Intro to Chemical Reactions

The picture above shows a light stick. Light sticks begin to glow when the vial inside the stick is broken. Chemicals inside the vial mix with chemicals outside of the vial. Which of the following statements BEST supports the idea that a chemical reaction, rather than a physical change, is occurring?

• The vial is broken into smaller pieces.
  
• Energy is released in the form of light.
  
• Two different substances are combined.
• The substances are in a flexible container.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which chemical equation best illustrates the law of conservation of mass?

• 2Al+CuO -> Al₂O₃ +3Cu
• 2Al+3CuO -> Al₂O₃ +Cu
• 2Al + 3CuO -> Al₂O₃ + 3Cu
• 3Al + 2CuO ->  Al₂O₃ + 2Cu

Tags

NGSS.MS-PS1-5

Some spoons are made with the element silver (Ag). Over time, these spoons will turn black if they are not cleaned with a special solution. Which of the following statements BEST explains why the element silver in the spoons turns black?

• It absorbs energy when exposed to warm food.
  
• It breaks down into smaller and smaller particles.
  
• It reacts with substances in the air to form a new substance.
  
• It changes from one phase of matter into another phase of matter.

Tags

NGSS.MS-PS1-2

Which of the following contains one oxygen atom?

• H₂O
• CO₂
• 2N₂O
• Co

Tags

NGSS.MS-PS1-1

Which process causes substances to react to form one or more new substances?

• chemical change
• physical change
• evaporation
  
• freezing

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which chemical equation correctly shows the formation of water from hydrogen and oxygen?

• H₂ +O₂ =H₂O
• 2H₂ +O₂ =2H₂O
• H₂ +2O=H₂O
• H+O₂ =H₂O

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-5

A scientist carries out a reaction in a test tube. After the bubbling stops, she notices that the test tube is very warm. What might she conclude about the reaction?

• The reaction happened very quickly.
• The reaction is endothermic.
• The reaction is exothermic.
• No reaction took place.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-5

A substance that is used to speed up a chemical reaction is called

• a reactant.
• an inhibitor.
• a precipitate.
• a catalyst.

During a laboratory experiment, Tran applied the law of conservation of energy. Which of the following did he assume to be true?

• Energy is not changed.
• Energy is not created or destroyed.
• The total energy of the reactants is greater than the total energy of the products.
• The total energy of the reactants is less than the total mass of the products.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-1

NGSS.HS-PS3-2

NGSS.HS-PS3-4