Which of the following statements is incorrect?

Options

A. When compounds are formed, heat is often given off.
B. Unlike elements, compounds and mixtures are both impure substances.
C. Unlike compounds, mixtures can be separated into its components by physical means.
D. Compounds and mixtures are both made of elements

Answer

To determine which statement is incorrect, let's analyze each statement one by one.

### Step 1: Analyze the First Statement
**Statement:** When compounds are formed, heat is often given off.

**Analysis:** This statement is generally true. Many chemical reactions that form compounds are exothermic, meaning they release heat. Therefore, this statement is correct.

### Step 2: Analyze the Second Statement
**Statement:** Unlike elements, compounds and mixtures are both impure substances.

**Analysis:** This statement is incorrect. Elements are pure substances because they consist of only one type of atom. Compounds are also pure substances because they have a fixed composition of different types of atoms bonded together. Mixtures, on the other hand, are combinations of two or more substances that can vary in composition and are considered impure. Thus, this statement is false.

### Step 3: Analyze the Third Statement
**Statement:** Unlike compounds, mixtures can be separated into components by physical means.

**Analysis:** This statement is true. Mixtures can be separated by physical methods such as filtration, distillation, or centrifugation, while compounds require chemical reactions to separate their constituent elements. Therefore, this statement is correct.

### Step 4: Analyze the Fourth Statement
**Statement:** Compounds and mixtures are both made of elements.

**Analysis:** This statement is true. Compounds are made of two or more different elements chemically bonded together, while mixtures can contain two or more elements or compounds that are not chemically bonded. Thus, this statement is correct.

### Conclusion
After analyzing all the statements, the incorrect statement is the second one: "Unlike elements, compounds and mixtures are both impure substances."

### Final Answer
The incorrect statement is: **"Unlike elements, compounds and mixtures are both impure substances."**

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