7H Solutions

1. 7H Solutions 7H Solutions Mixtures and solutions Separation techniques More about solutions

2. 7H Solutions Mixtures and solutions

3. 7H Mixtures and solutions - Is it pure or is it a mixture? A pure substance contains just one type of particle. A mixturecontains at least two different types of particle. A liquid can be pure or a mixture. Which of these liquids is a mixture?  It’s a trick question – they’re all mixtures! Do you know why?

4. 7H Mixtures and solutions - Does the solid dissolve? solid + liquid mixture Does the solid dissolve? YES NO solid – no longer visible liquid – may change colour   A solid that dissolves in water is soluble. solid – still visible liquid – no colour change A solid that does not dissolve in water is insoluble.

5. 7H Mixtures and solutions - What’s the solution? When a solid dissolves in a liquid it forms a special type of mixture called a solution. solute solution - formed when the solvent and solute mix together solute - the substance being dissolved (a solution can have more than one solute but only one solvent) solvent - the liquid/substance that does the dissolving solvent - the liquid/substance that does the dissolving solute solution and solvent solvent solvent Click on the beaker for some important solution words beginning with “s”!

6. 7H Solutions Separation techniques

7. 7H Separation techniques - Filtration Mixtures of liquids and solids can be separated by separation techniques. Insoluble solids can be separated from a liquid by filtering. How would you separate pasta from the cooking water? How are tea leaves kept out of a cup of tea? How are coffee grains separated from a pot of fresh coffee?

8. 7H Separation techniques - Worth your salt? Did you know that salt is a surprisingly super-talented solid? See if you’re “worth your salt” by deciding if the following statements are true or false. 4. Salt is found naturally dissolved in seawater. The total amount of salt dissolved in the world’s oceans would cover the area of Britain to a depth of 3 miles! 4. Salt is found naturally dissolved in seawater. The total amount of salt dissolved in the world’s oceans would cover the area of Britain to a depth of 3 miles! FALSE! All the salt in the oceans would cover Britain to a depth of 50 miles! 2. Salt is found in every cell of your body. An adult human body contains about 70 grams of salt. FALSE! Salt is found in every cell of your body but an adult human contains about 250 grams of salt! 3. Spilling salt was considered unlucky. If you spill salt some people say you should throw some over your right shoulder to cancel out the bad luck! 3. Spilling salt was considered unlucky. If you spill salt some people say you should throw some over your right shoulder to cancel out the bad luck! FALSE! Spilling salt is unlucky but you should throw the salt over your left shoulder. 1. Salt has been used as currency. The saying “being worth your salt” comes from ancient Greece, where slaves were traded in exchange for salt. TRUE! How much salt would you be worth? 2. Salt is found in every cell of your body. An adult human body contains about 70 grams of salt. 1. Salt has been used as currency. The saying “being worth your salt” comes from ancient Greece, where slaves were traded in exchange for salt.

9. 7H Separation techniques - Salty seawater You can think of the sea as a very big mixture. What kinds of solids are found in seawater? It’s easy to separate the insoluble solids like fish and boats. It’s more difficult to separate the soluble solids like salt. How could you separate the salt from a salty seawater solution?

10. 7H Separation techniques - Evaporation To separate dissolved solids from a solution, you need to remove the liquid. Removing the liquid from a solution is called evaporation. The liquid can be evaporated using heat from the surroundings or by heating the solution directly. before evaporation after evaporation

11. 7H Separation techniques - Evaporation In hot countries, special ponds are flooded with seawater and exposed to the heat of the sun. What happens to the water? The water evaporates and leaves the salt behind. Salt produced in this way is called solar salt. Why isn’t solar salt produced in the UK?

12. 7H Separation techniques - Rock salt Salt is also found as rock salt in layers below the ground. Rock salt can be obtained by solution mining.

13. 7H Separation techniques -Chromatography

14. 7H Separation techniques – Distillation The best method to separate and collect the solvent from a solution is distillation. Distillation involves three stages: How can you separate the solventfrom the solids dissolved in a solution? boiling condensing collecting

15. 7H Separation techniques – Distillation Where in the distillation equipment do boiling, condensing and collecting take place? thermometer Liebig condenser boiling gas cools and condenses flask with mixture water in liquid boils off water out heat one of liquids in mixture gas turned back to a liquid heat mat

16. 7H Separation techniques – Distillation The most important piece of kit for distillation is the Liebig condenser. 2. Cold water in the outer tube cools the hot gas, which condenses to become a liquid. Cold water enters the outer tube at the bottom and warm water leaves the outer tube at the top. Why does this happen? 1. Hot gas passes down the inner tube. water in water out 3. The liquid is collected at the bottom.

17. 7H Separation techniques - Summary The choice of separation technique depends on two things: 1. Is the solid soluble or insoluble? 2. Do you want to collect the solid (solute) or the liquid (solvent) from the solution?

18. 7H Separation techniques - Summary Description A…is used to separate small amounts of two or more solids which are soluble in the same solvent. B…is used to separate a soluble solid from the liquid to obtain the solute. C…is used to separate a soluble solid and a liquid to obtain the solvent. D…is used to separate an insoluble solid from a liquid. 1 Evaporation… 2 Filtration… 3 Chromatography… 4Distillation… Name Match the correct description to the separation technique.

19. 7H Solutions More about solutions

20. 7H More about solutions - Conservation of mass + Mass of water = 100g Mass of spoonful of coffee powder = 5g Mass of coffee solution = 105g A spoonful of coffee powder is added to a beaker of water. Why is the mass of the coffee solution different to the mass of water?

21. 7H More about solutions - Conservation of mass + Mass of water = 50g Mass of spoonful of sugar = 7g Mass of sugar solution = 57g The water and the sugar solution are the same colour. Why do they have different masses? A spoonful of sugar is added to a beaker of water.

22.  7H More about solutions - Particles in a solution A solid does not disappear when it dissolves to form a solution. In a solution, the particles from the solute are no longer closely packed together. They are evenly spread out between the particles of the solvent. solute + solvent solution What happens to the particles? Why is dissolving is not the same as melting?

23. 7H More about solutions- Saturated solutions and solubility How much sugar can you dissolve in a cup of tea? If you keep adding sugar to a cup of tea you end up with a very sweet drink and a gloopy mess! When a solid dissolves in a liquid to make a solution, eventually no more solid will dissolve. The solution is saturated.

24. 7H More about solutions - Solubility and temperature The total amount of a solid that can dissolve in a solution is called the solubility. What happens to the solubility of sugar as the temperature increases?