Classify the following as either pure substances or mixtures. If it is a pure substance, state whether it is a compound or an element. If it is a mixture, state whether it is homogenous or heterogeneous.
a.) Aluminum foil
b.) Water
c.) Salt Water
d.) Oil + Water
e.) Table Salt
f.) Air
g.) Flour + Baking powder
h.) steel nails
I.) Iron Pipe
j.) Brass
k.) 200 proof alcohol
l.) 10 carat gold
The correct answer and explanation is :
Let’s classify each of the substances listed as either a pure substance or a mixture, and if it’s a mixture, determine whether it is homogeneous or heterogeneous:
a.) Aluminum foil
- Classification: Pure substance (Element)
- Explanation: Aluminum foil is made of a single element, aluminum (Al), in a pure form. It doesn’t contain any other substances mixed with it.
b.) Water
- Classification: Pure substance (Compound)
- Explanation: Water (H₂O) is a chemical compound, composed of hydrogen and oxygen in a fixed ratio. It has consistent properties throughout.
c.) Salt Water
- Classification: Mixture (Homogeneous)
- Explanation: Salt water is a mixture of salt (NaCl) dissolved in water. The salt is uniformly distributed in the water, making it a homogeneous mixture.
d.) Oil + Water
- Classification: Mixture (Heterogeneous)
- Explanation: Oil and water do not mix uniformly. Since oil is less dense and does not dissolve in water, the mixture has separate layers, making it heterogeneous.
e.) Table Salt
- Classification: Pure substance (Compound)
- Explanation: Table salt is sodium chloride (NaCl), a compound formed from sodium and chlorine in a specific ratio. It is a pure substance with consistent properties.
f.) Air
- Classification: Mixture (Homogeneous)
- Explanation: Air is a mixture of gases like nitrogen, oxygen, carbon dioxide, and other trace gases. The gases are uniformly distributed, making air a homogeneous mixture.
g.) Flour + Baking Powder
- Classification: Mixture (Heterogeneous)
- Explanation: Flour and baking powder are mixed together but do not form a uniform composition. The particles are separate and visible, making this a heterogeneous mixture.
h.) Steel nails
- Classification: Mixture (Homogeneous)
- Explanation: Steel is an alloy made of iron and carbon (along with other elements). The alloy is uniform in composition, so steel nails are a homogeneous mixture of these elements.
i.) Iron Pipe
- Classification: Pure substance (Element)
- Explanation: An iron pipe is made primarily of iron (Fe), which is a single element. It is a pure substance.
j.) Brass
- Classification: Mixture (Homogeneous)
- Explanation: Brass is an alloy made of copper and zinc. It has uniform properties throughout the material, so it is a homogeneous mixture.
k.) 200 proof alcohol
- Classification: Pure substance (Compound)
- Explanation: 200 proof alcohol is pure ethanol (C₂H₅OH) with no water content. It is a single chemical compound.
l.) 10 carat gold
- Classification: Mixture (Homogeneous)
- Explanation: 10-carat gold is an alloy made of gold and other metals, typically copper or silver. Since it is mixed uniformly, it is a homogeneous mixture.
Summary:
- Pure substances (Elements/Compounds): Aluminum foil, Water, Table Salt, Iron Pipe, 200 proof alcohol
- Mixtures (Homogeneous): Salt water, Air, Steel nails, Brass, 10 carat gold
- Mixtures (Heterogeneous): Oil + Water, Flour + Baking powder
This classification is based on the nature of the components: pure substances consist of a single type of material, while mixtures contain more than one component. Homogeneous mixtures have a uniform composition, whereas heterogeneous mixtures have distinguishable components.