Chemistry Review 2025

Which is Chemical Equation is Balanced?

• CH₄+O₂------CO₂+2H₂O
• H₂+O₂-----2H₂O₄
• 4Al+3O₂-----2Al₂O₃

Tags

NGSS.MS-PS1-5

A student heated a 10 gram sample of a chemical in an open container. A chemical reaction occurred, and the mass of the sample was measured again. The mass of the sample was found to be less than before the reaction. Which of the following best explains the decrease in mass of the sample?

• The heat caused the chemical to become less dense.

• The reaction gave off more heat than was added.

• Some of the lighter particles were destroyed.

• Some of the particles escaped as a gas formed.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

If reaction starts with 20g of reactants it should produce 

• a total of 40g of products
• a total of 10g of products
• a total of 80 g of products
• a total of 20g of products

Tags

NGSS.MS-PS1-5

Which of the models of a chemical reaction best represents the Law of Conservation of Mass?

• A

• B

• C

• D

Tags

NGSS.MS-PS1-5

A student pours hydrochloric acid (HCl) into an open beaker that contains a piece of magnesium (Mg). A chemical reaction occurs, and the data for the reaction is shown in the image. Was there a total mass increase or a total mass decrease for this experiment?

• There was a increase in mass.

• There was a decrease in mass.

• There was no change in mass.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A student dissolved 25 grams of salt into 1,000 grams of water. What should the mass of the saltwater mixture be?

• 975 grams

• 1,000 grams

• 1,025 grams

• 2,500 grams

Tags

NGSS.MS-PS1-5

Mark is observing a burning candle.  He notices that the candle wax makes a pool and dribbles down the side of the candle, where it hardens again.  The wax has undergone:

• a physical change

• a chemical change

• a physical and chemical change

• the formation of a new substance

Tags

NGSS.MS-PS1-2

Which of the following is an example of a physical change?

• sugar and oxygen reacting to produce water and carbon dioxide
• honey dissolving in tea
• a raw egg being cooked
• metal rusting after being left out in the rain

Check all that is a chemical change.

• Tearing paper

• Bubbles after mixing two unknown substances

• Food digesting

• Water boiling

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following chemical formulas represents a compound? 

• C₃
• O₂
• CH₃CHO
• H₂

Tags

NGSS.MS-PS1-1