7.7-2.4: Chemical Reactions Critical Juncture Assessment

The diagram above shows the repeating groups of atoms that make up two samples. Will the properties of the two samples likely be the same or different? (Examples of properties are smell, color, and the temperature at which a substance melts.)

• The properties will likely be different because there are more repeating groups of atoms in Sample 2.

• The properties will likely be different because the repeating groups of atoms that make up each sample are different.

• The properties will likely be the same because the repeating groups of atoms that make up the two samples have one of the same types of atoms.

• The properties will likely be the same because the repeating groups of atoms that make up the two samples have the same number of atoms.

Tags

NGSS.MS-PS1-1

A scientist mixed two samples together: a colorless liquid that melts at 12°C and a yellow solid that melts at 390°C. She analyzed the results and found two ending substances. One of the ending substances was a gray solid. This ending substance is made up of the repeating group of atoms shown above. Which of the diagrams to the left shows the repeating groups of atoms that make up the samples the scientist mixed together?

• 
• 
• 
• 

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The diagram above shows the repeating groups of atoms that make up two samples. Both samples are gases at room temperature. Will the other properties of the samples likely be the same or different? (Examples of properties are smell, color, and the temperature at which a substance melts.)

• The other properties will likely be the same because the repeating groups of atoms that make up the two samples have the same types of atoms.

• The other properties will likely be the same because both samples are gases at room temperature.

• The other properties will likely be different because there are more repeating groups of atoms in Sample 1.

• The other properties will likely be different because the repeating groups of atoms that make up the two samples have different numbers of atoms.

Tags

NGSS.MS-PS1-1

A scientist mixed two samples together: a white solid that boils at about 800°C and a colorless gas that boils at about 70°C. He 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 to the left shows the repeating groups of atoms that make up the samples the scientist mixed together?

• 
• 
• 
• 

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

The diagram above shows the repeating groups of atoms that make up two samples. Both samples are solids at room temperature. Will the other properties of the two samples likely be the same or different? (Examples of properties are smell, color, and the temperature at which a substance melts.)

• The other properties will likely be different because there are more repeating groups of atoms in Sample 2.

• The other properties will likely be different because the repeating groups of atoms that make up the two samples have different numbers of atoms. 

• The other properties will likely be the same because the repeating groups of atoms that make up the two samples have the same types of atoms.

• The other properties will likely be the same because both samples are solids at room temperature.

Tags

NGSS.MS-PS1-1

Jacob mixed two samples together: a colorless gas with no smell and a colorless liquid that smells like bleach. He analyzed the results and found two ending substances. One of the ending substances was a green gas. This ending substance is made up of the repeating group of atoms shown above. Which of the diagrams to the left shows the repeating groups of atoms that make up the samples Jacob mixed together?

• 
• 
• 
• 

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The diagram above shows the repeating groups of atoms that make up two samples. Both samples are red powdery solids at room temperature. Will the other properties of the two samples be the same or different? (Examples of properties are smell, color, and the temperature at which a substance melts.)

• The other properties will be different because there are more repeating groups of atoms in Sample 1.

• The other properties will be the same because both samples are red at room temperature.

• The other properties will be the same because both samples are powdery solids at room temperature.

• The other properties will be same because the repeating groups of atoms that make up the two samples are the same.

Tags

NGSS.MS-PS1-1

A chemist mixed two samples together: a brown solid that melts at about 1,300°C and a colorless liquid that melts at about 20°C. She analyzed the results and found two ending substances. One of the ending substances melts at about 250°C. This ending substance is made up of the repeating group of atoms shown above. Which of the diagrams to the left shows the repeating groups of atoms that make up the samples the chemist mixed together?

• 
• 
• 
• 

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Samira watched a demonstration in which a scientist combined two substances in a sealed container and analyzed the results. The ending substances did not look the same as the starting substances.

Samira was given a diagram with the repeating groups of atoms that make up the starting substances, plus information about the properties of the starting and ending substances. She created a model of the repeating groups of atoms that might make up the two ending substances.

Does her model correctly show why the properties of the ending substances are different from the properties of the starting substances? Describe what could be correct or incorrect about her model.

Pick the BEST response.

• Samira’s model correctly explains why the properties are different. It shows that there are different groups of atoms in the substances before and after mixing. The properties aren’t the same because they have different groups of atoms at the end. Therefore, they aren’t the same substances.

• Samira’s model correctly explains why the properties are different. It shows that the atoms of the starting samples rearranged to form new groups when the scientist mixed them. The atom groups Samira made in her model have some atoms from each starting sample. This shows how the atoms rearranged. The properties aren’t the same because they aren’t the same substances at the end, so the atoms must have rearranged to form different groups of atoms.

• Samira’s model has some correct and incorrect parts. It correctly shows that the properties of the substances changed because the atoms from the first two substances rearranged to form new groups. However, the model also has a mistake—it includes an orange atom in the products that wasn’t in the reactants. This is incorrect because atoms can’t just appear out of nowhere or change into a different type. Atoms can only rearrange into new groups.

  Even though Samira’s model correctly shows that the atoms from the starting substances were used to form new groups, one of the ending atoms doesn’t match any of the starting ones. Since atoms cannot just appear or disappear, this part of her model is incorrect.

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

A chemist mixed two substances together: a colorless liquid with a strong smell and a white solid with no smell. The substances’ repeating groups of atoms are shown above on the left. After they were mixed, the chemist analyzed the results and found two substances. One ending substance had the repeating group of atoms shown above on the right.

Is the ending substance the same substance as the colorless liquid? What happened to the atoms of the starting substances when the ending substances formed? Be sure to explain your answers to both of these questions.

Choose the BEST response.

• The ending substance is a different substance than the colorless liquid. It must be a different substance because the ending substance has different atoms than the colorless liquid. The purple atom turned into a black atom when the chemist mixed the colorless liquid with the white solid.

• The ending substance is a different substance than the colorless liquid. It must be a different substance because the ending substance has one atom from the colorless liquid and one atom from the white solid. A chemical reaction occurred because the orange and red atoms from the colorless liquid and the black atom from the white solid rearranged to form the repeating atom group of the ending substance.

• The ending substance is a different substance than the colorless liquid. It must be a different substance because the ending substance has one atom from the colorless liquid and one atom from the white solid. A chemical reaction occurred because the orange and red atoms from the colorless liquid and the black atom from the white solid rearranged to form the repeating atom group of the ending substance. The purple, green, and blue atoms must have combined with one another to form another atom group.

Answer explanation

5.  Key Concept

During a chemical reaction, one or more starting substances (reactants) change into one or more different substances (products).

6.  Key Concept

During a chemical reaction, atoms do not change from one type to another.

7.  Key Concept

During a chemical reaction, atoms rearrange to form different groups of atoms.

*Note - Each circle color represents a different element (type of atom)

*Note - two different substances can NOT have the exact same properties.

• *Note - If two substances are different they must be made of different elements and/or numbers of elements (So different colors and/or number of circles)

Tags

NGSS.MS-PS1-1

NGSS.MS-PS1-2

NGSS.MS-PS1-5