Q1. easy
The substance from which an object is made is called its:
- A Material
- B Shape
- C Colour
- D Weight
Answer: A — Material
A material is the substance used to make an object. For example, a chair may be made of the material wood, plastic or metal.
🧪 Chemistry · Topic 1 of 10
Materials & Their Properties — Chemistry Questions with Answers
Start with the study notes on Materials & Their Properties (definitions, examples and a quick revision), then work through 60 practice questions, each with the correct answer and a clear explanation of why it is right. When you are ready, take this topic as an interactive quiz to test yourself.
Topic overview
Materials and Their Properties – what things are made of
1. Objects and materials
A material is the substance an object is made from.
- One material can make many objects: wood is used for chairs, tables, doors and pencils.
- One object can be made from many materials: a tumbler can be glass, plastic, steel or even paper.
We choose a material for a job by looking at its properties: how it looks, how hard it is, whether it dissolves, whether light passes through it, and so on.
2. Appearance and lustre
Lustre is the shine on the surface of a material. Most metals are lustrous.
Examples:
- Gold, silver and copper ornaments shine when polished.
- Iron and silver slowly look dull because air and moisture form a layer on their surface (rust or tarnish). Rubbing removes it.
3. Hard, soft, flexible and brittle
- Hard materials resist scratching and pressing, e.g. iron and stone. Diamond is the hardest natural substance.
- Soft materials are easily pressed or scratched, e.g. sponge, cotton, rubber.
- Flexible materials bend without breaking, e.g. rubber and thin wire.
- Brittle materials break instead of bending, e.g. glass and chalk.
Example: A cricket ball is not made of glass, because glass is brittle and would shatter.
4. Transparent, translucent and opaque
- Transparent: we see clearly through them, e.g. glass, clear plastic, water.
- Translucent: we see only blurred shapes, e.g. butter paper, frosted glass.
- Opaque: we cannot see through them at all, e.g. wood, metal, cardboard.
Example: Window panes are made of glass because it is transparent and hard.
5. Soluble and insoluble
A soluble substance dissolves completely in water. An insoluble substance does not dissolve.
Examples:
- Soluble: salt, sugar, glucose.
- Insoluble: sand, chalk powder, sawdust. Chalk settles at the bottom of the glass.
Solute, solvent and solution
When sugar dissolves in water, the sugar is the solute, the water is the solvent, and the mixture is a solution.
- Water dissolves so many substances that it is called the universal solvent.
- A saturated solution cannot dissolve any more solute at that temperature.
- Heating usually lets more solid dissolve; sugar dissolves faster in hot tea.
Remember: Dissolved salt is still there, even though you cannot see it. Evaporate the water and the salt is left behind.
6. Liquids that do or don't mix
Liquids that mix completely are miscible. Liquids that form separate layers are immiscible.
Examples:
- Miscible with water: vinegar, lemon juice, milk.
- Immiscible with water: coconut oil and other oils, which float as a layer on top.
Some gases dissolve in water too. Fish breathe the oxygen dissolved in water.
7. Floating and sinking
Whether something floats depends on its density compared with water. Objects less dense than water float; objects denser than water sink.
Examples:
- Wood, thermocol and oil float; stones, coins and iron nails sink.
- A huge iron ship floats because it is hollow. It pushes aside a lot of water, so its overall density is less than water's.
8. Conductors and insulators
Conductors let heat or electricity pass easily; most metals are good conductors. Insulators do not, e.g. wood, plastic, rubber, glass and air.
Examples:
- Cooking pots are metal so heat reaches the food, but their handles are plastic or wood so we can hold them.
- Electric wires are copper or aluminium inside and plastic outside.
9. Metals and non-metals
- Metals are usually lustrous, hard, malleable (can be beaten into sheets), ductile (can be drawn into wires), sonorous (ring when struck) and good conductors.
- Non-metals are usually dull, brittle and poor conductors, e.g. sulphur.
Examples:
- Aluminium foil shows malleability; copper wire shows ductility; temple bells show sonority.
- Mercury is unusual: it is a metal that is liquid at room temperature.
10. Natural and synthetic materials, and classification
Natural materials come from plants, animals or the earth, e.g. cotton, wood, wool, silk. Synthetic materials are made in factories from chemicals, e.g. plastic, nylon, polyester.
Classification means grouping materials with similar properties. It makes them easier to study, and helps us predict how a new material will behave.
Example: Raincoats are made of plastic because it is waterproof; cotton and paper soak up water.
11. Common misconceptions
| Misconception | Correct understanding |
|---|---|
| Every metal object is hard and solid. | Mercury is a liquid metal; sodium is soft enough to cut with a knife. |
| Dissolved salt disappears completely. | It is still in the water; evaporating the water leaves it behind. |
| Heavy things always sink. | Floating depends on density and shape; a huge iron ship floats. |
| Oil dissolves in water if stirred hard enough. | Oil and water are immiscible; they always separate into layers. |
| Plastic is used for everything because it is strongest. | Materials are chosen for the property a job needs, not just strength. |
12. Quick revision
- Material
- The substance an object is made of.
- Lustre
- The shine on a material's surface.
- Soluble
- Dissolves completely in water, e.g. salt.
- Solvent
- The liquid that does the dissolving, e.g. water.
- Saturated solution
- Cannot dissolve any more solute at that temperature.
- Immiscible
- Liquids that do not mix, e.g. oil and water.
- Malleable
- Can be beaten into thin sheets.
- Ductile
- Can be drawn into thin wires.
13. Test your understanding
Give one object that can be made from three different materials.
Show answer
A tumbler: glass, plastic or steel (or a chair: wood, plastic or metal).
Why does silver jewellery lose its shine?
Show answer
Air reacts with its surface and forms a dull layer, which polishing removes.
Classify butter paper, glass and wood.
Show answer
Translucent, transparent and opaque.
In salt water, which is the solute and which the solvent?
Show answer
Salt is the solute; water is the solvent.
How can you get the salt back from salt water?
Show answer
Evaporate the water; the salt is left behind.
Why does oil float on water?
Show answer
It is less dense than water and does not mix with it.
Why is a cooking pot metal but its handle plastic?
Show answer
Metal conducts heat to the food; plastic insulates, so the handle stays cool.
Which metal is liquid at room temperature?
Show answer
Mercury.
Key takeaway: Every material has its own set of properties, and those properties decide what we use it for.
Notes written by Velnov for Class 6–8 students, following the topics of the NCERT science syllabus.
Key concepts in this topic
Easy questions (1)
Medium questions (31)
Q2. medium
Different objects can be made from the same material, and the same object can be made from different materials. A tumbler can be made of:
- A Glass, plastic, steel or paper
- B Only glass
- C Only plastic
- D Only metal
Answer: A — Glass, plastic, steel or paper
The same object (a tumbler) can be made from many materials - glass, plastic, steel, even paper. The material chosen depends on the properties needed, such as strength or transparency.
Q3. medium
Materials that have a shine on their surface are said to have:
- A Lustre
- B Hardness
- C Solubility
- D Density
Answer: A — Lustre
Lustre is the shine seen on the surface of a material. Metals like gold, silver, copper and iron are lustrous, which is why they are polished to look shiny.
Q5. medium
Materials through which things can be seen CLEARLY are called:
- A Transparent
- B Opaque
- C Translucent
- D Lustrous
Answer: A — Transparent
Transparent materials (glass, clear plastic, air, water) let light pass through completely, so objects behind them can be seen clearly.
Q6. medium
Materials through which we CANNOT see at all are called:
- A Opaque
- B Transparent
- C Translucent
- D Soluble
Answer: A — Opaque
Opaque materials such as wood, cardboard, metal and stone do not allow light to pass through, so nothing can be seen through them.
Q8. medium
Materials that can be compressed or scratched easily are said to be:
- A Soft
- B Hard
- C Lustrous
- D Soluble
Answer: A — Soft
Soft materials like sponge, cotton and rubber can be compressed or scratched easily. Hard materials like iron and stone resist being scratched or compressed.
Q10. medium
Substances that dissolve completely in water are said to be:
- A Soluble
- B Insoluble
- C Opaque
- D Lustrous
Answer: A — Soluble
Soluble substances like salt and sugar dissolve in water and disappear from view, forming a solution. Insoluble substances like sand and chalk powder do not dissolve.
Q11. medium
Which of the following is INSOLUBLE in water?
- A Sand
- B Sugar
- C Salt
- D Glucose
Answer: A — Sand
Sand does not dissolve in water - it settles at the bottom, so it is insoluble. Sugar, salt and glucose all dissolve, so they are soluble.
Q13. medium
Which of these liquids does NOT mix with water?
- A Coconut oil
- B Vinegar
- C Lemon juice
- D Milk
Answer: A — Coconut oil
Oil does not mix with water - it forms a separate layer on top because it is immiscible with water. Vinegar, lemon juice and milk mix with water.
Q15. medium
Objects that FLOAT on water are usually:
- A Lighter (less dense) than water
- B Heavier than water
- C Always made of metal
- D Always transparent
Answer: A — Lighter (less dense) than water
Objects less dense than water float, while denser objects sink. Wood, thermocol, plastic and oil float on water; iron nails and stones sink.
Q17. medium
Grouping materials with similar properties together is called:
- A Classification (sorting into groups)
- B Separation
- C Dissolving
- D Melting
Answer: A — Classification (sorting into groups)
Classification is grouping objects or materials based on shared properties. It makes study easier - for example, grouping all metals together, or all soluble substances together.
Q19. medium
Which property makes metals suitable for making electrical wires?
- A They conduct electricity well
- B They are transparent
- C They are soluble
- D They are soft
Answer: A — They conduct electricity well
Metals like copper and aluminium are good conductors of electricity, so they are drawn into wires. Their ductility (ability to be drawn into wires) also helps.
Q22. medium
Which of these is a property of MOST metals?
- A Lustrous, hard, malleable, ductile and good conductors
- B Dull, soft and non-conducting
- C Transparent and soluble
- D Always liquid
Answer: A — Lustrous, hard, malleable, ductile and good conductors
Most metals are lustrous (shiny), hard, malleable, ductile, sonorous, and good conductors of heat and electricity. Non-metals usually show the opposite properties.
Q24. medium
Which of these materials is a good conductor of HEAT?
- A Aluminium
- B Wood
- C Plastic
- D Rubber
Answer: A — Aluminium
Metals like aluminium, copper and iron conduct heat well, which is why cooking utensils are made of them. Wood, plastic and rubber are poor conductors (insulators).
Q26. medium
A solution formed when a substance dissolves in a liquid has the dissolving liquid called the:
- A Solvent
- B Solute
- C Mixture
- D Residue
Answer: A — Solvent
In a solution, the substance that dissolves is the solute (e.g., sugar) and the liquid in which it dissolves is the solvent (e.g., water). Together they form a solution.
Q28. medium
A solution in which no more solute can dissolve at a given temperature is called:
- A A saturated solution
- B An unsaturated solution
- C A suspension
- D A mixture only
Answer: A — A saturated solution
A saturated solution holds the maximum amount of solute it can dissolve at that temperature. Adding more solute leaves it undissolved at the bottom.
Q30. medium
Which of these materials occurs NATURALLY?
- A Cotton and wood
- B Plastic
- C Nylon
- D Polyester
Answer: A — Cotton and wood
Cotton, wood, wool and silk are natural materials obtained from plants and animals. Plastic, nylon and polyester are man-made (synthetic) materials.
Q32. medium
Glass is used to make windows mainly because it is:
- A Transparent and hard
- B Soft and soluble
- C Opaque
- D A good conductor of electricity
Answer: A — Transparent and hard
Glass is chosen for windows because it is transparent (letting light in) and hard enough to keep out wind and rain. Properties decide the use of a material.
Q34. medium
Which of these is used to make raincoats because it does not let water pass through?
- A Plastic
- B Cotton cloth
- C Paper
- D Wool
Answer: A — Plastic
Plastic is waterproof, so it is used for raincoats and umbrellas. Cotton and paper absorb water, and wool soaks up moisture, so they are unsuitable.
Q36. medium
Which of these will FLOAT on water?
- A A piece of thermocol
- B An iron nail
- C A stone
- D A coin
Answer: A — A piece of thermocol
Thermocol is much less dense than water, so it floats. Iron nails, stones and coins are denser than water, so they sink.
Q38. medium
Which of these materials is SOLUBLE in water?
- A Common salt
- B Sawdust
- C Chalk powder
- D Sand
Answer: A — Common salt
Common salt dissolves completely in water, so it is soluble. Sawdust, chalk powder and sand do not dissolve and remain visible in the water.
Q40. medium
Materials are chosen for particular uses based on their:
- A Properties
- B Price only
- C Colour only
- D Age
Answer: A — Properties
The properties of a material - hardness, transparency, conductivity, solubility, density and flexibility - decide what it can be used for. Cost is also a factor, but properties come first.
Q42. medium
A material that can be bent easily without breaking is described as:
- A Flexible
- B Brittle
- C Hard
- D Lustrous
Answer: A — Flexible
Flexible materials such as rubber, wire and thin plastic can be bent without breaking. Brittle materials like glass and chalk break instead of bending.
Q44. medium
Which of these is a NON-METAL?
- A Sulphur
- B Iron
- C Copper
- D Aluminium
Answer: A — Sulphur
Sulphur is a non-metal - a yellow, brittle solid that does not conduct electricity. Iron, copper and aluminium are metals.
Q46. medium
Which of these would you use to make a hammer's head?
- A Iron - because it is hard and heavy
- B Rubber - because it is soft
- C Paper - because it is light
- D Glass - because it is transparent
Answer: A — Iron - because it is hard and heavy
A hammer head must be hard and heavy to deliver force without deforming, so iron or steel is used. Soft, light or brittle materials would be useless.
Q48. medium
Which method would you use to get back salt from salt water?
- A Evaporate the water
- B Filter the water
- C Add more water
- D Cool the water
Answer: A — Evaporate the water
Evaporating the water leaves the dissolved salt behind as a solid residue. Filtration does not work because dissolved salt passes through the filter paper.
Q50. medium
Which of these objects would be made from a TRANSPARENT material?
- A A window pane
- B A wooden door
- C A metal box
- D A cardboard carton
Answer: A — A window pane
A window pane is made of glass, a transparent material, so light can pass through and we can see outside. Wood, metal and cardboard are opaque.
Q52. medium
Which of these is TRUE about the appearance of materials?
- A Materials differ in lustre, texture, colour and hardness
- B All materials look exactly the same
- C Appearance never helps identify materials
- D Only colour matters
Answer: A — Materials differ in lustre, texture, colour and hardness
Materials differ in many observable ways - shine (lustre), roughness/smoothness (texture), colour and hardness. These help us identify and classify them.
Q54. medium
Which of these correctly describes the relation between objects and materials?
- A One material can make many objects, and one object can be made from many materials
- B Each material makes only one object
- C Objects have no materials
- D All objects use the same material
Answer: A — One material can make many objects, and one object can be made from many materials
Wood can make chairs, tables, doors and pencils (one material, many objects). A chair can be made of wood, plastic or metal (one object, many materials).
Q56. medium
Which property makes rubber suitable for making tyres?
- A It is flexible, tough and grips well
- B It is transparent
- C It conducts electricity
- D It dissolves in water
Answer: A — It is flexible, tough and grips well
Rubber is flexible, tough, elastic and provides good grip, making it ideal for tyres, which must absorb shocks and hold the road without breaking.
Q58. medium
Which of these is the best reason for classifying materials?
- A Similar materials can be studied and used together conveniently
- B It makes materials disappear
- C It changes their properties
- D It is required by law
Answer: A — Similar materials can be studied and used together conveniently
Classification groups materials by shared properties, so we can study them systematically, find them easily, and choose the right material for each purpose.
Q60. medium
Why are cooking vessels usually made of metal but their handles of plastic or wood?
- A Metals conduct heat well for cooking, while plastic and wood are poor conductors and stay cool to hold
- B Plastic is stronger than metal
- C Wood conducts heat better than metal
- D It is only for decoration
Answer: A — Metals conduct heat well for cooking, while plastic and wood are poor conductors and stay cool to hold
The vessel must transfer heat quickly to the food, so a good conductor like aluminium or steel is used. The handle must not transfer heat to the hand, so an insulator such as plastic or wood is chosen - a clear case of properties deciding uses.
Hard questions (28)
Q4. hard
Metals lose their shine and look dull after some time because of:
- A The action of air and moisture on their surface
- B Sunlight only
- C Their weight increasing
- D Being touched
Answer: A — The action of air and moisture on their surface
Air and moisture react with a metal's surface, forming a dull layer (like rust on iron or tarnish on silver). Rubbing or polishing removes this layer and restores the shine.
Q7. hard
Butter paper and frosted glass are examples of ______ materials.
- A Translucent
- B Transparent
- C Opaque
- D Lustrous
Answer: A — Translucent
Translucent materials let only some light through, so objects behind appear blurred and unclear. Butter paper, frosted glass and thin cloth are translucent.
Q9. hard
The HARDEST natural substance known is:
- A Diamond
- B Iron
- C Gold
- D Glass
Answer: A — Diamond
Diamond is the hardest natural substance. It is so hard that it can scratch every other material, which is why diamonds are used in cutting and drilling tools.
Q12. hard
Chalk powder mixed in water settles down after some time. This shows chalk is:
- A Insoluble in water
- B Soluble in water
- C A liquid
- D Transparent
Answer: A — Insoluble in water
Insoluble solids do not dissolve; their particles remain suspended and slowly settle to the bottom (sedimentation). Chalk powder behaves this way in water.
Q14. hard
Liquids that do NOT mix with each other are called:
- A Immiscible liquids
- B Miscible liquids
- C Soluble liquids
- D Solutions
Answer: A — Immiscible liquids
Immiscible liquids (like oil and water) form separate layers instead of mixing. Miscible liquids (like water and vinegar) mix completely to form a single liquid.
Q16. hard
A huge iron ship floats on water while a small iron nail sinks. This is because the ship:
- A Is shaped to displace a large amount of water, making its overall density less than water
- B Is made of a lighter metal
- C Is painted
- D Moves fast
Answer: A — Is shaped to displace a large amount of water, making its overall density less than water
A ship is hollow and shaped to push aside (displace) a large volume of water. This makes its average density less than that of water, so it floats - even though iron itself is denser than water.
Q18. hard
Why do we classify materials into groups?
- A It makes it easier to study them and predict their behaviour
- B To make them heavier
- C To change their colour
- D To destroy them
Answer: A — It makes it easier to study them and predict their behaviour
Classification helps us locate materials easily, study them systematically, and predict how a new material will behave if it belongs to a known group.
Q20. hard
The ability of a metal to be drawn into thin WIRES is called:
- A Ductility
- B Malleability
- C Lustre
- D Solubility
Answer: A — Ductility
Ductility is the property of being drawn into wires. Copper, aluminium, silver and gold are highly ductile, which is why they are used for wires.
Q21. hard
The ability of a metal to be beaten into thin SHEETS is called:
- A Malleability
- B Ductility
- C Hardness
- D Density
Answer: A — Malleability
Malleability is the property of being hammered into thin sheets. Aluminium foil and gold leaf show that these metals are highly malleable.
Q23. hard
Which metal is a LIQUID at room temperature?
- A Mercury
- B Iron
- C Copper
- D Gold
Answer: A — Mercury
Mercury is the only metal that is liquid at room temperature. This is why it was used in thermometers (though digital thermometers are safer today).
Q25. hard
Materials that do NOT allow heat or electricity to pass through them easily are called:
- A Insulators
- B Conductors
- C Metals
- D Solutions
Answer: A — Insulators
Insulators such as wood, plastic, rubber, glass and air resist the flow of heat and electricity. They are used for handles of utensils and coverings of wires.
Q27. hard
Water is often called the 'universal solvent' because it:
- A Dissolves a very large number of substances
- B Is found everywhere
- C Is transparent
- D Is tasteless
Answer: A — Dissolves a very large number of substances
Water can dissolve more substances than almost any other liquid, so it is called the universal solvent. This property makes it vital for life and for many chemical processes.
Q29. hard
More sugar can usually be dissolved in water if the water is:
- A Heated (warmer)
- B Cooled
- C Frozen
- D Kept in the dark
Answer: A — Heated (warmer)
Solubility of most solids increases with temperature. Hot water dissolves more sugar or salt than cold water, which is why sugar dissolves faster in hot tea.
Q31. hard
Materials made by humans in factories using chemicals are called:
- A Synthetic (man-made) materials
- B Natural materials
- C Elements
- D Minerals
Answer: A — Synthetic (man-made) materials
Synthetic materials such as plastic, nylon, polyester and rayon are manufactured by humans. They often have useful properties like strength, durability and low cost.
Q33. hard
Why are cooking pots made of metal but their handles of plastic or wood?
- A Metal conducts heat to cook food, while plastic/wood insulate so the handle stays cool
- B Metal is cheaper than plastic
- C Plastic conducts heat better
- D Wood cooks food faster
Answer: A — Metal conducts heat to cook food, while plastic/wood insulate so the handle stays cool
The metal body conducts heat quickly to cook the food, while the insulating handle does not conduct heat, letting us hold the pot safely. Materials are chosen for their properties.
Q35. hard
The property of a material that determines whether it will sink or float in water is its:
- A Density (compared to water)
- B Colour
- C Lustre
- D Smell
Answer: A — Density (compared to water)
Density is mass per unit volume. Materials less dense than water float; those denser than water sink. Wood floats, iron sinks.
Q37. hard
Which of these correctly matches a material with a key property?
- A Rubber - flexible; Diamond - very hard; Copper - good conductor
- B Rubber - hardest; Diamond - flexible
- C Copper - insulator; Rubber - conductor
- D Diamond - soft; Copper - transparent
Answer: A — Rubber - flexible; Diamond - very hard; Copper - good conductor
Rubber is flexible and elastic, diamond is the hardest natural substance, and copper is an excellent conductor of heat and electricity. Each property determines the material's uses.
Q39. hard
Gases can also dissolve in water. The gas dissolved in water that allows fish to breathe is:
- A Oxygen
- B Nitrogen
- C Carbon dioxide only
- D Hydrogen
Answer: A — Oxygen
Oxygen from the air dissolves in water, and aquatic animals like fish use this dissolved oxygen to breathe through their gills. Carbon dioxide also dissolves and is used by water plants.
Q41. hard
Why is a cricket ball NOT made of glass?
- A Glass is brittle and would shatter on impact
- B Glass is too soft
- C Glass is too light
- D Glass is opaque
Answer: A — Glass is brittle and would shatter on impact
Glass is brittle - it breaks easily when struck. A cricket ball must withstand hard impacts, so it is made of tough materials like leather and cork instead.
Q43. hard
Non-metals generally are:
- A Dull, brittle and poor conductors of heat and electricity
- B Shiny, malleable and good conductors
- C Always liquids
- D Always magnetic
Answer: A — Dull, brittle and poor conductors of heat and electricity
Non-metals such as sulphur, carbon and phosphorus are usually dull (non-lustrous), brittle in solid form, and poor conductors - the opposite of most metals. (Graphite is an exception that conducts electricity.)
Q45. hard
Which property of metals makes them ring when struck (used in bells)?
- A Sonority
- B Solubility
- C Transparency
- D Density
Answer: A — Sonority
Sonority is the property of producing a ringing sound when struck. Metals are sonorous, which is why bells, gongs and cymbals are made of metal.
Q47. hard
When salt is dissolved in water, the salt:
- A Is still present in the water though it cannot be seen
- B Disappears completely and is destroyed
- C Turns into water
- D Becomes a gas
Answer: A — Is still present in the water though it cannot be seen
Dissolving does not destroy the solute. The salt particles spread out among the water particles and become invisible, but they are still there - you can taste the salt, and evaporating the water leaves it behind.
Q49. hard
Which of these mixtures would you describe as a SOLUTION?
- A Sugar completely dissolved in water
- B Sand mixed with water
- C Oil floating on water
- D Chalk powder in water
Answer: A — Sugar completely dissolved in water
A solution is a uniform (homogeneous) mixture in which the solute is completely dissolved and cannot be seen separately. Sand, oil and chalk in water form non-uniform mixtures.
Q51. hard
Aluminium is used to make cooking foil because it is:
- A Highly malleable and a good conductor of heat
- B Transparent
- C Soluble in water
- D Very heavy
Answer: A — Highly malleable and a good conductor of heat
Aluminium can be beaten into extremely thin sheets (malleability) and conducts heat well, making it ideal for cooking foil and food packaging. It is also light and resists corrosion.
Q53. hard
A material that is hard, lustrous, malleable and conducts electricity is most likely a:
- A Metal
- B Non-metal
- C Gas
- D Plastic
Answer: A — Metal
Hardness, lustre, malleability and electrical conductivity together are the typical properties of metals. Non-metals, gases and plastics do not show all these together.
Q55. hard
Oil floats on water because oil:
- A Is less dense than water and immiscible with it
- B Dissolves in water
- C Is heavier than water
- D Is a solid
Answer: A — Is less dense than water and immiscible with it
Oil is less dense than water, so it rises to the top, and it is immiscible (does not mix), so it forms a separate layer rather than dissolving.
Q57. hard
Which of these statements about solubility is CORRECT?
- A Different substances have different solubilities in the same solvent
- B All substances dissolve equally in water
- C Nothing dissolves in water
- D Solubility never changes with temperature
Answer: A — Different substances have different solubilities in the same solvent
Different substances dissolve to different extents in the same solvent - salt and sugar dissolve well in water, chalk does not. Solubility also usually increases with temperature for solids.
Q59. hard
Which overall statement about materials is CORRECT?
- A Materials differ in properties like lustre, hardness, solubility, transparency and density, and these decide their uses
- B All materials have identical properties
- C Properties have nothing to do with uses
- D Only metals have properties
Answer: A — Materials differ in properties like lustre, hardness, solubility, transparency and density, and these decide their uses
Every material has a set of properties - appearance, hardness, solubility, transparency, density, conductivity and flexibility. Understanding these properties lets us classify materials and choose the right one for each job.