Chemical Changes and Physical Properties

These flashcards cover key concepts related to chemical changes, physical properties, and the distinctions between pure substances and mixtures, as discussed in the lecture.

What is a pure substance?

A material made of only one type of particle. This includes elements (the simplest form of matter, like gold) and compounds (atoms joined together, like water), where every piece is the same.

What is a mixture?

A combination of two or more different substances that are not joined by chemical bonds. Because they are just mixed and not glued together, they can be separated by physical means like filtering.

Example: Sugar (C{6}H{12}O_{6})

Sugar is a pure substance because every small piece, called a molecule, is identical. A molecule is a group of two or more atoms stuck together acting as one unit.

What are physical properties?

Traits you can see or measure without turning the substance into something else. Examples include mass (how much matter is present), density (how tight those particles are packed), and color.

What is a chemical change?

A process where substances react to form entirely new molecules. Reactants (the starting ingredients) change into products (the new materials) with their own unique traits.

Explain the Law of Conservation of Mass.

This rule states that matter cannot be created or destroyed. In a reaction, the total weight or mass of the ingredients you start with must equal the total weight of what you end with.

What is chromatography?

A physical method used to separate a mixture by letting it travel across a surface. Different parts of the mixture move at different speeds because of how they stick to the surface, allowing them to be grouped separately.

What is a phase change?

When a substance moves between states—solid, liquid, or gas. This is a physical change because the identity of the molecules stays the same, even if they look different (like ice melting into water).

What is a physical change?

A change in the form or look of a substance (like melting, boiling, or crushing) without changing its chemical identity. The substance is still the same thing at its core.

How can mixtures be separated?

By using differences in physical traits. Common tools include filters for size, magnets for metal, or a centrifuge for density (separating items by how heavy or thick they are).

What is electrolysis?

A chemical process that uses electricity to tear a compound (like water, H_{2}O) apart into its basic elements (hydrogen and oxygen).

Physical vs. Chemical Properties

Physical properties describe a substance's current state (it is blue, it is heavy). Chemical properties describe how it could change (how it reacts with acid or if it is flammable).