Metals and Nonmetals Class 8 Science - Physical Properties of Metals and Nonmetals
Summary
TLDRThis script explores the physical properties that differentiate metals from non-metals. Metals exhibit a metallic luster, are hard, malleable, ductile, and sonorous, with excellent heat and electricity conductivityβunlike non-metals, which are soft, dull, and poor conductors. Notably, exceptions like sodium and potassium are soft metals, and mercury is a liquid metal, while diamond, a non-metal, is the hardest substance. The video emphasizes that both physical and chemical properties are crucial for accurate classification.
Takeaways
- π Metals exhibit a shining surface known as metallic luster, while non-metals are typically dull and lack this property.
- π¨ Metals are generally hard and difficult to cut with a knife, unlike non-metals which are soft and easy to cut.
- π¨ Malleability is a property of metals where they can be beaten into thin sheets without breaking, unlike non-metals which tend to break.
- 𧡠Ductility is the ability of metals to be drawn into thin wires, a property not shown by non-metals.
- π Sonority is the property of producing a ringing sound when struck, which is characteristic of metals but not non-metals.
- π₯ Metals conduct heat efficiently, as demonstrated by the heat transfer through an iron rod, a property not found in non-metals.
- β‘ Metals are good conductors of electricity, which can be tested by observing if a bulb lights up when connected in a circuit, whereas non-metals are poor conductors.
- π‘ There are exceptions to the general properties of metals and non-metals, such as sodium and potassium being soft and easily cut like non-metals.
- π§ Mercury is the only metal that is liquid at room temperature, unlike other metals which are solid.
- π Diamond, a non-metal, is the hardest known substance, which contradicts the general softness of non-metals.
- β οΈ Physical properties alone are not sufficient to classify a substance as a metal or non-metal; chemical properties must also be considered.
Q & A
What is the term used to describe the shining surface of pure metals?
-The term used to describe the shining surface of pure metals is 'metallic luster'.
How do the physical properties of metals differ from those of non-metals in terms of luster?
-Metals exhibit a shining surface known as metallic luster, while non-metals are dull and do not have luster.
Why is it difficult to cut iron with a knife?
-It is difficult to cut iron with a knife because metals are hard, which is a physical property of metals.
What property of metals allows them to change shape when beaten with a hammer?
-The property that allows metals to change shape when beaten is called 'malleability'.
What is the term for the ability of metals to form thin wires?
-The ability of metals to form thin wires is known as 'ductility'.
Why do metals produce a ringing sound when struck by a hard substance?
-Metals produce a ringing sound when struck due to a property called 'sonority'.
How do metals differ from non-metals in terms of heat conduction?
-Metals conduct heat, whereas non-metals do not conduct heat, making metals suitable for use in cookware handles.
What property makes metals suitable for use in electrical wiring?
-Metals are good conductors of electricity, which makes them suitable for use in electrical wiring.
Are there any exceptions to the general physical properties of metals and non-metals mentioned in the script?
-Yes, there are exceptions. For example, sodium and potassium are soft metals that can be cut with a knife, and mercury is a metal that is liquid at room temperature. Iodine is a non-metal that is lustrous, and diamond, although a non-metal, is the hardest known substance.
Why is it insufficient to classify substances as metals or non-metals based solely on their physical properties?
-It is insufficient to classify substances as metals or non-metals based solely on physical properties because there are exceptions to these properties, and a comprehensive classification requires the study of chemical properties as well.
What did the script suggest for further understanding of elements?
-The script suggests that for a deeper understanding of elements, one should study their chemical properties in addition to their physical properties, which will be covered in upcoming videos.
Outlines
π Physical Properties of Metals and Non-Metals
This paragraph delves into the physical distinctions between metals and non-metals, highlighting key attributes such as luster, where metals exhibit a shiny surface compared to the dull appearance of non-metals. Hardness is also discussed, with metals being hard and non-metals being soft, as demonstrated through the difficulty of cutting iron versus the ease of cutting rubber. The paragraph further explains the malleability of metals, their ability to be hammered into thin sheets without breaking, unlike non-metals. Ductility, another metal property, allows metals to be drawn into thin wires, a feat non-metals cannot achieve. Sonority, or the ringing sound when struck, is a characteristic of metals but not non-metals. The paragraph also covers the conduction of heat and electricity, with metals being efficient conductors, unlike non-metals. Exceptions to these general properties are noted, such as soft metals like sodium and potassium, and the lustrous appearance of non-metals like iodine and the hardness of diamond.
π Exceptions and the Importance of Chemical Properties
The second paragraph acknowledges that while physical properties are a starting point for classifying elements, they are not definitive. It points out exceptions to the general properties of metals and non-metals, such as mercury being a liquid metal and iodine being a lustrous non-metal. The paragraph emphasizes that to accurately classify substances, one must also consider their chemical properties, which will be explored in future videos. This sets the stage for a deeper understanding of elements beyond their physical appearance and behavior.
Mindmap
Keywords
π‘Luster
π‘Hardness
π‘Malleability
π‘Ductility
π‘Sonority
π‘Conduction of Heat
π‘Conduction of Electricity
π‘Exceptions
π‘Physical Properties
π‘Chemical Properties
Highlights
Scientists group elements based on their physical and chemical properties.
Metals exhibit a shining surface known as metallic luster, unlike non-metals which are dull.
Metals are hard, making it difficult to cut them with a knife, unlike the softness of non-metals.
Malleability is a property of metals, allowing them to change shape when beaten, unlike non-metals that break.
Ductility is the ability of metals to form thin wires, a property not shown by non-metals.
Sonority is the property of metals to produce a ringing sound when struck, which non-metals lack.
Metals conduct heat, as demonstrated by the temperature rise at the other end of a heated iron rod.
Non-metals do not conduct heat, making them unsuitable for use as handles for cookware.
Metals are good conductors of electricity, verified by the lighting of a bulb in an electrical circuit.
Non-metals are poor conductors of electricity, as shown by the lack of bulb lighting with non-metallic materials.
Sodium and potassium are exceptions to the hardness rule of metals, being soft and easily cleaved.
All metals are solid except for mercury, which is a liquid at room temperature.
Iodine is a non-metal that is lustrous, challenging the traditional classification based on physical properties alone.
Diamond, a non-metal, is the hardest known substance, further complicating the classification of materials.
Physical properties alone are insufficient for classifying substances as metals or non-metals; chemical properties must also be considered.
Further study of chemical properties is necessary for accurate classification, to be covered in upcoming videos.
The video concludes by thanking viewers for watching and encouraging them to learn more about chemical properties in future content.
Transcripts
physical properties of metals and
non-metals
when scientists were discovering
elements
they felt the need to group these
elements
it can be done by grouping these
elements by studying their physical
and chemical properties
let's try to understand some physical
properties of metals and non-metals
luster
all metals in the pure state have a
shining surface
this property is called
metallic luster
non-metals on the other hand
are dull
therefore
they do not have luster
hardness
try to cut iron with knife
isn't it very difficult
why
because
metals are hard
now try to cut a rubber with knife
it must be very easy
thus non-metals are soft
malleability
let's perform an activity
take iron nail
gold piece
piece of thick aluminum wire pencil lid
beat each of them with a hammer
what do you observe
iron nail and aluminum wire
change their shape
but coal piece and pencil lead break
into pieces
hideaway beat
greater is the change of shape
thus
metals if beaten
change their shape and forms thin sheet
on beating
this property is called
malleability
non-metals break into pieces like we
have seen in activity
ductility
another interesting property of metals
is the ability to form thin wires
it is called ductility
with this property
you can see wires of aluminium
copper
iron
non-metals do not show this property
and breaks if we try to form wires
sonority
the property of producing ringing sound
when a substance is struck by a hard
substance
is called
sonority
metals are sonarus
but non-metals are not
conduction of heat
if one end of iron rod is heated
then we can feel rise in temperature at
other end also
this means that
metals
conduct heat
non-metals does not conduct heat
if non-metals would have been conducting
heat will it be possible to use them as
handles for cookers and pans
no
conduction of electricity
let's perform another activity
connect circuit as shown
check
if the bulb lights or not
repeat the same for other materials
observation
material
and conductivity
iron nail
is good conductor
sulfur
is bad conductor
coal piece
is bad conductor
copper wire
is good conductor
from this activity you can verify that
metals
are good conductor of electricity
but non-metals
are bad conductor of electricity
exceptions
sodium
and potassium
are soft
and can be easily cleaved
that is
cut
to form plain surface
by knife
however
these belongs to metals
similarly
all metals are solid
except mercury
which exist in liquid form iodine is
non-metal
but it is lustrous
diamond is hardest substance which is a
non-metal
what this means is that
we cannot classify substance as metals
or non-metals
only on the physical properties
to classify
we have to study the chemical properties
as well
we will learn about them in upcoming
videos thanks for watching
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