Chemistry: Separating Mixtures
Using filtering, evaporation, and magnetism
Chemistry: Separating Mixtures
Using filtering, evaporation, and magnetism
Chemistry - Grade 4-5
- 1
A student mixes sand and water in a cup. Which method should the student use to separate the sand from the water, and why?
Think about what a coffee filter or paper towel can catch.
The student should use filtering. The filter lets the water pass through but traps the sand because sand particles are larger than the tiny holes in the filter. - 2
A cup contains salt water. The student wants to get the salt back. Which method should the student use?
The student should use evaporation. When the water evaporates, the salt is left behind because salt does not evaporate with the water. - 3
A mixture contains iron filings and sand. Which tool can separate the iron filings from the sand?
Iron is a magnetic material.
A magnet can separate the iron filings from the sand. The iron filings are attracted to the magnet, but the sand is not. - 4
Circle the mixture that could be separated by filtering: salt dissolved in water, gravel mixed with water, or sugar dissolved in tea. Explain your choice.
Gravel mixed with water could be separated by filtering. The gravel pieces are large enough to be trapped by the filter while the water passes through. - 5
A student pours muddy water through a filter. The water that comes out is clearer, but it is still a little brown. What does this show about filtering?
A filter only catches particles that are too large to pass through its holes.
This shows that filtering can remove larger solid particles, but it may not remove all tiny particles or dissolved substances from the water. - 6
A mixture has paper clips, rice, and salt. Which material can be removed first using a magnet?
The paper clips can be removed first using a magnet. Paper clips are usually made of steel, which is attracted to magnets. - 7
After removing the paper clips from a mixture of paper clips, rice, and salt, how could a student separate the rice from the salt?
Compare the size of a rice grain with the size of a salt grain.
The student could use a sieve or filter with holes large enough for salt to pass through but small enough to hold back the rice. The rice pieces are much larger than the salt grains. - 8
A student stirs sugar into warm water until the sugar disappears. Can the sugar be removed by a paper filter? Explain why or why not.
The sugar cannot be removed by a paper filter because it has dissolved in the water. Dissolved sugar particles are too small to be trapped by the filter. - 9
A teacher places a dish of salt water near a sunny window for several days. What will happen to the water and the salt?
Evaporation changes liquid water into water vapor.
The water will slowly evaporate into the air. The salt will stay in the dish and may form crystals as the water leaves. - 10
Which separation method depends on a material being attracted to a magnet: filtering, evaporation, or magnetism?
Magnetism depends on a material being attracted to a magnet. It is useful for separating magnetic metals such as iron from nonmagnetic materials. - 11
A mixture contains salt, sand, and iron filings. Write the best order of steps to separate all three materials.
Use each method for the material it works on best.
First, use a magnet to remove the iron filings. Next, add water to dissolve the salt. Then filter the mixture to remove the sand. Finally, evaporate the water to get the salt back. - 12
A student wants to separate a mixture of small plastic beads and water. Would evaporation be the best first method? Explain your answer.
Choose the method that separates the mixture most directly.
Evaporation would not be the best first method because it would take longer and only remove the water. Filtering would be faster because the beads are solid and large enough to be trapped. - 13
A magnet is held near a mixture of copper pennies, iron nails, and dry beans. Which items will the magnet most likely pick up?
The magnet will most likely pick up the iron nails. The dry beans are not magnetic, and copper pennies are not attracted strongly to magnets. - 14
Why is it important to use a container or dish when evaporating salt water to get the salt back?
The water leaves, but the salt remains as a solid.
It is important to use a container or dish so the salt stays in one place after the water evaporates. Without a container, the salt could spill or be hard to collect. - 15
A student has three mixtures: sand and water, salt water, and iron filings mixed with flour. Match each mixture to the best separation method.
Look for clues about particle size, dissolved substances, and magnetic materials.
Sand and water should be separated by filtering. Salt water should be separated by evaporation. Iron filings mixed with flour should be separated by magnetism.