Class 7 (Science Assignment)

 

Elements and Compounds

Everything around us is made up of matter. Matter can be classified into different substances, including elements and compounds. An element is a pure substance made up of only one kind of atom. Examples of elements are oxygen, iron, gold, copper, and hydrogen. Each element has its own properties and cannot be broken down into simpler substances by ordinary chemical methods.

A compound is a pure substance formed when two or more different elements combine chemically in a fixed proportion. Water is a common example of a compound. It is made up of hydrogen and oxygen. Similarly, carbon dioxide is made up of carbon and oxygen. The properties of a compound are usually different from the properties of the elements that form it.

Elements are represented by symbols, such as O for oxygen, Fe for iron, and Au for gold. Compounds are represented by chemical formulae. For example, H₂O represents water, while CO₂ represents carbon dioxide. Understanding elements and compounds helps us understand the composition and behaviour of substances around us.

Questions

1.     What is an element? Give two examples.

2.     What is a compound?

3.     How are the properties of a compound different from those of its constituent elements?

4.     What elements are present in water?

5.     Write the chemical formulae of water and carbon dioxide.

6.     What is the difference between an element and a compound?