CHAPTER 2 PROPERTIES OF MATTERSection 2.1 Classifying Matter

Section 2.1 Classifying Matter

Matter can be classified in 2 ways1. Pure Substance- Matter that always has exactly the same composition.• Fixed, uniform composition.

2 Types of Pure Substances• Elements- simplest substance of matter.

• Cannot be broken down into simpler substance• Atoms- smallest particle of an element.• Examples: H, Cl, Au

Section 2.1 Classifying Matter

Compounds- a substance made from two or more simpler substances and can be broken down into those simpler substances (elements or other compounds).• Always contains 2 or more elements joined in a fixed proportion.

• Examples: H2O, CO2

Section 2.1 Classifying Matter

2. Mixtures- properties can vary because the composition is not fixed.• Can retain some of the properties of their individual substances.

• Less constant than the properties of a substance.

2 Types of Mixtures

Heterogeneous mixture- a mixture in which the parts of the mixture are noticeably different from one another (not uniform).

Section 2.1 Classifying Matter

• Examples: Sand (grains of sand vary in size and color)

• Soil (soil is a mix of different elements, rocks and sediment)

Homogeneous mixtures- a mixture where the substances are so evenly distributed that it is hard to tell one substance from another (looks uniform).• Solutions are homogeneous mixtures• Examples: salt water, Windex,• Stainless steel (mix of Fe, Cr and Ni)

Section 2.1 Classifying Matter

Based on the size of its largest particles, a mixture can be classified as a solution, suspension, or a colloid.

1. Solution- when a substance dissolves and forms a homogenous mixture.• particles are too small to settle out, be trapped by a filter or scatter light (salt water).

2. Suspension- is a heterogeneous mixture that separates into layers over time.• Larger particles scatter light and therefore, suspensions are usually cloudy.

Ex: sand and water, orange juice and pulp.

Section 2.1 Classifying Matter

3. Colloid- contains some particles that are intermediate in size between small particles in a solution and the large particles in a colloid.• Like solutions they do not separate into layers and cannot use a filter to separate the particles.

• Like a suspension it can scatter light.• Ex: milk (fat dispersed and doesn’t separate into cream) or Fog.

2.2 Physical Properties

• Physical Property- is any characteristic of a material that can be observed or measured without changing the composition of the substances in the material.

• Examples: hardness, conductivity, boiling point, melting point, viscosity, malleability and density (these are vocabulary terms I would expect you to know).

2.2 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.

• Using properties to identify materials-• First you have to figure out what properties to test.

• Secondly, is to perform tests on the samples.• Thirdly, you need to compare your results to those of known materials.

• This is often used to help solve a crime.

2.2 Physical Properties

• Knowing about the properties of materials can help one figure out what type of material to use in certain items.

• Ex: If you are building a bridge a metallurgist would help the steel manufacturer to come up with the strongest type of metal to be used.

2.2 Physical Properties

• Using properties to separate mixtures• There are several separation techniques that can be used

to separate mixtures.

1. Filtration- is the process that separates materials based on the size of their particles.

Strainers or filter paper and funnels can be used to filter items.

Ex: Sand from water, rocks and sand

2. Distillation- is a process that separates the substances in a solution based on their boiling points.

Ex: Vinegar and water

3. Evaporation- is the process used to heat the water or any liquid to its vapor state. Ex: water from salt

2.2 Physical Properties

4. Magnetism-used to separate magnetic components of a mixture.

Ex: iron from sulfur

5. Chromatography- use to separate components of a solution by separating pigments using a solvent.

Ex: pigments in ink

6. Decant- to pour the liquids off and leave the solids behind. The solid must be on the bottom.

Ex: water from sediment

2.2 Physical Properties

• Physical change- a change that occurs when some properties of a material change, but the substance does not change.• Only physical properties change.• Some physical changes can be reversed- freeze and

melt water• Some physical changes cannot be reversed- peeling an

orange

• Changes of states of matter are physical changes.• Going from a gas to a liquid, or liquid to a solid and vice versa.

2.3 Chemical Properties

• Chemical property- 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.

• Ex: Flammability- a material’s ability to burn in the presence of oxygen (gasoline)

• Ex: Reactivity- a property that describes how readily a substance combine chemically with other substances (iron in air forms rust).

2.3 Chemical Properties

• Chemical Change-is when a substance reacts and forms one or more new substances.

• 4 Signs of a Chemical Change• 1. Change in color.• 2. Production of a gas.• 3. Heat or light are given off.• 4. A precipitate forms.

2.3 Chemical Properties

• Chemical or Physical Change• When matter undergoes a chemical change, the composition of the matter changes.

• When matter undergoes a physical change, the composition of the matter remains the same.