Unit 2: Elements, Compounds, Mixtures

Question 1

Element

Answer 1

one kind of atom

Examples: carbon, oxygen, nitrogen

Question 2

Compound

Answer 2

two or more elements bonded together

Examples: H2O (water), CO2 (carbon dioxide)

Question 3

mixture

Answer 3

two or more substances mixed together

Examples: salt water, cereal and milk

Question 4

pure substance

Answer 4

either a pure element or a pure compound

the opposite of a mixture

Question 5

homogenous mixture

Answer 5

a mixture which is the same all the way through, blended evenly.
Examples: hot cocoa, milk

Question 6

heterogeneous mixture

Answer 6

a mixture which is in chunks or layers

Examples: cereal and milk, oil and vinegar

Question 7

soluble

Answer 7

a substance which dissolves

Example: salt is soluble in water

Question 8

insoluble

Answer 8

a substance which does not dissolve

Example: sand is insoluble in water

Question 9

chemical change

Answer 9

a rearrangement of the atoms, breaking old bonds and making new bonds, to produce a new substance. Usually irreversable.
Example: burning paper produces ash

Question 10

physical change

Answer 10

a movement of a substance from one place to another or one form to another. Does not change the substance. Usually reversable.
Example: freezing water, melting ice

Question 11

filtration

Answer 11

removes an insoluble solid from a liquid
Can be used to separate a soluble solid and an insoluble solid.
Ex: tea in a tea bag

Question 12

Centrifuge

Answer 12

spins a mixture, causing the most dense particles to accumulate at the bottom of the test tube.
Uses density to separate a liquid mixture.
Ineffective with soluble solids.

Question 13

Chromatography

Answer 13

Uses affinity to water (or another liquid) to separate a mixture. The liquid moves up the chromatography paper and carries different substances different distances, thus separating them.

Question 14

Phase changes are always _______ changes.

Answer 14

Physical