Educational worksheet on identifying elements, compounds, and mixtures.

Problem Overview:

The task involves understanding the definitions of elements, compounds, and mixtures and classifying given substances accordingly. The first part provides definitions and characteristics, while the second part requires classification.

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Definitions Recap:

1. Element:
- A pure substance containing only one kind of atom.
- Homogeneous (uniform throughout).
- Cannot be separated into simpler materials by physical means (except during nuclear reactions).
- Listed on the Periodic Table.

2. Compound:
- A pure substance containing two or more kinds of atoms chemically combined.
- Atoms are chemically bonded in a specific way.
- Homogeneous.
- Can be separated into its elements only by chemical reactions.
- Properties differ from those of its constituent elements.

3. Mixture:
- Two or more elements or compounds physically mixed but not chemically combined.
- No chemical reaction occurs between the components.
- Can be homogeneous (uniform) or heterogeneous (non-uniform).
- Can be separated by physical means.
- Properties are similar to those of its components.

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Part 2: Classification

We need to classify each of the following substances as an element (E), compound (C), or mixture (M). If it is none of these, we write X.

#### Substances to Classify:
1. Diamond (C)
2. Air
3. Krypton (Kr)
4. Sugar (C₁₂H₂₂O₁₁)
5. Sulfur (S)
6. Water (H₂O)
7. Alcohol (C₂H₅OH)
8. Ammonia (NH₃)
9. Salt (NaCl)
10. Wood
11. Seawater
12. Gasoline
13. Pile of Garbage
14. A dog
15. Energy
16. Iron (Fe)
17. Electricity
18. Uranium (U)
19. Popcorn
20. Gold (Au)
21. Pizza
22. Baking Soda (NaHCO₃)
23. Thorium (Th)
24. Concrete

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Classification Solution:

1. Diamond (C):
- Pure carbon (one type of atom).
- Classification: E (Element).

2. Air:
- Mixture of gases like nitrogen, oxygen, carbon dioxide, etc.
- Classification: M (Mixture).

3. Krypton (Kr):
- Pure krypton gas (one type of atom).
- Classification: E (Element).

4. Sugar (C₁₂H₂₂O₁₁):
- Chemically bonded compound of carbon, hydrogen, and oxygen.
- Classification: C (Compound).

5. Sulfur (S):
- Pure sulfur (one type of atom).
- Classification: E (Element).

6. Water (H₂O):
- Chemically bonded compound of hydrogen and oxygen.
- Classification: C (Compound).

7. Alcohol (C₂H₅OH):
- Chemically bonded compound of carbon, hydrogen, and oxygen.
- Classification: C (Compound).

8. Ammonia (NH₃):
- Chemically bonded compound of nitrogen and hydrogen.
- Classification: C (Compound).

9. Salt (NaCl):
- Chemically bonded compound of sodium and chlorine.
- Classification: C (Compound).

10. Wood:
- Complex mixture of cellulose, lignin, and other organic compounds.
- Classification: M (Mixture).

11. Seawater:
- Mixture of water, dissolved salts, and other substances.
- Classification: M (Mixture).

12. Gasoline:
- Mixture of hydrocarbons.
- Classification: M (Mixture).

13. Pile of Garbage:
- Physical mixture of various materials.
- Classification: M (Mixture).

14. A dog:
- Living organism composed of cells, tissues, and organs; not a pure substance.
- Classification: X (None of the above).

15. Energy:
- Not a substance; it is a property or form of work.
- Classification: X (None of the above).

16. Iron (Fe):
- Pure iron (one type of atom).
- Classification: E (Element).

17. Electricity:
- Flow of electrons; not a substance.
- Classification: X (None of the above).

18. Uranium (U):
- Pure uranium (one type of atom).
- Classification: E (Element).

19. Popcorn:
- Mixture of corn kernels, air, and possibly oil or seasonings.
- Classification: M (Mixture).

20. Gold (Au):
- Pure gold (one type of atom).
- Classification: E (Element).

21. Pizza:
- Mixture of dough, cheese, sauce, and toppings.
- Classification: M (Mixture).

22. Baking Soda (NaHCO₃):
- Chemically bonded compound of sodium, hydrogen, carbon, and oxygen.
- Classification: C (Compound).

23. Thorium (Th):
- Pure thorium (one type of atom).
- Classification: E (Element).

24. Concrete:
- Mixture of cement, sand, gravel, and water.
- Classification: M (Mixture).

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Final Answer:

\[
\boxed{
\begin{array}{ll}
\text{1. Diamond (C)} & \text{E} \\
\text{2. Air} & \text{M} \\
\text{3. Krypton (Kr)} & \text{E} \\
\text{4. Sugar (C₁₂H₂₂O₁₁)} & \text{C} \\
\text{5. Sulfur (S)} & \text{E} \\
\text{6. Water (H₂O)} & \text{C} \\
\text{7. Alcohol (C₂H₅OH)} & \text{C} \\
\text{8. Ammonia (NH₃)} & \text{C} \\
\text{9. Salt (NaCl)} & \text{C} \\
\text{10. Wood} & \text{M} \\
\text{11. Seawater} & \text{M} \\
\text{12. Gasoline} & \text{M} \\
\text{13. Pile of Garbage} & \text{M} \\
\text{14. A dog} & \text{X} \\
\text{15. Energy} & \text{X} \\
\text{16. Iron (Fe)} & \text{E} \\
\text{17. Electricity} & \text{X} \\
\text{18. Uranium (U)} & \text{E} \\
\text{19. Popcorn} & \text{M} \\
\text{20. Gold (Au)} & \text{E} \\
\text{21. Pizza} & \text{M} \\
\text{22. Baking Soda (NaHCO₃)} & \text{C} \\
\text{23. Thorium (Th)} & \text{E} \\
\text{24. Concrete} & \text{M} \\
\end{array}
}
\]