Lesson 2.1: Matter has observable properties

Lesson Focus

All matter has unique characteristics. This lesson introduces the scientific way of observing matter by exploring its physical and chemical properties and the changes it undergoes.

Learning Objectives

• Describe the difference between physical and chemical properties that define all matter.
• Give examples of physical changes, where a substance's identity does not change.
• Explain how chemical changes, such as burning, result in entirely new substances.
• Observe the tell-tale signs of a chemical change in a hands-on experiment.

We identify matter by observing its characteristics without changing what it is.

These physical properties, like color, texture, mass, and volume, can be seen or measured. A clay block's shape can change, but it's still clay.

Takeaway: Physical properties describe a substance's identity without altering it.

Some same-sized objects feel heavier than others because of density, a key physical property relating mass to space.

We calculate it with the formula D = m/V. This value is constant for a substance, no matter its size.

Takeaway: Density is a reliable property for identifying a substance.

When a substance's appearance changes but its chemical identity does not, it's a physical change. This alters properties like shape, size, or state of matter (ice melting to water). The molecules are the same, just arranged differently. Takeaway: A physical change alters form, not the fundamental substance.

A chemical property describes a substance’s ability to form something new, like wood's ability to burn.

This process is a chemical change, where atoms from original substances rearrange to create entirely new ones, like ash from wood.

Takeaway: Chemical changes produce new materials with different properties.

Since we can't see atoms rearranging, we look for clues that a chemical change happened.

Key signs include a change in odor or color, the formation of bubbles (a gas) or a solid (precipitate), and a change in temperature.

Takeaway: Observable signs help us identify chemical reactions.