Classifying Matter Assessment Period 6

Directions: Select ONE of the following prompts below to write your five-paragraph essay response. Put a star next to the one you choose. Please use complete sentences in your response and answer all parts of the question. You must include all components of the paragraph for each section to receive full credit.

Prompt Options: 

1. Is salt water a pure substance or a mixture? Is it homogeneous or heterogeneous? Defend your answer using microscopic and particle-level evidence. 
2. Is carbon dioxide (CO₂) a mixture or a pure substance? Is it an element or a compound? Defend your classification using microscopic evidence. 
3. Is pancake batter a homogeneous mixture, heterogeneous mixture, or a pure substance? Defend your answer using particle-level reasoning. 

Use this checklist to support your writing: 

• Define key terms 
• Classify your substance correctly 
• Use particle or microscopic level reasoning to defend your answer 
• Use sentence stems as needed
• Use 3-4 vocabulary words from the checklist

Vocabulary Checklist (use at least 3-4 words) 

☐ atom            ☐ molecule

☐ bonded        ☐ uniform

☐ fixed ratio   ☐ physically separated

☐ chemically combined

Paragraph 1 - Introduction + Claim

• Explain how matter is classified 
• Introduce the substance. 
• Clearly state your classification (two parts if needed).

Sentence Stems:

• Matter is classified based on __________ and __________.
• Scientists classify substances by looking at __________.
• __________ should be classified as a __________ because __________.
• In this essay, I will prove that __________ is a __________ using particle-level evidence.

Paragraph 2 - Classification Decision (Pure Substance vs Mixture; Element vs Compound; Homogeneous vs Heterogeneous) 

• Define both categories being considered. 
• Apply the definition to your substance.
• Use particle-level reasoning.  
• Explain atom types. 
• Reference formulas if applicable.

Sentence Stems: (You will not need this many sentences!)

• A pure substance is __________, while a mixture is __________.
• In a pure substance, the composition is __________.
• In this sample, the particles are __________.
• This shows that __________ is a __________ because __________.
• At the microscopic level, we observe __________.
• An element is made of __________.
• A compound contains __________.
• A homogeneous mixture looks __________ throughout.
• A heterogeneous mixture has __________.
• The formula __________ shows that __________.
• Because there are __________ types of atoms, this must be a __________.

Paragraph 3 - Comparison or Counterexample 

• Compare your substance to something clearly different. 
• Explain how particle structure differs.

Sentence Stems:

• This is different from __________ because __________.
• In contrast, __________ contains __________.
• Unlike __________, this substance has __________.
• If it were a __________, then we would expect __________.

Paragraph 4 - Conclusion

• Restate your classification.
• Use microscopic vocabulary.
• Reaffirm your evidence.

Sentence Stems:

• Based on the particle evidence, __________ is classified as __________.
• The atoms are __________, which proves __________.
• Because the composition is __________, it cannot be a __________. Therefore, __________ must be classified as __________.