2.3 elements and compounds
52. how could you distinguish an element from a compound?
*53. classify the following materials as an element, compound, or mixture. give reasons for your answers.
a. table salt (nacl)
b. salt water
c. sodium (na)
54. describe the relationship between the three items in each of the following groups. identify each item as an element, compound, or mixture.
a. hydrogen, oxygen, and water
b. nitrogen, oxygen, and air
c. sodium, chlorine, and table salt
d. carbon, water, and table sugar

Question

2.3 elements and compounds
52. how could you distinguish an element from a compound?
*53. classify the following materials as an element, compound, or mixture. give reasons for your answers.
  a. table salt (nacl)
  b. salt water
  c. sodium (na)
54. describe the relationship between the three items in each of the following groups. identify each item as an element, compound, or mixture.
  a. hydrogen, oxygen, and water
  b. nitrogen, oxygen, and air
  c. sodium, chlorine, and table salt
  d. carbon, water, and table sugar

Accepted Answer

### Question 52
# Brief Explanations:
To distinguish an element from a compound, we can use the following criteria:
- **Element**: A pure substance made up of only one type of atom. It cannot be broken down into simpler substances by chemical means (e.g., gold, oxygen).
- **Compound**: A pure substance made up of two or more different elements chemically bonded in a fixed ratio. It can be broken down into its constituent elements by chemical reactions (e.g., water $ \ce{H_2O} $ can be split into hydrogen and oxygen via electrolysis).

A practical test is chemical decomposition: if a substance can be broken down into simpler substances with distinct properties (e.g., different elements), it is a compound; if not, it is an element.

# Answer:
An element is a pure substance with only one type of atom (cannot be chemically broken down into simpler substances). A compound is a pure substance with two or more elements chemically bonded (can be broken down into elements by chemical reactions).

### Question 53
#### Part (a): Table Salt ($ \ce{NaCl} $)
# Brief Explanations:
- **Classification**: Compound.
- **Reason**: Table salt ($ \ce{NaCl} $) is made of two different elements (sodium, $ \ce{Na} $, and chlorine, $ \ce{Cl} $) chemically bonded in a fixed 1:1 ratio. It is a pure substance with a definite composition and can be broken down into $ \ce{Na} $ and $ \ce{Cl} $ via chemical reactions (e.g., electrolysis of molten $ \ce{NaCl} $).

#### Part (b): Salt Water
# Brief Explanations:
- **Classification**: Mixture.
- **Reason**: Salt water contains two substances (sodium chloride, $ \ce{NaCl} $, and water, $ \ce{H_2O} $) physically mixed (not chemically bonded). The ratio of salt to water can vary, and the components retain their individual properties (e.g., salt can be separated by evaporation).

#### Part (c): Sodium ($ \ce{Na} $)
# Brief Explanations:
- **Classification**: Element.
- **Reason**: Sodium ($ \ce{Na} $) is a pure substance made up of only sodium atoms. It cannot be broken down into simpler substances by chemical means (e.g., it remains $ \ce{Na} $ in chemical reactions unless combined with other elements).

### Question 54
#### Part (a): Hydrogen, Oxygen, and Water
# Brief Explanations:
- **Hydrogen ($ \ce{H_2} $)**: Element (pure substance, only hydrogen atoms).
- **Oxygen ($ \ce{O_2} $)**: Element (pure substance, only oxygen atoms).
- **Water ($ \ce{H_2O} $)**: Compound (pure substance, hydrogen and oxygen atoms chemically bonded in a 2:1 ratio).
- **Relationship**: Hydrogen and oxygen are elements that chemically combine (via combustion or synthesis) to form the compound water. Water can be decomposed (e.g., electrolysis) back into hydrogen and oxygen.

#### Part (b): Nitrogen, Oxygen, and Air
# Brief Explanations:
- **Nitrogen ($ \ce{N_2} $)**: Element (pure substance, only nitrogen atoms).
- **Oxygen ($ \ce{O_2} $)**: Element (pure substance, only oxygen atoms).
- **Air**: Mixture (contains nitrogen, oxygen, carbon dioxide, etc., physically mixed in variable proportions).
- **Relationship**: Nitrogen and oxygen are elements that are major components of air (a mixture). Air is not a compound because its components are not chemically bonded and their ratios can vary.

#### Part (c): Sodium, Chlorine, and Table Salt
# Brief Explanations:
- **Sodium ($ \ce{Na} $)**: Element (pure substance, only sodium atoms).
- **Chlorine ($ \ce{Cl_2} $)**: Element (pure substance, only chlorine atoms).
- **Table Salt ($ \ce{NaCl} $)**: Compound (pure substance, sodium and chlorine atoms chemically bonded in a 1:1 ratio).
- **Relationship**: Sodium and chlorine are elements that chemically react (e.g., combustion) to form the compound table salt. Table salt can be decomposed (e.g., electrolysis) back into sodium and chlorine.

#### Part (d): Carbon, Water, and Table Sugar
# Brief Explanations:
- **Carbon ($ \ce{C} $)**: Element (pure substance, only carbon atoms).
- **Water ($ \ce{H_2O} $)**: Compound (pure substance, hydrogen and oxygen atoms bonded in a 2:1 ratio).
- **Table Sugar ($ \ce{C_{12}H_{22}O_{11}} $)**: Compound (pure substance, carbon, hydrogen, and oxygen atoms bonded in a fixed ratio).
- **Relationship**: Carbon is an element. Water and table sugar are compounds that both contain hydrogen and oxygen, but table sugar also contains carbon. Carbon can combine with hydrogen and oxygen (e.g., via photosynthesis in plants) to form sugar, while water is a simpler compound of hydrogen and oxygen.

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QUESTION IMAGE

Question

Explanation:

Question 52

Part (b): Salt Water

Part (c): Sodium (\( \ce{Na} \))

Answer:

Question 53

Part (a): Table Salt (\( \ce{NaCl} \))