Change in energy

• Change in odor

Multiple Choice

When you swallow your food and the food is then getting digestive in stomach acid and different enzymes, that is considered___________.

• mechanical digestion

• chemical digestion