Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
A mixture is formed when two or more substances are combined together but are not chemically joined. They can usually be separated back into their original parts.
The method used to separate a mixture depends on the properties of the materials, such as their size, whether they dissolve (solubility), or if they are magnetic.
Sieving is used to separate solids of different sizes. Small particles pass through the holes of the sieve, while larger particles stay behind.
Filtration is used to separate an insoluble solid (like sand) from a liquid (like water). The solid left on the filter paper is called the residue, and the liquid that passes through is the filtrate.
Evaporation is used to separate a soluble solid (like salt) from a liquid. When the mixture is heated, the liquid turns into gas (water vapor), leaving the solid behind.
Magnetic Separation is used when one of the materials in a mixture is magnetic (like iron or steel) and the others are not.
Decanting is a simple method of pouring off a liquid from a mixture after the solid has settled at the bottom.
📐Formulae
💡Examples
Problem 1:
How would you separate a mixture of sand and water?
Solution:
Use the process of filtration.
Explanation:
Place filter paper in a funnel over a jar. Pour the sand and water mixture into the funnel. The water passes through the tiny holes in the paper (filtrate), but the sand particles are too large and stay on the paper (residue).
Problem 2:
A student has a bowl containing small iron nails and plastic beads. What is the quickest way to separate them?
Solution:
Use a magnet.
Explanation:
Since iron is a magnetic material and plastic is not, the magnet will attract all the iron nails, leaving the plastic beads behind in the bowl.
Problem 3:
How can you get salt back from a mixture of salt and water?
Solution:
Use evaporation.
Explanation:
Pour the salt water into a shallow dish and heat it or leave it in a warm place. The water will evaporate into the air as water vapor, leaving the solid salt crystals behind in the dish.
Problem 4:
A chef needs to separate large chunks of vegetables from a soup broth. Which tool should be used?
Solution:
A sieve or a strainer.
Explanation:
The liquid broth will pass through the holes of the sieve, while the larger vegetable pieces will be caught. This works because of the difference in size between the materials.