chem quiz number 2

What is a physical change?

A change that affects the form of a substance but not its identity (e.g., phase change).

What is a chemical change?

A change that creates a new substance by rearranging atoms and molecules (e.g., rusting, burning, cooking).

What is density?

The amount of mass per volume of a substance (formula: D = m/v).

What is conductivity?

A measure of how well a material allows electricity or heat to flow.

What is malleability?

The ability of a substance to be hammered or rolled into sheets.

What is solubility?

How much of a substance (solute) can dissolve in a given amount of solvent.

What is a phase change?

A physical change from one state of matter to another (e.g., melting, boiling).

What is an extensive property?

A property that depends on the amount of substance present (e.g., mass, volume).

What is an intensive property?

A property that does not depend on the amount of substance present (e.g., density, color).

What is filtration?

A process that uses a barrier to separate solids from liquids.

What is distillation?

A process that separates homogeneous mixtures by using differences in boiling points.

What is sublimation?

When a solid changes directly into a vapor without passing through the liquid phase.

What is chromatography?

A technique that separates mixtures by moving them through a medium where components travel at different rates.

What is crystallization?

A process that results in the formation of solid crystals of a substance from a solution when the solution is supersaturated.

What are metals?

Good conductors, malleable, ductile, and solid at room temperature (except mercury).

What are nonmetals?

Poor conductors, brittle, often gases at room temperature.

What are metalloids?

Elements with properties of both metals and nonmetals; semiconductors.

Are nonzero digits significant?

Yes, all nonzero digits are always significant.

Are zeros between nonzero digits significant?

Yes, they are always significant.

Are leading zeros significant?

No, leading zeros are never significant.

Are trailing zeros significant?

Only if there is a decimal point present.

How many sig figs does 0.00450 have?

3 sig figs (4, 5, and the trailing zero).

How many sig figs does 2500 have?

2 sig figs (unless a decimal is added: 2500. → 4 sig figs).

Rule for multiplication/division with sig figs?

Answer should have the same number of sig figs as the number with the least sig figs in the problem.

Rule for addition/subtraction with sig figs?

Answer should have the same number of decimal places as the number with the least decimal places.