A single substance that exists in two or more forms is called

Options

A. polymorphous
B. amorphous
C. isomorphous
D. monomorphous

Answer

To solve the question "A single substance that exists in two or more forms is called," we can follow these steps:

### Step 1: Understand the Concept
We need to identify the term that describes a single substance existing in different forms. This concept is fundamental in chemistry and relates to how substances can exhibit different physical properties depending on their structural arrangement.

### Step 2: Identify the Key Terms
From the video transcript, we note the terms "polymorphism" and "allotropy." Both terms refer to the phenomenon of a substance existing in multiple forms.

### Step 3: Differentiate Between the Terms
- **Polymorphism**: This term is used for substances that can exist in different forms or crystal structures. It applies to both organic and inorganic compounds.
- **Allotropy**: This term is specifically used for elements that can exist in different forms. For example, carbon can exist as graphite and diamond.

### Step 4: Conclusion
Since the question asks for a single substance that exists in two or more forms, the correct answer is **polymorphism**. If the substance in question is an element, then it would be referred to as allotropy.

### Final Answer
The term for a single substance that exists in two or more forms is **polymorphism**.

---