Question

in a science fair, isaac, lesha, and mykol are presenting their project on pure substances. lesha listed milk, oxygen, water, and carbon dioxide as examples in their presentation. which of these, according to isaac, is not a pure substance?

Explanation:

Step1: Recall the definition of pure substance

A pure substance has a uniform and definite composition.

Step2: Analyze each option

• Milk: It is a mixture of water, fats, proteins, etc.
• Sugar: It has a definite chemical formula \(C_{12}H_{22}O_{11}\) and is a pure substance.
• Salt: Usually refers to sodium chloride (\(NaCl\)) which is a pure substance.
• Air: It is a mixture of nitrogen, oxygen, carbon dioxide, etc.

Answer:

Milk and air.