Chem- Chapter 3

3 examples of heterogeneous mixtures

1. Cereal in milk 2. Oil and water 3. Orange juice with pulp

What are the two properties of matter?

1. Has mass 2. Takes up space

3 examples of homogeneous mixtures

1. Sea water 2. Vinegar 3. Air

If the combination of iron filings and sulfur are heated strongly, the iron reacts with the sulfur to form a solid that is no longer attracted by the magnet. Would this still represent a mixture?

No, heating causes a reaction

The composition of a given pure compound is always ? no matter what the source of the compound

the same

Mixtures can be classified as either homogeneous or heterogeneous. Compounds cannot be classified in this way. Why not?

?

Sublimation definition and is it a physical or chemical change?

A change directly from the solid to the gaseous state without becoming liquid and it is a physical change

Filtration definition and example

A method for separating an insoluble solid from a liquid. Example- While preparing tea, a filter or a sieve is used to separate tea leaves from the water.

Heterogenous mixture

A mixture with uneven distribution of different substances, solids, liquids, gases.

Element

A pure substance made of only one kind of atom

Pure substance

A sample of matter, either a single element or a single compound, that has definite chemical and physical properties

Sieving definition and example

A simple method of separating particles of varying sizes. Example- Rice powder can be separated from soil using a sieve.

Crystallization definition and example

A solid phase is separated from a solution. Example- Copper sulphate crystallises with 5 molecules of water.

Compound

A substance made up of atoms of two or more different elements joined by chemical bonds

Chromatography definiton and example

A technique used to separate the components of a chemical mixture by moving the mixture along a stationary material, such as gelatin. Example- Paper chromatography

Why would a chemist find fault with the phrase "pure orange juice"?

Because it is a heterogeneous mixture (Bcs. of pulp), with water, vitamin c, pulp, sugar, etc.

Certain elements have special affinities for other elements. This causes them to bind together to form ?

Bonds

? can be broken down into the component elements by chemical changes

Compounds

Of the three states of matter, which are the least compressible?

Gas and liquid

In a sample of a gaseous substance, more than 99% of the overall volume of the sample is empty space. How is this fact reflected in the properties of a gaseous substance, compared with the properties of a liquid or solid substance?

Gaseous substances are more easily compressed and have more empty space. Liquids and solids have less empty space because the molecules do not move around as freely.

Element example and compound example

H and NaCl

What is the chief factor that determines the physical state of a sample of matter?

Heat

If iron filings are placed with excess powdered sulfur in a beaker, the iron filings are still attracted by a magnet and could be separated from the sulfur with the magnet. Would this combination of iron and sulfur represent a mixture or a pure substance?

Mixture

Are all physical changes accompanied by chemical changes? Are all chemical changes accompanied by physical changes?

Physical changes are not accompanied by chemical changes, but chemical changes are accompanied by physical changes.

Elemental bromine is a dense, dark-red, pungent-smelling liquid. Are these characteristics of elemental bromine physical or chemical properties?

Physical properties

The boiling point of water is (Physical or Chemical)

Physical, because the gaseous water is chemically the same as liquid

Are separations of mixtures physical or chemical changes?

Physical, because you are not changing the chemical makeup.

Distillation definition and example

Purifying a liquid by a process of heating and cooling. Example- Fermenting alcohol

Evaporation definition and example

Separates components of a mixture with a dissolved solid in a liquid. Example- Evaporating water

Centrifugation definition and example

Separating molecules having different densities by spinning them in solution around an axis (in a centrifuge rotor) at high speed. Example- The extraction of fat from milk in order to produce skimmed milk.

Sedimentation definition and example

Separation of insoluble substances which are heavier than liquid. Example- In a mixture of sand and water, sand settles down at the bottom.

Atom

Smallest particle of an element

if a piece of hard white blackboard chalk is heated strongly in a flame, the mass of the piece of chalk will decrease, and eventually the chalk will crumble into a fine white dust. does this change suggest that the chalk is composed of an element or a compound?

The chalk is a compound

What is true about the composition of a compound, no matter where we find the compound?

The compound is the same

Magnetic separation definition and example

The process of separating components of mixtures by using a magnet to attract magnetic substances. Example- Removing iron bearing minerals from silica sand used in the production of glass

Consider three 10-g samples of water; one as ice, one as liquid, and one as vapor. How do the volumes of these three samples compare with one another? How is this difference in volume related to the physical state involved?

The solid would have the smallest volume because it is the most condensed. A liquid would have a volume larger than the solid, but less than the gas. The gas would occupy the largest volume as the molecules move more freely.

Is there a difference between a homogeneous mixture of hydrogen and oxygen in a 2:1 ratio and a sample of water vapor?

There is not a difference, the state is changing but not the composition.

Separating funnel definition and example

Used to separate immiscible liquids. Example- A mixture of water and kerosene can be separated by using a separating funnel.

When water boils, you can see bubbles rising to the surface of the water. Of what are these bubbles made?

Water Vapor

Homogenous mixture

a mixture in which the composition is uniform throughout

If you place a glass rod over a burning candle, the glass turns black. What is happening to each of the following (physical change, chemical change, both, or neither) as the candle burns? a. the wax b. the wick c. the glass rod

a. Physical b. Chemical C. Chemical and Physical