Chemical Reactions Lesson

Based on our discussion in class, which of these is a chemical equation that demonstrates the combination (synthesis) atoms of multiple substances?

• 2H₂O -> 2H₂ + O₂

• 2H₂O₂ -> 2H₂O + O₂

• 4Fe + 3O₂ -> 2Fe₂O₃

• Pb(NO₃)2 + 2KI -> PbI₂ + 2KNO₃

Tags

NGSS.MS-PS1-5

The law of conservation of matter states

• matter cannot be created or destroyed.

• matter that is created can be destroyed.

• matter can be created, but cannot be destroyed.

• matter cannot be created, only destroyed.

Tags

NGSS.MS-PS1-5

How does burning charcoal function as a hand warmer?

• You can place your hand over burning charcoal similar to warming your hands at a fire.

• The exothermic reaction of placing charcoal on fire is so weak that you can pick up the

  coal.

• The exothermic reaction of burning charcoal placed in a pouch can last for several hours.

• The endothermic reaction of charcoal draws heat from your hands and generates energy.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-3

How does iron powder function as a hand warmer?

• The iron and the oxygen in the air mix, causing an exothermic reaction.

• Iron powder mixed with water causes an exothermic reaction.

• Iron powder has a low melting point, so it easily produces heat.

• The heat from rubbing your hand causes an exothermic reaction with the iron.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-4

Which of these is NOT true of endothermic reactions? Endothermic reactions:

• store energy.

• absorb more heat than they release.

• require a constant source of energy.

• release more heat than they absorb.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

What effect does a continuous source of energy have on the reactants in an endothermic reaction?

• The endothermic reaction causes the reactants to continue to grow in size.

• The reactants keep changing into products during the reaction.

• The bonds between the atoms of reactants in an endothermic reaction soften.

• The number of atoms in the reactants increases during an endothermic reaction.

Tags

NGSS.MS-PS1-4

Two samples a colorless liquid that melts at 12°C and a yellow solid that melts at 390°C are mixed together. One of the ending substances was a gray solid. The ending substance, made up of repeating group of atoms, are shown above. Which of the diagrams (answers) shows the repeating groups of atoms that make up the samples he mixed together? (Remember, when new substances form the reactants rearrange to form different products with the same atoms.)

• 
• 
• 
• 

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A company needs to create frying pans with a high melting point. To create this new substance, workers mixed together two substances in a sealed container. The diagram above shows the repeating groups of atoms that make up the two starting substances that melt at higher temperatures in the sealed container. (Nothing had escaped.)

Which of the diagrams to the left shows the repeating groups of atoms that make up the ending substances? (Remember, atoms on the reactant side of the equation, must be on the product side in the same amount but rearranged to form a new substance.)

• 
• 
• 
• 

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Asia mixed two samples together: a white solid that boils at 800°C and a colorless gas that boils at 70°C. She analyzed the results and found two ending substances. One of the ending substances boils at 245°C. This ending substance is made up of the repeating group of atoms shown above. Which of the diagrams(answers) shows the repeating groups of atoms that make up the samples the scientist mixed together?

• 
• 
• 
• 

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Tyler is working at a company that makes ink. To make a new kind of ink, Tyler mixed two liquid substances together in a sealed container. The diagram above shows the repeating groups of atoms that make up the two starting substances.

After mixing, he found two solid substances in the sealed container. (Nothing had escaped.) Which of the diagrams (answers) shows the repeating groups of atoms that make up the ending substances? (Remember when a chemical reaction occurs the atoms rearrange to form a new substance.)

• 
• 
• 
• 

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5