Elements, Compounds and Mixtures | ICSE Class 6 Chemistry Notes

This note covers elements, atoms and molecules, symbols of the first twenty elements, metals and non-metals, compounds and their formulae, mixtures, differences between mixtures and compounds, and separation by sieving, sedimentation, decantation, filtration, evaporation, magnetic separation and sublimation.

How is matter classified into elements, compounds and mixtures?

Matter is anything that has mass and occupies space. Mass means the quantity of matter in an object. The materials around us occur as solids, liquids or gases. Their physical state describes their form, but it does not by itself tell us their chemical composition.

Composition means what a material contains. Chemically, matter can be classified into elements, compounds and mixtures. In nature, matter occurs mostly in the form of mixtures. To classify a sample, consider the substances present and whether its different elements are chemically combined.

What does a pure substance contain?

A pure substance contains the same type of particles throughout, with no other substance mixed into it. A particle is a tiny constituent of matter. Pure substances include both elements and compounds. Purity therefore does not mean that a substance must contain just one element.

An atom is a tiny particle of an element. At this level, an element is described as being made of identical atoms. A chemical change forms a new substance. A physical process, such as separating sand from water, does not change the separated substances into new ones.

Water illustrates why classification needs care. Pure water is a compound even though it contains different elements. Sugar dissolved in water is a mixture because sugar and water are present together. Merely looking clear does not establish that a liquid is a pure substance.

What are elements, atoms and molecules?

Definition: An element is a substance made up of identical atoms. It cannot be broken down into simpler substances by chemical methods.

Iron contains iron atoms, while sulphur contains sulphur atoms. The atoms of one element differ from those of another element. Iron powder, sulphur powder and zinc granules are examples of elements. Powder and granules describe the form of a sample, rather than a different chemical category.

Can a molecule contain more than one atom and still be an element?

The atoms of most elements cannot exist independently. Two or more such atoms combine to form a stable particle called a molecule. A molecule of an element contains atoms of the same element. Having several atoms does not, by itself, make something a compound.

Hydrogen has the symbol H, oxygen has the symbol O, and nitrogen has the symbol N. A symbol is the short notation used for an element. A formula uses symbols and numbers to represent a substance. The small lower number in a formula is a subscript; it tells us how many atoms of the preceding element are represented.

Each formula above represents a molecule with two atoms of one element. None represents a compound. The important distinction is between the number of atoms and the number of different elements: two oxygen atoms still belong to just one element, oxygen.

When reading a particle model, first identify the kinds of atoms represented. Then consider which atoms are joined. This separates the question “How many atoms are there?” from the question “How many different elements are there?”

How are element symbols written, and what are the first twenty?

Chemical symbols provide a short, internationally recognised way to write element names. The first letter is a capital letter. A second letter, when present, is a small letter. Thus aluminium is written Al, with a capital A and a small l.

Many symbols use the first letter or the first two letters of the element's name. Others use its first letter and a later letter: chlorine is Cl, and zinc is Zn. The symbol is a fixed notation, not an abbreviation that can be freely changed.

Why do some symbols differ from their English names?

Some symbols come from older names in other languages. Sodium is Na from natrium, potassium is K from kalium, and iron is Fe from ferrum. These are the Latin names associated with those symbols. Iron and zinc are also useful symbols for the examples in this chapter.

The periodic table is the organised table of elements. Learn the following twenty names together with their symbols. Read each capital and small letter carefully, particularly where two names begin with the same letter.

Read down the first pair of columns from hydrogen to neon, then down the second pair from sodium to calcium. A two-letter symbol represents one element: He means helium, not a combination of two different elements.

Note: Keep symbols and molecular formulae distinct. O names oxygen and can represent an oxygen atom; O₂ represents a molecule containing two oxygen atoms. The subscript does not change the element's identity.

How do the properties of metals and non-metals differ?

Elements can be grouped as metals and non-metals using their properties. Metals are generally hard, lustrous, malleable, ductile, and good conductors of heat and electricity. Iron, aluminium and copper are metals. Sulphur, carbon, hydrogen and oxygen are non-metals.

What do these property names mean?

Lustre means shine; the shine shown by metals is called metallic lustre. Malleability is the ability to be beaten into thin sheets. Ductility is the ability to be drawn into wires. Most metals possess malleability, and ductility is mainly possessed by metals.

Sonority is the ability to produce a ringing sound when struck. A conductor allows heat or electricity to pass through it. A good conductor of electricity allows electricity to flow through it easily. These properties describe behaviour, rather than simply appearance.

A material that breaks into pieces when hammered is brittle. Sulphur is brittle rather than malleable. This comparison gives a direct way to distinguish the behaviour of the sample from the behaviour of the metal samples.

Why should general properties not be treated as absolute rules?

Sodium and potassium are soft metals that can be cut with a knife. Mercury is a metal that is liquid at room temperature. These examples show why “metals are generally hard” is more accurate than “all metals are hard”.

A description should therefore name the property being compared and retain words such as “generally” and “most”. A single property should not be stretched into a claim that every member of a group behaves identically.

What are compounds, and how do their formulae show composition?

Definition: A compound forms when two or more different elements combine chemically in fixed, definite proportions. The resulting substance has properties different from those of its constituent elements.

Constituent elements are the elements making up a compound. Water contains hydrogen and oxygen chemically combined. It is a pure substance when no other substance is mixed into it. Its constituent elements cannot be separated by a physical method such as filtration.

How do we read a chemical formula?

A chemical formula uses element symbols and subscripts to show composition. In a molecular formula, these show the kinds and numbers of atoms in a molecule. Where a symbol has no subscript, one atom of that element is represented.

In H₂O, H means hydrogen and O means oxygen. One water molecule contains two hydrogen atoms and one oxygen atom. A ratio compares quantities in order, so a hydrogen-to-oxygen atom ratio of 2:1 means two hydrogen atoms for every one oxygen atom.

Calcium oxide and zinc chloride are represented here by their formula ratios. Their formulae need not be described as separate molecules. For water, carbon dioxide and nitrogen dioxide, the molecular formula directly describes the atoms in one molecule.

How is a compound different from its elements?

Hydrogen is a fuel, meaning a substance that can burn, and oxygen supports burning. Water has different properties from either constituent. The chemically combined substance must be studied as a substance in its own right, rather than as its separate elements.

Notice that O₂ has two oxygen atoms and is an element, while CO₂ contains carbon and oxygen and is a compound. The number of different element symbols, not merely the presence of a subscript, explains the difference in these examples.

What makes a mixture different from a compound?

A mixture contains two or more substances mixed together without reacting chemically with one another. Its individual substances are called components. The components retain their properties, and their relative amounts can vary. Sugar solution, honey and milk are examples of mixtures.

A solution is a uniform mixture in which a substance is dissolved in another. Uniform means having the same composition throughout. In sugar solution, sugar is the dissolved substance and water is the liquid in which it dissolves. Dissolving does not mean that sugar has ceased to exist.

How do proportions and properties help us distinguish them?

Concentration describes the amount of dissolved substance in a given amount of solution or of the substance used to dissolve it. Different sugar solutions can contain different relative amounts of sugar and water. This variable composition is consistent with their being mixtures.

The phrase “any proportion” distinguishes mixtures from fixed-composition compounds. It does not mean that unlimited sugar must dissolve in a fixed amount of water. The amount that can dissolve is limited under given conditions.

Visibility alone is also insufficient for classification. Sugar and water cannot be seen separately in their uniform mixture. By contrast, the components of an iron and sulphur mixture remain distinguishable. Both are mixtures because their formation leaves the component substances present.

For a clear explanation, link the classification to evidence: variable proportions and retained component properties support “mixture”; fixed proportions and the formation of a new substance support “compound”.

What does the iron and sulphur activity show?

Iron and sulphur provide a direct comparison between mixing and chemical combination. Iron filings are small pieces of iron. Sulphur powder is yellow. A magnetic substance is attracted by a magnet; iron is magnetic, whereas sulphur is not attracted in this activity.

What happens before heating?

When iron filings and sulphur powder are mixed, both remain present. Their particles can still be distinguished, and the iron retains its response to a magnet. Moving a magnet over the mixture attracts the iron, allowing it to be separated from the sulphur.

This is magnetic separation, the separation of a magnetic substance from a non-magnetic substance using a magnet. It works because the components differ in their response to the magnet. Merely stating that one component is a solid would not explain why this method works.

What changes after chemical combination?

On heating iron and sulphur together appropriately, a black compound called iron sulphide forms. Its formula is FeS: Fe represents iron and S represents sulphur. The new substance is not attracted by a magnet in this demonstration, so the magnet cannot extract its combined iron.

1. Observe the iron and sulphur separately and identify their properties.
2. Mix them and observe that their particles remain distinguishable.
3. Test the mixture with a magnet and observe the iron being attracted.
4. Compare it with the cooled iron sulphide formed in a supervised heating demonstration.

The heating demonstration should take place under supervision in a fume hood or a well-ventilated area, without inhaling gases. A fume hood is an enclosure that extracts laboratory fumes. The comparison concerns a new substance, rather than a mixture that merely looks darker.

The key conclusion is that retained properties distinguish the unheated mixture from the compound. Heating alone is not the evidence: the formation of iron sulphide with different properties is the evidence of chemical change.

How do we choose a separation method, and when does sieving work?

A separation method must use a difference between the properties of a mixture's components. First identify what is mixed and which component is wanted. Then choose a process that acts differently on the components, such as a sieve for particles of different sizes.

Sieving separates solid particles of different sizes using a sieve. A sieve has holes that allow smaller particles through while retaining larger ones. Rice powder mixed with stones is an example: the holes must let the powder pass but hold back the stones.

Insoluble means not dissolving in the liquid concerned. Vapour is the gaseous form of a substance. Sedimentation means settling; decantation means pouring away the upper liquid. Filtration uses a filter, evaporation changes liquid into vapour, and sublimation changes solid directly into vapour.

Which property supports each method?

These properties matter because a method suitable for undissolved sand is not necessarily suitable for dissolved salt. Identify the relevant difference before naming a method, then explain what happens to each component during separation.

The photograph shows hands holding a sieve above a metal plate containing fine flour. The sieve and collecting plate show where material is separated and where the fine particles are collected.

See Fig. 9.5 in your NCERT textbook

If sieve holes are too large, both components may pass through. If they are too small, the powder may be retained as well. Choosing a suitable hole size is therefore part of choosing the method, rather than an unrelated detail.

How do sedimentation and decantation separate a solid from a liquid?

Sedimentation is the settling of a heavier insoluble component at the bottom of a liquid. The settled material is called the sediment. In a sand and water mixture, leaving the container undisturbed allows the sand to settle below the water.

Decantation is the gentle pouring off of the liquid by tilting the vessel, while leaving the settled solid behind. Sedimentation and decantation are related but distinct: one produces the settled layer, and the other removes the liquid above it.

What sequence should be followed?

1. Place the mixture of sand and water in a container.
2. Leave it undisturbed so that the heavier insoluble sand can settle.
3. Observe the liquid above the settled sand before moving the container.
4. Tilt the container gently and pour the upper liquid into another vessel, leaving the sediment behind.

The reason for waiting is that the solid must settle before the upper liquid can be poured away effectively. Pouring or stirring vigorously can mix the settled particles back into the liquid. The operation depends on maintaining the separation that settling has produced.

What does tea brewing illustrate?

After tea containing tea leaves stands undisturbed, gentle pouring can remove most of the leaves from the poured tea by leaving them in the vessel. Decantation does not completely separate all the tea leaves. Some can still accompany the liquid.

This limitation explains why a strainer can be preferable. A strainer provides a barrier that holds back the leaves while the tea passes through. Settling and pouring alone do not provide that same barrier.

Do not expect dissolved salt to settle like sand. Sedimentation requires an insoluble component that settles. A successful description should therefore include both the observed settling and the careful removal of the upper liquid, rather than simply saying that the mixture is poured out.

How does filtration work, and what are residue and filtrate?

Filtration separates an insoluble solid from a liquid by passing the mixture through a filter. A filter contains small openings called pores. Liquid can pass through suitable pores, while the solid particles being separated remain on the filter.

The solid retained is the residue. The liquid that passes through and is collected below is the filtrate. These terms refer to the positions of the separated materials: residue stays on the filter; filtrate passes through it.

How is filter paper used?

1. Fold a circular filter paper to form a cone.
2. Place the paper cone inside a funnel supported above a collecting vessel.
3. Pour the mixture into the filter paper so that it passes through the paper.
4. Observe the retained solid on the paper and collect the liquid below.

A funnel has a wide upper opening and a narrow stem that directs liquid into a vessel. A conical flask is a collecting vessel with a broad base and narrow neck; a tripod stand is a three-legged support.

In filtering sand and water, sand remains as residue and water is collected as filtrate. Filtering muddy water similarly leaves mud on the paper in the illustrated activity.

The photographs show filter paper fitted inside a funnel, followed by muddy water in the funnel supported on a tripod stand above a conical flask. Labels identify the filter paper, funnel, muddy water, tripod stand and conical flask.

See Fig. 9.11 in your NCERT textbook

Why does the choice of filter matter?

A tea strainer retains tea leaves, but finer particles require smaller pores. Cloth has openings between its woven threads, and filter paper has very fine pores. The choice of filter depends on the size of the particles to be removed.

Ordinary filtration does not recover dissolved salt from salt solution. The dissolved substance passes through with the liquid. Thus a clear filtrate need not be a pure substance: clarity describes what is visible, whereas purity concerns the substances present.

How does evaporation recover salt from salt water?

Evaporation is the conversion of a liquid into its vapour. It can separate a dissolved solid from a liquid. In salt water, the water changes into water vapour and the salt remains behind. The salt has been recovered from a mixture.

What observations show the separation?

A few drops of salt solution spread on dark paper leave salt behind when the water evaporates. The solid becomes visible after drying. Its reappearance shows that dissolving the salt did not destroy it or change the mixture into a new compound.

In a heating demonstration, salt solution is placed in a china dish, a heat-resistant laboratory dish. The water is allowed to boil away, and the dish is left to cool. Salt is then observed in the dish. Care is needed while heating and handling the dish.

How is salt obtained from seawater?

Seawater contains salts and other dissolved substances. It is held in shallow pits and exposed to sunlight and air. As the water evaporates, a solid mixture remains. Common salt is obtained from that mixture by further purification.

This last step matters: evaporating seawater does not directly guarantee pure common salt. The liquid originally contained more than one dissolved substance. The remaining material must therefore be described as a solid mixture until the required salt is purified.

Evaporation suits the aim of obtaining salt from salt water. In the open dish, the water leaves as vapour rather than being collected as liquid water. State which component is recovered when explaining this method, and distinguish it from filtering out an undissolved solid.

How does sublimation separate solids, and how is it different from evaporation?

Sublimation is the direct change of a solid into vapour without passing through the liquid state. Camphor changes in this way on heating below its melting point. The melting point is the temperature at which a solid changes into a liquid.

Deposition is the reverse change: vapour becomes solid directly without becoming liquid. In a separation using sublimation, one component enters the vapour state and can form a solid deposit on a cooler surface. The other solid remains behind under these conditions.

How can camphor be separated from sand?

A mixture of crushed camphor and sand is placed in a clean, dry china dish. A dry glass funnel is placed upside down over it, with a cotton plug in the funnel's nozzle. The nozzle is the narrow opening at the end of the funnel stem.

Gentle heating causes camphor to sublime while sand stays in the dish. On the cooler inner wall of the funnel, the vapour changes back into solid camphor. You may find white solid deposits there. The observed deposit and the remaining sand occupy different parts of the apparatus.

The drawing shows an inverted glass funnel with a cotton plug above a china dish containing camphor and sand. The dish rests on wire gauze supported by a tripod stand, with a burner underneath.

See Fig. 5.17 in your NCERT textbook

Wire gauze is a wire mesh used to support the dish during heating on the tripod stand. The burner supplies heat. The arrangement links each piece of equipment to heating the mixture or collecting the separated solid.

Iodine crystals, ammonium chloride, naphthalene and camphor are substances used when studying sublimation. The separation works when their behaviour differs from that of the other component. It is not a method for every pair of solids.

Keep the starting states clear: evaporation starts with a liquid, while sublimation starts with a solid. Both produce vapour, but only sublimation avoids the liquid state altogether. This distinction explains why salt water and camphor mixed with sand require different descriptions.

Glossary

• Element — A pure substance made of one kind of atom that cannot be chemically broken into simpler substances.
• Atom — A tiny particle of an element, distinct from atoms belonging to other elements.
• Molecule — A stable particle formed when atoms combine; its atoms may belong to the same or different elements.
• Chemical symbol — A short notation representing an element, beginning with a capital letter.
• Compound — A substance formed by different elements chemically combining in fixed proportions, with properties different from its elements.
• Mixture — Two or more substances present together without chemical combination, with the components retaining their properties.
• Component — One of the individual substances that together make up a mixture.
• Sieving — Separation of solid particles of different sizes by using suitably sized holes in a sieve.
• Sedimentation — The settling of a heavier insoluble component at the bottom of a liquid.
• Decantation — Gentle removal of an upper liquid by tilting a vessel while leaving settled material behind.
• Filtration — Separation of an insoluble solid from a liquid using a filter with suitable pores.
• Residue — The solid material retained on the filter during the process of filtration.
• Filtrate — The liquid that passes through a filter and is collected in a vessel below.
• Evaporation — Conversion of a liquid into vapour, used to recover a dissolved solid from a liquid.
• Sublimation — Direct conversion of a solid into vapour without passing through the liquid state.

Common errors and misconceptions

• Misconception: Every molecule containing two atoms is a compound. Correct: Oxygen molecules contain two atoms of the same element. A compound contains different elements chemically combined.
• Misconception: A compound cannot be a pure substance. Correct: Both elements and compounds can be pure substances. A compound's different elements are chemically combined in fixed proportions.
• Misconception: The capitalisation of a symbol does not matter. Correct: The first letter is capital and the second, if present, is small. Aluminium is Al.
• Misconception: All metals are hard solids. Correct: Metals are generally hard; sodium and potassium are soft, and mercury is liquid at room temperature.
• Misconception: A magnet removes iron from iron sulphide. Correct: It separates iron from an iron and sulphur mixture. Iron sulphide is a new compound with different properties.
• Misconception: Filtration recovers dissolved salt from salt water. Correct: Dissolved salt passes through an ordinary filter with water. Evaporation leaves salt behind.
• Misconception: Decantation completely removes tea leaves. Correct: Gentle pouring after settling removes most leaves, but some may remain in the poured tea.
• Misconception: Evaporation and sublimation are identical. Correct: Evaporation starts with a liquid. Sublimation changes a solid directly into vapour without an intermediate liquid state.

Exam-style questions with model answers

Q1. An oxygen molecule contains two oxygen atoms. A water molecule contains two hydrogen atoms and one oxygen atom. Classify oxygen and water as an element or compound, giving a reason for each. [2 marks]

1. Oxygen is an element because its molecule contains atoms of only one element, oxygen.
2. Water is a compound because its molecule contains two different elements, hydrogen and oxygen, chemically combined.

Q2. Aluminium has the symbol Al, sodium has the symbol Na from the Latin name natrium, and oxygen molecules have the formula O₂. Explain one point about capitalisation, one about the origin of a symbol, and one about the meaning of the subscript. [3 marks]

1. In Al, the first letter is capital and the second letter is small. This illustrates the rule for writing a two-letter element symbol.
2. Na comes from natrium, sodium's Latin name. An element's symbol therefore need not follow the opening letters of its English name.
3. The subscript ₂ in O₂ represents two oxygen atoms in one oxygen molecule. It does not mean that the molecule contains two different elements.

Q3. Iron and sulphur can be mixed in variable proportions while retaining their properties. Iron sulphide forms by chemical combination in fixed proportions and has different properties. Compare the mixture and compound under formation, proportions, and properties. [3 marks]

1. The mixture forms by bringing iron and sulphur together without chemical combination. Iron sulphide forms when these different elements chemically combine to produce a new substance.
2. The relative amounts of iron and sulphur in the mixture can vary. In iron sulphide, the constituent elements are present in fixed, definite proportions.
3. The mixture retains the properties of its components. Iron sulphide has properties different from those of the original iron and sulphur.

Q4. Sand is insoluble in water and settles when left undisturbed. Describe sedimentation followed by decantation to separate this mixture in four steps. [4 marks]

1. Place the sand and water mixture in a container and leave it undisturbed, rather than continuing to stir the sand through the water.
2. Allow the heavier insoluble sand to settle at the bottom. This settling stage is sedimentation, and the settled sand forms the sediment.
3. Gently tilt the vessel and pour the upper water into another container. This removal of the upper liquid is called decantation.
4. Leave the sand behind without disturbing the settled layer. Gentle pouring helps prevent the sand from being carried over with the water.

Q5. Sand does not dissolve in water. Suitable filter paper retains sand while allowing water to pass. Given filter paper, a funnel, a support and a collecting vessel, explain filtration in five points, including the names and locations of both separated materials. [5 marks]

1. Fold the filter paper into a cone and place it inside the funnel. The paper provides the porous barrier that separates the insoluble sand from water.
2. Support the funnel over the collecting vessel. This arrangement provides a path for the water passing through the paper to enter the vessel underneath.
3. Pour the sand and water mixture into the paper cone. The mixture must pass through the filter paper for the separation to take place.
4. The sand remains on the filter paper because the stated filter retains its particles. This retained solid is called the residue.
5. The water passes through the paper and funnel into the collecting vessel. This collected liquid is the filtrate; the sand and water now occupy different locations.

Q6. Choose a separation method and explain it for each mixture: rice powder and larger stones, using a sieve that passes powder but retains stones; iron and sulphur, where only iron is attracted by a magnet; and salt water, where water vaporises and salt remains. [3 marks]

1. Use sieving for rice powder and stones. The powder passes through the suitable holes, while the larger stones remain on the sieve because of their size.
2. Use magnetic separation for iron and sulphur. A magnet attracts the iron from the mixture while the sulphur remains behind because it is not attracted.
3. Use evaporation for salt water. Water changes into vapour and leaves the dissolved salt behind, allowing the solid salt to be recovered from the mixture.

Q7. Camphor changes directly from solid to vapour on gentle heating, while sand does not. Camphor vapour becomes solid on a cooler surface. Explain how a china dish and an inverted glass funnel can separate this mixture, giving five points. [5 marks]

1. Place the mixture of camphor and sand in a clean, dry china dish. The dish holds both solid components together at the start of the separation.
2. Position the inverted glass funnel over the dish. Its inner wall provides the cooler surface on which the separated camphor can later collect as a solid.
3. Heat the mixture gently. Camphor changes directly from a solid into vapour, without becoming liquid, and this change of state is called sublimation.
4. Sand does not undergo that change under the stated conditions, so it remains in the china dish while camphor leaves the mixture as vapour.
5. The camphor vapour becomes solid on the cooler funnel surface by deposition. Camphor and sand can therefore be collected from different parts of the apparatus.

Q8. On evaporating seawater, water leaves as vapour and a solid mixture of salts and other substances remains. Why is “evaporation directly gives pure common salt” incorrect, and what further step is required? [2 marks]

1. The remaining solid is still a mixture because seawater contains salts and other substances, rather than common salt alone.
2. Further purification is required to obtain common salt from the solid mixture left after evaporation.

Key takeaways

• Elements contain one kind of atom; compounds contain different elements chemically combined in fixed proportions with different properties.
• A molecule can contain several atoms of the same element, so the presence of two atoms does not establish a compound.
• Element symbols begin with a capital letter, and any second letter is small; some symbols come from Latin names.
• Mixtures retain their component substances, and their proportions can vary; visible uniformity does not establish chemical purity.
• Choose a separation method by identifying a useful difference between the properties of the components.
• Sedimentation settles an insoluble solid, decantation pours away the upper liquid, and filtration retains solid particles on a filter.
• Evaporation recovers salt from salt water, while sublimation can separate camphor from sand through a direct solid-to-vapour change.
• A magnet separates iron from an iron and sulphur mixture, but cannot extract the combined iron from iron sulphide.

Test yourself

Why is O₂ an element even though it contains two atoms?

Both atoms are oxygen atoms. The molecule contains only one kind of element, rather than different elements chemically combined.

What does the subscript in H₂O tell you?

It shows two hydrogen atoms in one water molecule. Oxygen has no subscript, so one oxygen atom is represented.

What are the symbols of sodium, potassium, calcium and iron?

Sodium is Na, potassium is K, calcium is Ca, and iron is Fe.

Why is “all metals are hard” incorrect?

Metals are generally hard, but sodium and potassium are soft metals that can be cut with a knife.

Where are the residue and filtrate found after filtering sand and water?

Sand is the residue on the filter paper. Water is the filtrate collected in the vessel below.

Why does ordinary filtration fail to recover dissolved salt?

The dissolved salt passes through the filter with water. Evaporation can recover it by removing water as vapour.

Why must a sieve have suitable holes?

The holes must allow smaller particles through while retaining larger ones. Otherwise the intended separation may fail.

What is the difference between sublimation and deposition?

Sublimation changes solid directly into vapour. Deposition changes vapour directly into solid, without an intermediate liquid state.