Unit 2. Matter

Page 1

1. Properties of matter

Matter is anything that has mass and volume. To describe a physical system we need to know its properties.

General properties: that don´t give information to know what kind of material we are studying.

Specific properties: properties that give information to differenciate the matter.

2. General properties

Mass: this physical quantity is related with the amount of matter that a physical system has.

Vulume this physical quantity is related with the copied space of a physical system.

3. Specific properties

Density: this physical quantity relates the mass of an object and its volume. Density equals volume per mass.

4. Pure substances and mixtures

A pure substance is a type of matter that can´t descomposed by physical methods.

Simple: H2, O2

Composed: H2O, CO2

A mixture is formed by pure substances that can be separated by physical methods.

Heterogeneous mixture: the substance can be distinguished at first glande.

Homogeneous mixture (solutions): at first glande we can´t see the different between a pure substance and a solution.

Page 2

5. Solutions

Solvent: the substances that the bigger proportion in the solution.

Solute: the substance that is dissolved in the solution. We can find various solutes in a solution.

6. Concentration

Concentration equals mass of the solute per volume. The concentration of a solution is the amount of a solute in a certain amount of solution.

C: concentration (g/L)

Ms: mass of the solution (g)

V: volume of the substance (L)

7. Solubility

Is the concentration of the saturated solution. The value of this concentration depends of this concentration on the solute, the solvent and the temperature.

Diluted: if the concentration of a solution is much less than the solubility, the solution is dilued.

Concentrated: when it reaches solubility, the solution stops dissolving solute and the solute precipitates.

Saturated: when it reaches solubility, thee solution stops dissolving solute and the solute precipitates.

Oversaturated: it isn´t possible to dissolve more solute at the temperature and it that volume of solvent. The solute precipitates.

8. tchniques for separating mixtures

Decantation: separating of two substances that don´t mix (inmisible) usually two liquids. Separating water and oil by letting the mixture settle and then removing the water.

Filtration: a method used to separate an insoluble solid from a liquid, by passing the mixture from a filter that remains solid.

Centrifugation: a technique that speeds up the separation of a solid and a liquid or two liquids with defferent dnsity by spinning the mixture quickly. Cream from milk.

Distillation: sparation of mixture of liquids with different boiling points. Separating water and alcohol in a mixture.

Crystallization: a method used to separate a solid which is dissolved in a liquid by evaporating or cooling the solution.

9. Changes of state

Changes os state are physical transformations that occur when a substance passes fromone state of the matter to another: solid, liquid and gas.

Solid to liquid: melting

Liquid to gas: vaporization

Gas to liquid: condensation

Liquid to solid: solidification

Solid to gas: sublimation

Gas to solid: deposition