Elements and Compounds

These Worksheets are for Grade 7 students to help them review the topic ‘Elements and Compounds’. It will help them achieve more knowledge about the substances that play an important role in our lives. Such questions, as in this practice sheet, will not only help students assess themselves but will also help tutors to know the level of understanding in students. The worksheets consists of multiple choice questions, give-one-word-answer and match-the-following which makes it more interesting to solve. These worksheets, and many more have been created by expert grade 7 science tutors who understand the importance of practice and questioning in the education of STEM subjects.

Elements

Everything around us is made up of elements. Let’s take the air we breathe is mixture so many elements like oxygen, nitrogen, and argon. They are the constituting factors for everything on this planet Earth: the tree, your book, your pencil, paper, and furniture, so on.

An element is a pure substance that cannot be broken down by chemical methods into simpler parts.

There are a total of 118 elements.

Many elements occur naturally on Earth; however, some are created in a laboratory by scientists by nuclear processes.

Compounds

Every combination of atoms is a molecule. Numerous atoms of different elements combine to form a compound molecule. All compounds are molecules but all molecules are not compounds. Molecule is one that is formed together out of a chemical bond.

Credit: https://chemistry.stackexchange.com/questions/2879/what-is-the-definition-of-of-compound-mixture-element-and-molecule

What elements and compounds have in common?

Both, elements and compound are pure chemical substances.

Physical changes: A change which does not affect the substance. Physical forces cannot always break down compounds totally. Heat melts ice to form water. But no change happens to the molecule of water. Like -wise decreasing the pressure boils water leaving the molecules unchanged.

The process of curdling of milk is also an example of chemical change.

1. A new substance is formed
2. The process is irreversible

There are millions of different compounds around us. When elements join and become compounds, they lose many of their individual behavior. Sodium (Na) is very reactive element individually but when sodium and chlorine (Cl) combine, table salt forms which is a non-reactive and obviously very edible substance. New compounds formed rarely posses any of their previous physical or chemical traits when they were elements. They have a new life of their own.

Check Point

A. Fill in the blanks:

1. An …………… Is a pure substance that cannot be broken down by chemical methods into simpler components.
2. An …………… is the smallest particle of an element that still has the same properties of that element.
3. There are a total of …………… elements.
4. A …………… is a molecule made of atoms from different elements.
5. …………… …………… in compounds happen when chemical bonds are created or destroyed.

Sample Questions

Q1. One Word Answer: 

1.  It takes the shape of the container._____________
2. It is made up of particles/atoms of only one kind._____________
3. A Compound is same throughout in properties and composition. We call it _________________
4. A Smallest unit of an element that has all the basic properties of the element._________________
5. It is made up of two or more kinds of atoms or compounds mixed in any proportion.________________
6. This molecule is made of two atoms of hydrogen and one atom of oxygen._______________
7. One example of an element. ________________
8. The elements are placed in specific locations because of the way they look and act. _________________
9. These substances will have a constant appearance, color and density throughout the sample. ________________
10. Objects that take up space and have mass._________________

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