7.a( change occurs when a material changes shape or size but the composition of the material does not change. 8. can be observed only when the substances in a sample of matter are changing into different substances. 9. materials can be classified as solids, liquids, or gases based whether their shapes definite or variable. 10. of matter states that all particles of matter are in constant motion.

7.A physical change occurs when a material changes shape or size but the composition of the material does not change.

8.Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.

9. Materials can be classified as solids, liquids, or gases based whether their shapes and volume are definite or variable.

10. The Kinetic theory of matter states that all particles of matter are in constant motion.

Explanation:

A change that causes no change in chemical composition of a substance is known as a physical change. This type of change can be easily measured or observed.

For example, mass, density, height, shape, size etc are all physical changes.

On the other hand, a change that leads to change in chemical composition of a substance is known as a chemical change. This change leads to formation of new substances.

For example, combustion, reactivity, toxicity etc are all chemical changes.

Kinetic theory of matter is defined as the theory which states that all particles of matter are in constant motion.

Thus, we can conclude that the given blanks are as follows.

A physical change occurs when a material changes shape or size but the composition of the material does not change.  Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.  Materials can be classified as solids,  liquids, or gases based whether their shapes and volume are definite or variable.  The Kinetic theory of matter states that all particles of matter are in constant motion.

He was the first to discover the electron and isotopes.