classifying matter worksheet key - Worksheet: Classification of ... - Free Printable

Let’s go step by step to solve this worksheet.

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Part I: Fill in the Blanks

We’ll read each sentence and fill in the correct term based on chemistry basics.

1. An _element_ is a pure substance consisting of atoms of only one kind of atom.
→ Elements are made of just one type of atom (like gold, oxygen, etc.).

2. The symbol for an element is always written with the first letter capitalized; when the symbol contains two letters, the second letter is always lowercase.
→ Example: “H” for hydrogen, “He” for helium — never “HE”.

3. An _compound_ is a pure substance containing two or more elements that are chemically combined. A compound is represented by a chemical formula showing the number of atoms of each element contained in it.
→ Like H₂O — water has 2 hydrogen and 1 oxygen atom.

4. A _mixture_ is a physical blend of two or more substances that are not chemically combined. The components of a mixture retain their own properties and can be separated by physical means.
→ Like salt and sand mixed together — you can separate them by dissolving salt in water.

5. A mixture that has a uniform composition throughout is called _homogeneous_.
→ Like saltwater — looks the same everywhere.

6. A mixture that does not have a uniform composition throughout is called _heterogeneous_.
→ Like salad or trail mix — you can see different parts.

7. A homogeneous mixture is also known as a solution.
→ Sugar dissolved in water = solution.

8. An example of a homogeneous mixture is air; an example of a heterogeneous mixture is soil.
→ Air is evenly mixed gases. Soil has rocks, dirt, bugs — not even.

9. Matter is anything that has mass and occupies space.
→ Basic definition of matter.

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Part II: Classify Each Substance

We need to label each as:
- E = Element
- C = Compound
- HO = Homogeneous Mixture (Solution)
- HE = Heterogeneous Mixture

Let’s go one by one:

1. sodium chloride → NaCl → made of sodium + chlorine chemically bonded → C
2. oxygen gas → O₂ → only oxygen atoms → E
3. sand → mixture of tiny rocks, shells, etc. → not uniform → HE
4. salt water → salt dissolved in water → uniform → HO
5. glucose → C₆H₁₂O₆ → specific chemical formula → C
6. carbon dioxide → CO₂ → fixed ratio of carbon and oxygen → C
7. sugar → usually sucrose (C₁₂H₂₂O₁₁) → compound → C
8. air → mixture of nitrogen, oxygen, etc. → uniform → HO
9. table salt → same as sodium chloride → C
10. tap water → water + minerals/chlorine → but still uniform → HO
11. potassium → K → single element → E
12. brass → alloy of copper and zinc → uniform metal mixture → HO
13. graphite → form of carbon → pure element → E
14. gold → Au → pure element → E
15. oil → if alone, it’s a compound (like hydrocarbons), but often refers to crude oil which is a mixture → However, in basic chem, “oil” is treated as a compound unless specified. But wait — actually, most oils (like vegetable oil) are mixtures of triglycerides → so HO? Hmm… Let’s think: In many textbooks, “oil” is considered a homogeneous mixture because it’s a blend of similar molecules. But sometimes it’s called a compound. Actually, pure olive oil is a mixture of different fats → so HO.
- Correction: Since it’s not a single chemical formula, and varies → HO
16. ice → frozen water → H₂O → compound → C

Wait — let’s double-check tricky ones:

- Brass: Definitely homogeneous mixture (alloy).
- Oil: If it’s cooking oil or motor oil, it’s a mixture → HO
- Ice: Still H₂O → compound → C

Final classification:

1. sodium chloride → C
2. oxygen gas → E
3. sand → HE
4. salt water → HO
5. glucose → C
6. carbon dioxide → C
7. sugar → C
8. air → HO
9. table salt → C
10. tap water → HO
11. potassium → E
12. brass → HO
13. graphite → E
14. gold → E
15. oil → HO
16. ice → C

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Final Answer:

Part I:
1. element
2. lowercase
3. compound, chemical formula
4. mixture, physical means
5. homogeneous
6. heterogeneous
7. solution
8. air, soil (or any valid examples)
9. mass, space

Part II:
1. C
2. E
3. HE
4. HO
5. C
6. C
7. C
8. HO
9. C
10. HO
11. E
12. HO
13. E
14. E
15. HO
16. C