Chapter 2 Properties of Matter

1. Chapter 2 Properties of Matter Section 2.1 Classifying Matter

2. 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

3. 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

4. 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).

5. 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)

6. 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.

7. 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.

8. 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).

9. 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.

10. 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.

11. 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

12. 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

13. 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.

14. 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).

15. 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.

16. 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.