What is a homogeneous mixture? Which of the following are pure substances? Which of the following are homogeneous mixtures? Explain your answers. (a) Salt dissolved in water; (b) tea and ice; (c) chicken noodle soup; (d) mud; (e) gasoline; (f) carbon dioxide; (g) mint chocolate-chip ice cream.
The correct answer and explanation is:
Definition of a Homogeneous Mixture:
A homogeneous mixture is a combination of two or more substances that are uniform in composition and appearance throughout. In these mixtures, you cannot see the individual components, and the composition is the same no matter where you sample it. Common examples include air, saltwater, and vinegar.
Classification of Each Substance:
(a) Salt dissolved in water – Homogeneous mixture
Explanation: When salt dissolves in water, it forms a uniform solution. You cannot see the salt crystals, and every part of the solution tastes the same. This is a textbook example of a homogeneous mixture.
(b) Tea and ice – Heterogeneous mixture
Explanation: Tea is homogeneous, but once you add ice (solid water) to it, there are distinct phases (liquid and solid). The composition varies (tea in the liquid part, ice in the solid part), making it heterogeneous.
(c) Chicken noodle soup – Heterogeneous mixture
Explanation: You can see and separate the ingredients like chicken pieces, noodles, and broth. These components are not uniformly distributed, so it is not homogeneous.
(d) Mud – Heterogeneous mixture
Explanation: Mud consists of water mixed with soil or clay. It’s not uniform throughout, and particles settle over time. This makes it a heterogeneous mixture.
(e) Gasoline – Homogeneous mixture
Explanation: Gasoline is a carefully blended mixture of hydrocarbons. It appears uniform and consistent, so it qualifies as a homogeneous mixture.
(f) Carbon dioxide – Pure substance
Explanation: CO₂ is a compound made of carbon and oxygen in a fixed ratio. It cannot be separated into components by physical means and is therefore a pure substance.
(g) Mint chocolate-chip ice cream – Heterogeneous mixture
Explanation: You can see and taste different parts like chocolate chips and ice cream. The composition is not uniform, so it’s heterogeneous.
Summary:
Homogeneous mixtures: (a) Salt dissolved in water, (e) Gasoline
Pure substances: (f) Carbon dioxide
Not homogeneous (heterogeneous): (b) Tea and ice, (c) Chicken noodle soup, (d) Mud, (g) Mint chocolate-chip ice cream