Chapter 2 Properties of Matter

2.1 Properties of Matter  2.1 Classifying Matter

Pure Substances  Elements  Compounds

Elements  A substance that cannot be broken down into simpler substances.  Has a fixed composition because it contains only one type of atom.

Compounds  A substance that is made from two or more simpler substances and can be broken down into those simpler substances.  Always contains two or more elements joined in a fixed proportion.

Compounds

 Can be broken down into simpler substances.

Mixtures  The properties of a mixture can vary because the composition of a mixture is not fixed.

2 kinds of Mixtures  Heterogeneous  Homogeneous

Heterogeneous Mixture  The parts of the mixture are noticeable different from one another.

Homogeneous Mixture  The substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another.

Air is an homogenous mixture

Solutions, Suspensions, and Colloids  This is another way of classifying mixtures.  Based on the size of its largest particles.

Solution  When substances dissolve and form a homogeneous mixture.

Solutions  The particles in a solution are too small to settle out of the solution, be trapped by a filter, or scatter light.

Suspensions  A heterogeneous mixture that separates into layers over time

Suspensions  Over time, the suspended particles will settle to the bottom of the container.

Colloids  Contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension

2.2 Physical Properties  Any characteristic of a material that can be observed or measured with out changing the composition of the substances in the material.

Viscosity  The tendency of a liquid to keep from flowing, its resistance to flowing.  The greater the viscosity, the slower the liquid moves.

Conductivity  A material’s ability to allow heat to flow.  Metals have a high conductivity.

Malleability  The ability of a solid to be hammered without shattering.  Most metals are malleable.

Hardness  The resistance of a material to scratching.

Melting and Boiling Point  Melting: the temperature at which a substance changes from solid to liquid.  Boiling: the temperature at which a substance changes from a liquid to a gas.

Melting and Boiling Point

Density  The ratio of the mass of a substance to its volume.

Mass: the amount of stuff something is made up of.

Volume  How much space an object takes up.

Water displacement

Reading a Graduated Cylinder

Density tells you how tightly packed or loosely packed something is

Density also tells you if the particles in the substance are more like shot puts or ping pong balls

A bag or rocks is denser then a bag of styrofoam peanuts

When sacking groceries, where should the least dense items go?

What weighs more? A pound of feathers or a pound of lead?

Density Range  Hydrogen gas: g/cm 3 Osmium: 22 g/cm 3

Density of the Universe  5 × g/cm 3 or g/cm 3

Gold is dense: 19.3 g/cm 3  1 metric ton of gold = 1000 kg = 2200 lbs

Density Units = g/cm 3 or g/ml  Density tells you what the mass of the stuff would be if you had a cubic centimeter of the stuff.

Density determines if something sinks or floats

Why is it easier to float in salt water?

Density of Air

Density of the Earth

Population Density

Bone Density

10g 2 cm 3 10g/2cm 3 10g 2cm 3 Show work? Label every Number! = 5 g cm 3

Baggie #3

Baggie #2

Physical Properties  Physical properties are used to identify a material, to choose a material for a specific purpose or to separate the substances in a mixture.

Filtration

Chromatography

Distillation

Recognizing Physical Changes  A physical change occurs when some of the properties of a material change, but the substances in the material remain the same.

A phase change is a physical change.

2.3 Chemical Properties  Is any ability to produce a change in the composition of matter.  Chemical properties can be observed only when the substances in a sample of matter are changing into different substances.

Examples of Chemical Properties  Flammability is a material’s ability to burn in the presence of oxygen.

Examples of Chemical Properties  Reactivity is the property that describes how readily a substance combines chemically with other substances.

Recognizing Chemical Changes