Elements, Compounds and Mixtures
Each subtopic includes About section, revision page link, 10 preview questions, and practice CTAs.
Pure and Impure Substances
SubtopicPure and Impure Substances under Elements, Compounds and Mixtures for Grade 7 ICSE.
Preview questions (no answers)
- 1.
Which of the following is the symbol for the element Iodine?
A.Io
B.Id
C.I
D.In
- 2.
The symbol 'Al' stands for:
A.Silver
B.Gold
C.Aluminum
D.Argon
- 3.
Which of the following is a diatomic molecule?
A.B.C.D. - 4.
A mixture of sand and sawdust can be separated by:
A.Magnetic separation
B.Winnowing
C.Filtration
D.Adding water and skimming
- 5.
A laboratory experiment is conducted to distinguish between a pure substance and a mixture by heating two clear liquids, A and B. Based on the observations recorded in the diagram, which conclusion is scientifically valid?
A.Liquid A is a mixture because its temperature stays constant during boiling.
B.Liquid B is a pure substance because it boils at a higher temperature than Liquid A.
C.Liquid A is a pure substance because it has a fixed boiling point, while Liquid B is a mixture because its temperature rises while boiling.
D.Both Liquid A and Liquid B must be mixtures because they both eventually change their physical state upon heating.
- 6.
A student is provided with a mixture containing Iron filings, Common Salt (), and Sand. They follow the separation scheme shown in the flowchart. What are the correct identities of 'Substance 1', 'Substance 2', and 'Substance 3'?
A.1: Salt, 2: Sand, 3: Iron filings
B.1: Iron filings, 2: Sand, 3: Salt solution
C.1: Iron filings, 2: Salt solution, 3: Sand
D.1: Sand, 2: Salt solution, 3: Iron filings
- 7.
What happens when a mixture of iron filings and sulphur powder is treated with carbon disulphide?
A.Iron dissolves in it.
B.Sulphur dissolves in it.
C.Both iron and sulphur dissolve.
D.A black substance is formed.
- 8.
Which of the following separation techniques is used to separate cream from milk?
A.Fractional Distillation
B.Centrifugation
C.Chromatography
D.Sublimation
- 9.
The total number of atoms in one molecule of is:
A.24
B.44
C.45
D.12
- 10.
Crystallization is considered a better method than simple evaporation for obtaining pure solids because:
A.It is a faster process.
B.Some solids may decompose or get charred on heating to dryness in evaporation.
C.Evaporation requires more heat.
D.Crystallization can only be used for mixtures of two liquids.
Download the worksheet for Elements, Compounds and Mixtures - Pure and Impure Substances to practice offline. It includes additional chapter-level practice questions.
Separation Techniques (Filtration, Distillation, Chromatography)
SubtopicSeparation Techniques (Filtration, Distillation, Chromatography) under Elements, Compounds and Mixtures for Grade 7 ICSE.
Preview questions (no answers)
- 1.
Which separation technique is commonly used to purify water for use in car batteries or science experiments?
A.Filtration
B.Distillation
C.Sieving
D.Chromatography
- 2.
What is the term for a substance that dissolves in a liquid?
A.Insoluble
B.Solvent
C.Soluble
D.Residue
- 3.
Which of these mixtures is best separated by distillation?
A.Alcohol and water
B.Sand and gravel
C.Oil and water
D.Pebbles and water
- 4.
In distillation, what is the role of the Bunsen burner?
A.To cool the liquid
B.To provide heat for evaporation
C.To filter the solid
D.To measure the temperature
- 5.
Which component in a filtration setup acts as the 'sieve' to separate particles?
A.The funnel
B.The beaker
C.The filter paper
D.The glass rod
- 6.
In paper chromatography, if two substances move to the same height using the same solvent, what can we likely conclude?
A.They have the same color
B.They are likely the same substance
C.One is a solid and one is a liquid
D.They are both insoluble
- 7.
Which of these processes involves both a physical change of state and a separation technique?
A.Magnetism
B.Hand-picking
C.Distillation
D.Sieving
- 8.
In the separation of a mixture of dyes, what would happen if the solvent front reached the very top of the chromatography paper?
A.The values would become impossible to calculate accurately.
B.The dyes would all move to the top and mix again.
C.The paper would dissolve.
D.The experiment would be more accurate.
- 9.
During filtration, what is the role of the 'filter cone' shape formed by the paper?
A.It increases the chemical reactivity of the paper.
B.It provides a large surface area for the liquid to pass through while keeping the solid contained.
C.It cools down the liquid.
D.It changes the color of the filtrate.
- 10.
Which of the following is a disadvantage of simple distillation compared to chromatography for analyzing complex biological mixtures?
A.Distillation is faster.
B.Distillation requires high temperatures which might decompose sensitive biological molecules.
C.Distillation cannot separate liquids.
D.Distillation only works for colored substances.
Download the worksheet for Elements, Compounds and Mixtures - Separation Techniques (Filtration, Distillation, Chromatography) to practice offline. It includes additional chapter-level practice questions.
Crystallization
SubtopicCrystallization under Elements, Compounds and Mixtures for Grade 7 ICSE.
Preview questions (no answers)
- 1.
Which of these is NOT a step in the crystallization of copper sulphate?
A.Dissolving
B.Filtration
C.Cooling
D.Distillation
- 2.
What does a 'homogeneous mixture' mean in the context of preparing for crystallization?
A.A mixture with different properties in different parts
B.A uniform solution of solute and solvent
C.A mixture of two solids
D.A mixture of oil and water
- 3.
The sharp points where the faces of a crystal meet are called:
A.Edges
B.Vertices
C.Planes
D.Liquors
- 4.
Large crystals of which of these can be grown by hanging a small seed crystal in its saturated solution?
A.Sand
B.Alum
C.Chalk
D.Wood
- 5.
Why is it important to use a clean glass rod during the crystallization test?
A.To avoid introducing new impurities that could affect crystal formation
B.To make the rod stronger
C.To help the rod boil the water
D.To change the color of the solution
- 6.
What happens to the temperature of a solution during the time it is being concentrated to reach the crystallization point?
A.It stays at the freezing point
B.It is usually kept near the boiling point of the solvent
C.It is kept at
D.It decreases continuously
- 7.
Which of the following describes the 'mother liquor'?
A.The pure water used to dissolve the salt
B.The concentrated solution of impurities and leftover solute after crystallization
C.The solid crystals formed
D.The acid added to the solution
- 8.
Why is 'fractional crystallization' often used in the industrial production of fertilizers like Potassium nitrate?
A.To ensure that only the most colorful crystals are selected.
B.To separate different salts present in the mineral ore based on their varying solubility-temperature gradients.
C.To break the crystals into smaller fractions for easier packaging.
D.To ensure that the crystals contain exactly 50% water.
- 9.
A sample of Copper sulfate crystals is heated in a dry test tube. A white powder is formed and water droplets appear on the cooler upper parts of the tube. This experiment proves that:
A.The crystals were a mixture of salt and liquid water.
B.The crystals contained 'water of crystallization' as part of their structure.
C.Copper sulfate is a liquid at room temperature.
D.Hydrogen and oxygen gas reacted inside the tube to form water.
- 10.
A student uses a 'water bath' instead of a direct flame to concentrate the solution. What is the technical advantage of this for the quality of the crystals?
A.It allows the solution to reach much higher temperatures than a flame.
B.It ensures uniform heating and prevents the decomposition of heat-sensitive compounds.
C.It adds moisture to the solution to prevent it from drying out.
D.It makes the crystallization process happen faster.
Download the worksheet for Elements, Compounds and Mixtures - Crystallization to practice offline. It includes additional chapter-level practice questions.
Types of Mixtures
SubtopicTypes of Mixtures under Elements, Compounds and Mixtures for Grade 7 ICSE.
Preview questions (no answers)
- 1.
If you mix sugar and wheat flour, the resulting mixture is:
A.Homogeneous
B.Heterogeneous
C.A compound
D.An element
- 2.
Mist is formed by droplets of water in the air. Mist is a:
A.Gas-gas mixture
B.Liquid-gas mixture
C.Solid-gas mixture
D.Solid-liquid mixture
- 3.
A mixture of pebbles and water is:
A.Heterogeneous
B.Homogeneous
C.A solution
D.An alloy
- 4.
Which of the following is a characteristic of a mixture but NOT a compound?
A.It has a definite chemical formula
B.It is always homogeneous
C.The components can be in any ratio
D.Energy is always released during its formation
- 5.
In a mixture of salt and water, if more salt is added to a saturated solution and it does not dissolve, the mixture becomes:
A.Homogeneous
B.Heterogeneous
C.A compound
D.A gas
- 6.
Which of these is a homogeneous mixture of two or more gases?
A.Clouds
B.Dusty air
C.Clean dry air
D.Steam
- 7.
A mixture of mustard oil and water can be separated using a separating funnel. This is because they are:
A.Miscible liquids
B.Immiscible liquids
C.Soluble in each other
D.Gases at room temperature
- 8.
Solder is an alloy used for joining electrical wires. It is a mixture of which two elements?
A.Zinc and Copper
B.Tin and Lead
C.Iron and Carbon
D.Aluminum and Copper
- 9.
Which of the following represents the correct classification of 'Muddy Water' left undisturbed for a long time?
A.It becomes a homogeneous solution.
B.It remains a stable colloid.
C.The suspended particles settle down due to gravity.
D.The mud particles evaporate with the water.
- 10.
If we mix iron filings and sulfur powder and heat them strongly, a black substance called Iron Sulfide is formed. Why is this final product NOT a mixture?
A.The components can still be separated by a magnet.
B.It has the same properties as Iron and Sulfur.
C.It has a fixed composition and can only be broken down by chemical means.
D.The ratio of Iron to Sulfur in it can be changed at will.
Download the worksheet for Elements, Compounds and Mixtures - Types of Mixtures to practice offline. It includes additional chapter-level practice questions.