Compounds and Mixtures

The Periodic TableContains 118 known elements.It´s organised in rows (periods) and columns (groups).

periods

groups

The Periodic table arranged the atoms in an organised way. If you read across each row (period) from left to right, the atoms increase in mass.

The Periodic Table

Metals and Non metalsElements with similar properties are close together. Transition metal

Alkalimetal

Alkaline Earth

Formulae : Particle models

A molecule of:

A compound of:

H

H

H

HO OC H HO C

Carbon dioxide CO2

Water H2O

Methane CH4

Compounds

Chemical name Formula What the compund containsHow many elements

Calcium oxide CaO One calcium atom bonded to one oxygen atom 2 different elements

Carbon dioxide CO2 One carbon atom bonded to two oxygen atoms 2 different elements

Carbon monoxide CO One carbon atom bonded to one oxygen atom 2 diferent elements

Hydrogen sulfide H2S Two hydrogen atoms bonded to one sulfur atom 2 diferent elements

Calcium carbonate CaCO3one calcium atom, one carbon atom and three oxygen atoms bonded together

3 different elements

Identify the Elements and Compounds:

Na CaCl2

Pb(C2H3O2)2 C2H2Cl2O2

lead acetate II

Sodio

C2H2Cl2O2

dichloroacetic acid

W AsTungsten

Arsenic

Answer…. Go to the page

93 of your Coursebook and answer questions 1 to 4.

Unit 8 Mixtures Topic 8.1 Compounds and mixtures

1) Carbon dioxide, nitrogen, oxygen and water or steam. Accept the formulae CO2 , N2 , O2 and H2 O. 2) The gases in the air that are elements are nitrogen and oxygen. You can tell this because they are made of only one kind of particle (or atom). 3)The gases in the air that are compounds are carbon dioxide and water. You can tell this because they are made up of more than one type of particle (or atom) bonded together. For example, carbon dioxide is made up of carbon and oxygen atoms joined together.4) Air is a mixture and not a compound because it is made up of different elements and compounds that are mixed together but not joined or bonded together

Mixtures

Types of Mixtures

  Mixture Compound

CompositionVariable composition you can vary the amount of each substance in a mixture.

Definite composition you cannot vary the amount of each element in a compound.

Joined or notThe different substances are not chemically joined together.

The different elements are chemically joined together.

PropertiesEach substance in the mixture keeps its own properties.

The compound has properties different from the elements it contains.

SeparationEach substance is easily separated from the mixture.

It can only be separated into its elements using chemical reactions.

Examples Air, sea water, most rocks.Water, carbon dioxide, magnesium oxide, sodium chloride.

Is there a difference?

Look……

http://www.bbc.co.uk/bitesize/ks3/science/chemical_material_behaviour/compounds_mixtures/activity/

Use your Workbook

MIXTURES: Solve pg. 66, 67, 68, 69.

Making Mixtures

Contain different substances that are not combined together chemically.

Separating Mixtures

“Separating solids from liquids” - 1.FiltrationIf a substance does not dissolve in a solvent, we say

that it is insoluble. For example, sand does not dissolve in water – it is

insoluble.

Method for separating an insoluble solid from a liquid.

When a mixture of sand and water is filtered:

the sand stays behind in the filter paper (it becomes the residue)

the water passes through the filter paper (it becomes the filtrate)

The liquid particles are small enough to pass through the filter paper as a filtrate. The solid particles are too large to pass through the filter paper and stay behind as a residue.

“Separating solids from liquids” –

2.EvaporationEvaporation is used to separate a soluble solid from a

liquid.

For example, copper sulfate is soluble in water – its

crystals dissolve in water to form copper sulfate solution.

During evaporation, the water evaporates away leaving

solid copper sulfate crystals behind.

Separating Mixtures

A solution is placed in an evaporating basin and heated with a Bunsen burner.

The volume of the solution has decreased because some of the water has evaporated. Solid particles begin to form in the basin.

All the water has evaporated, leaving solid crystals behind

The volume of the solution has decreased because some of the water has evaporated. Solid particles begin to form in the basin.

All the water has evaporated, leaving solid crystals behind

Previous

.

Separating the solvent from a solution – simple distillation

Separating the solvent from a solution – 3. simple distillation

For example, water can be separated from salt

solution by simple distillation. This method works

because water has a much lower boiling point than

salt.

Salt solution is heated

All the water has evaporated from the salt solution, leaving the salt behind

Separating dissolved solids – 4.Chromatography

Method for separating dissolved substances from one another. It is often used when the dissolved substances are coloured, such as inks, food colourings and plant dyes

SolutionsAll solutions are

“transparent “

salt

Mass of solute + mass of solvent

mass of solution

Conservation of mass

Solubility

Temperature and Solubility

As the Temperature increases the solubility of most solutes increases.

Use your Wokbook

Solve pg. 54 & 55.

Exercise 6.2 Diffusion

1 ) Particles from the food pass into the air. These particles are free to move and they spread out into the air. This process is called diffusion. (Note that, in practice, much of the movement of the smell is likely to be caused by convection currents, but students will not yet have learnt about these.2 ) You might open a window or move the air about by waving your arm or by putting on a fan. This will cause the particles causing the smell to move about and spread to new areas, so that there are fewer of them in the air in the room. 3 a )They do not know how concentrated the sodium hydroxide is so they should wear safety glasses and avoid getting it on their skin. b) They can tell that the sodium hydroxide has diffused because as the particles move into the agar jelly the Universal Indicator will change colour because sodium hydroxide is an alkali. Credit mention of the change of Universal Indicator to green and/or blue. They can find out how far it has diffused by measuring the distance of the edge of the green or blue area from the circle, or by measuring the diameter of the green or blue area.

first attempt second attempt third attempt mean

A 3.2 2.9 3.5 3.2B 0.7 0.6 0.5 0.6

C 1.5 2.4 2.6

2.5NB the odd result, 1.5, should be

ignoredD 1.6 1.4 1.8 2.6

Distance diffused in 10 minutes / cm Sodium hydroxide

e) Bottle A. f In the time allowed, this sodium hydroxide has diffused the furthest. There are more particles present so there is more movement of particles in the 10 minutes allowed.

c,d

three pure substances. The sample on the left is a mixture of all three.