A) Define atom, element, compound, and molecule. b) Explain the relationship between atom, element, and molecule using an example.

Here are the solutions to your questions.

Question 1:

a) Define the following terms as used in science:

• i) Atom: The atom is the smallest unit of an element that retains the chemical identity of that element. It consists of a nucleus (protons and neutrons) surrounded by electrons.
• ii) Element: An element is a pure substance consisting only of atoms that all have the same number of protons in their atomic nuclei. It cannot be broken down into simpler substances by chemical means.
• iii) Compound: A compound is a substance formed when two or more different chemical elements are chemically bonded together in a fixed ratio. Water ($\text{H}_2\text{O}$) is an example of a compound.
• iv) Molecule: A molecule is a group of two or more atoms held together by chemical bonds. These atoms can be of the same element (e.g., $\text{O}_2$) or different elements (e.g., $\text{CO}_2$).

b) Explain the relationship between atom, element, molecule using an example.
An atom is the fundamental building block of matter. An element is a pure substance made up of only one type of atom. For example, all atoms in a sample of pure oxygen are oxygen atoms, making oxygen an element. When two or more atoms chemically bond, they form a molecule. If two oxygen atoms bond, they form an oxygen molecule ($\text{O}_2$), which is still considered an element. If two hydrogen atoms bond with one oxygen atom, they form a water molecule ($\text{H}_2\text{O}$), which is a compound.

Question 2:
Write down the names of the following common elements:

• 1. Fe: Iron
• 2. Au: Gold
• 3. Na: Sodium
• 4. O: Oxygen
• 5. Cl: Chlorine
• 6. K: Potassium

Question 3:
Write a word equation for the formation of water.

$$\text{Hydrogen} + \text{Oxygen} \rightarrow \text{Water}$$

Question 4:
State the application of gold, aluminium and oxygen in the society.

• Gold: Used in jewelry, currency, and electronics due to its conductivity and resistance to corrosion.
• Aluminium: Used in aircraft construction, beverage cans, and window frames because it is lightweight, strong, and corrosion-resistant.
• Oxygen: Essential for respiration in living organisms, used in combustion processes, and for medical support in hospitals.

Question 5:
Explain 5 reasons for labelling substances in the society.

1. Safety Information: Labels provide crucial warnings about potential hazards (e.g., flammable, corrosive, toxic) to prevent accidents and ensure safe handling.
2. Ingredient Disclosure: They list the components of a substance, which is vital for consumers with allergies, dietary restrictions, or those needing to understand product composition.
3. Usage Instructions: Labels guide users on how to properly use, store, or dispose of a product, ensuring effectiveness and preventing misuse.
4. Identification and Branding: Labels help identify the product, its manufacturer, and brand, distinguishing it from similar items and building consumer trust.
5. Legal and Regulatory Compliance: Many substances require specific labeling by law to meet health, safety, and environmental regulations, ensuring accountability and consumer protection.