Problem 101 - Chemistry Matter and Change

Question

Identify each of the following as an element, a compound, a homogeneous mixture, or a heterogeneous mixture. (Chapter 3\()\) $$ \begin{array}{ll}{\text { a. air }} & {\text { d. ammonia }} \\ {\text { b. blood }} & {\text { e. mustard }} \\ {\text { c. antimony }} & {\text { f. water }}\end{array} $$

Step-by-Step Solution

Answer

Air is a homogeneous mixture, blood is a heterogeneous mixture, antimony is an element, ammonia and water are compounds, mustard is a heterogeneous mixture.

Step 1: Classify 'air'

Air is a mixture of different gases such as nitrogen, oxygen, carbon dioxide, and others. It is uniformly distributed, making it a homogeneous mixture.

Step 2: Classify 'blood'

Blood is composed of different components like red blood cells, white blood cells, plasma, and platelets, which exist in suspension. These components are visible under a microscope, classifying blood as a heterogeneous mixture.

Step 3: Classify 'antimony'

Antimony is a chemical element, symbolized by Sb, found on the periodic table. It is a pure substance and therefore classified as an element.

Step 4: Classify 'ammonia'

Ammonia is a chemical compound, consisting of nitrogen and hydrogen with the chemical formula NH₃. It is a pure substance composed of same molecules, classifying it as a compound.

Step 5: Classify 'mustard'

Mustard, a condiment made from seeds, water, and other ingredients, has visible seeds and varies in its consistency, making it a non-uniform mixture. Thus, it is classified as a heterogeneous mixture.

Step 6: Classify 'water'

Water is a chemical compound made of hydrogen and oxygen (11¶62). It has consistent properties throughout, classifying it as a compound.

Key Concepts

Elements

Elements are pure substances consisting entirely of one type of atom. Every element has its own unique properties and is represented by a chemical symbol on the periodic table. For instance, antimony is an element with the symbol Sb. It is a metalloid found naturally in the earth's crust. All atoms within an element share the same atomic number, meaning the same number of protons in their nucleus. When you encounter a substance that cannot be broken down further into simpler substances through chemical reactions, you are likely dealing with an element.

Compounds

Compounds are chemical substances formed from two or more elements combined in a fixed ratio. They have unique properties and can only be separated into simpler substances by chemical means. Water is a classic example, composed of hydrogen and oxygen in a 2:1 ratio, represented by the chemical formula \(H_2O\). Another example is ammonia, consisting of nitrogen and hydrogen with the formula \(NH_3\). Compounds have consistent properties throughout, quite distinct from the individual elements that compose them. This consistent characteristic allows them to be classified as substances of uniform composition.

Homogeneous Mixtures

Also known as solutions, homogeneous mixtures are composed of two or more substances, but these mixtures appear uniform. The different components are not visibly distinct, and the mixture has a consistent composition throughout. Air is a great example of a homogeneous mixture. It mainly consists of gases like nitrogen and oxygen, evenly distributed. The uniformity of homogeneous mixtures can often make it challenging to separate the individual components, and they typically require chemical methods for separation.

Heterogeneous Mixtures

Unlike homogeneous mixtures, heterogeneous mixtures have visibly different components that are not uniformly distributed. They are composed of two or more phases that can be observed individually. A common example is blood, which, when viewed under a microscope, reveals visible particles such as red and white blood cells and plasma. Similarly, mustard is a heterogeneous mixture where different components like seeds and liquids are visibly separate. These mixtures can be separated manually or through mechanical means, as opposed to requiring a chemical process like compounds or homogenous mixtures.