CLASS 6 SCIENCE · CHAPTER 6 · STUDY NOTES
Materials Around Us
Connect each material’s properties with its use, then distinguish mass, volume and matter.
01 / EXPLORE & UNDERSTAND
An object is not the same as its material
A chair is an object. Wood, plastic and metal are possible materials for making it.
1. One object, several possible materials
A tumbler can be made of glass, steel or suitable plastic. The object’s job can stay similar while its material changes. A pen can contain several materials at once: plastic, metal and ink.
2. One material, several objects
Wood can form a chair, a door or a pencil body. Naming the material alone does not identify the object. Ask both “What is it?” and “What is it made of?”
Your turn
Question
Why is “glass” an incomplete answer to “Which object is on the table?”
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02 / EXPLORE & UNDERSTAND
Choose properties for a purpose
The best material depends on what the object must do.
1. Start with the job
A water container must hold water without leaking. Ordinary loose cloth is unsuitable by itself. A cooking vessel must cope with heating. One attractive property, such as colour, cannot decide every use.
2. Compare fairly
Sports balls use different materials for different jobs. To compare bounce, keep the drop height and surface the same. Record the result instead of deciding from the ball’s appearance. In a cupboard, grouping by use may be more helpful than grouping by colour.
Your turn
Question
Two balls are dropped from different heights. Can their bounce heights alone fairly compare the materials?
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03 / EXPLORE & UNDERSTAND
Shiny does not always mean metal
Look at the surface, then ask what else could explain its shine.
1. Observe before identifying
Many freshly exposed metal surfaces are shiny. Paper and unpolished wood usually look dull. Record the appearance as an observation rather than immediately naming the material.
2. Check the coating and the age of the surface
A plastic coating or polish can make a non-metal object shiny. Air and moisture can make a metal surface dull. Shine is useful evidence, but cannot prove by itself that an object is metal.
Your turn
Question
A shiny birthday ribbon is called metal only because it shines. What is wrong with the reasoning?
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04 / EXPLORE & UNDERSTAND
Hard and soft are comparisons
Describe what happened when you tested the material, and name the comparison.
1. Compare the same action
A sponge compresses easily under gentle pressure; an iron piece does not. Rubber can be harder than sponge and softer than iron. “Hard” is more useful when the compared materials are clear.
2. Do not confuse different properties
Hardness, flexibility and brittleness are not the same. Glass can be hard yet break easily when struck. For a classroom comparison, use teacher-provided safe samples; do not scratch furniture or handle broken glass.
Your turn
Question
Does a hard glass cup have to be unbreakable? Explain.
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05 / EXPLORE & UNDERSTAND
Can you see through it clearly?
Compare the view through the material, not just the material’s colour.
Compare three views through materials
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1. Use the same object behind each sample
Through clean clear glass you can see a detailed object. Through frosted glass its outline looks blurred. A wooden board blocks the view. Compare the same object in similar lighting.
2. Choose the actual form of the material
Not every kind of glass gives the same view: clear glass and frosted glass differ. Muddy water can hide objects that clean water lets you see. Describe the sample you tested, not every possible form of the material.
Your turn
Question
Which is useful when a window should admit light but blur the view: clear or frosted glass? Why?
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06 / EXPLORE & UNDERSTAND
Dissolved does not mean destroyed
Small amounts of salt or sugar can seem to disappear when stirred into water. They are still present.
Visible particles versus a clear solution
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1. Compare after stirring and waiting
Salt forms a solution when enough water is present. Sand stays as visible particles and can settle. Stirring can temporarily spread an insoluble powder through water without making it dissolve. Never taste classroom mixtures to identify them.
2. Liquids and gases can also mix with water
Vinegar mixes with water; oil tends to form a separate layer after standing. Oxygen gas dissolves in water and helps aquatic organisms breathe. Clear-looking water is not automatically safe drinking water.
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Question
A cloudy mixture becomes clear at the top while powder settles below. Did all the powder dissolve?
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07 / EXPLORE & UNDERSTAND
Compare mass with a balance
Two equally full containers need not have the same mass.
Read mass with a balance
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1. Control the container
Use identical empty cups when comparing materials. Otherwise, a heavier cup could affect the result. Weigh the empty container or subtract its mass if you need the material’s mass alone.
2. Write the unit clearly
The SI unit of mass is kilogram, kg. A classroom balance may show grams, g. Write 250 g or 2 kg with a space and without a plural s. Mass and the force called weight are related but are not the same physical quantity.
Your turn
Question
Cup plus rice is 180 g. The empty cup is 30 g. What is the rice’s mass?
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08 / EXPLORE & UNDERSTAND
Volume means occupied space
A container’s capacity and the volume inside it are different ideas.
Equal containers, different water volumes
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1. Compare identical containers first
If two identical upright tumblers contain the same liquid, the higher level means more liquid volume. The containers may have equal capacity even when one is only half full.
2. Shape can mislead the eye
A tall narrow vessel can hold the same amount as a short wide one. Compare marked volumes, not height alone. Common liquid units are L and mL; 1 L = 1000 mL. The SI unit of volume is the cubic metre, m³.
Your turn
Question
A 1 L bottle contains 300 mL. State its capacity and its water volume.
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09 / EXPLORE & UNDERSTAND
Air is matter too
Matter includes more than the solid objects you can hold.
1. Use both properties
Water and a stone have mass and occupy space. Air does too, even though you normally cannot see it. A balloon expands when air goes in because the air occupies space; measurements are needed to demonstrate its mass.
2. Bring the properties together
Classifying by shine, hardness, transparency or solubility answers different questions. One sample belongs to several groups. The chapter also describes historical classifications, including paired qualities such as hard and soft; these show that people have long compared material properties.
Your turn
Question
Can the same sample be transparent and insoluble in water? Explain the two tests.
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Sign inNew here? Sign up freeCHAPTER RECAP
Take these ideas with you
- Name the object and its material separately.
- A useful material has properties that suit its purpose.
- Shine alone cannot prove a material is metal.
- Transparent, translucent and opaque describe how clearly we see through a sample.
- Dissolving spreads material through water; it does not destroy the material.
- Mass and occupied space are different properties; all matter has both.
Use your understanding in a new situation
Question
A designer wants a storage box that shows what is inside. Which property matters, and what other practical property should also be checked?
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Two differently shaped bottles each contain 500 mL. One has a higher water level. Which has more water?
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Sign inNew here? Sign up freeNCERT · Chapter source PDF, pages 15, 16, 17, 18 · Original Learnijoy explanations and practice.