Chapter 2 Properties of Matter Section 2.1 Classifying Matter

Section 2.1 Classifying Matter Matter can be classified in 2 ways 1. 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).

Using properties to identify materials- 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.

Using properties to separate mixtures 2.2 Physical Properties Using properties to separate mixtures There are several separation techniques that can be used to separate mixtures. 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

Changes of states of matter are physical changes. 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).

4 Signs of a Chemical Change 1. Change in color. 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.

Chemical or Physical Change 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.