Properties and Changes of Matter

Identify matter, classify pure substances and mixtures, and distinguish physical from chemical changes.

Lesson 1 of 33 parts Practice Flashcards

1/3

Matter and Its Properties

Objective: Classify matter and identify physical properties.

Matter has mass and occupies space. A physical property, such as density, melting point, or electrical conductivity, can be observed without changing a substance’s chemical identity. An intensive property does not depend on sample amount, whereas an extensive property does. A property may help identify a substance, but one measurement alone is rarely conclusive.

Worked examples

Try itTwo samples of the same metal have masses 10 g and 20 g. Which listed property should remain the same?Show answer

1. Choose an intensive property: density. 2. Mass changes when the sample doubles. 3. For the same material under the same conditions, density remains the same.

Swipe sideways to move between sections

Matter and Its Properties

Objective: Classify matter and identify physical properties.

Worked examples

Try itTwo samples of the same metal have masses 10 g and 20 g. Which listed property should remain the same?Show answer

1. Choose an intensive property: density. 2. Mass changes when the sample doubles. 3. For the same material under the same conditions, density remains the same.

Elements, Compounds, and Mixtures

Objective: Distinguish elements, compounds, and mixtures.

An element consists of one type of atom; a compound contains different elements chemically combined in a fixed ratio. A mixture contains substances physically combined in variable proportions. Homogeneous mixtures are uniform at the sampling scale; heterogeneous mixtures are not. Filtration or distillation can separate mixture components, whereas breaking a compound into elements requires chemical change.

Worked examples

Try itIs saltwater a compound or a mixture?Show answer

1. Salt and water are separate substances. 2. Their proportions can vary. 3. Saltwater is a homogeneous mixture, not a new compound.

Physical and Chemical Changes

Objective: Use evidence to distinguish physical and chemical changes.

A physical change alters form or state without changing chemical composition; melting and dissolving are examples when the original species remain identifiable. A chemical change produces substances with different compositions, such as oxidation. Color change, gas release, or temperature change may be clues, but each requires context; a boiling liquid also releases gas without necessarily reacting. Conservation of atoms applies during chemical reactions.

Worked examples

Try itIce melts and then liquid water freezes. Did its chemical identity change?Show answer

1. Identify the material before and after: H₂O. 2. Only the state changed. 3. This is a physical change.

You finished the reading!

Lock it in with a few practice questions, then move on to the next lesson.

Practice Next lesson

Next lessonUnits and Significant Figures