Compounds and Mixtures

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

The Periodic Table 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.

Metals and Non metals Transition metal Elements with similar properties are close together. Transition metal Alkali metal Alkaline Earth

Formulae : Particle models A molecule of: A compound of:

Compounds H H O C O H O H C H H Carbon dioxide Water Methane CO2 H2O

Identify the Elements and Compounds: Na CaCl2 W As Sodio C2H2Cl2O2 Tungsten Arsenic Pb(C2H3O2)2 C2H2Cl2O2 dichloroacetic acid lead acetate II

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

Is there a difference? Composition   Mixture Compound Composition Variable 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 not The different substances are not chemically joined together. The different elements are chemically joined together. Properties Each substance in the mixture keeps its own properties. The compound has properties different from the elements it contains. Separation Each 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.

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.Filtration If 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 Mixtures “Separating solids from liquids” – 2.Evaporation Evaporation 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.

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 All the water has evaporated, leaving solid crystals behind

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

Solutions All solutions are “transparent “ Conservation of mass 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.

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