Class 9 Exam > Class 9 Videos > Changes in States of Matter - Is Matter Around us Pure?
Changes in States of Matter - Is Matter Around us Pure? Video Lecture - Class 9
FAQs on Changes in States of Matter - Is Matter Around us Pure? Video Lecture - Class 9
| 1. What are the different states of matter? |  |
Ans. The different states of matter are solid, liquid, and gas. In solids, particles are closely packed together and have a fixed shape and volume. Liquids have particles that are close together but can move around, giving them a definite volume but no fixed shape. Gases have particles that are far apart and can move freely, occupying the entire space available to them.
| 2. How does matter change its state? | |
Ans. Matter can change its state through heating or cooling. When a solid is heated, it gains energy and its particles vibrate faster, eventually breaking the forces holding them in place and turning into a liquid. Further heating turns the liquid into a gas by increasing the energy of the particles to the point where they can overcome the forces of attraction between them. Cooling, on the other hand, removes energy from matter, causing the particles to slow down and eventually form a solid.
| 3. What is the process of condensation? | |
Ans. Condensation is the process by which a gas changes into a liquid state. It occurs when the temperature of a gas is lowered, causing the particles to lose energy and slow down. As a result, the particles come closer together and form bonds, leading to the formation of liquid droplets. This process is commonly observed when steam condenses into water droplets on a cold surface, such as a mirror or a window.
| 4. Can matter exist in multiple states at the same time? | |
Ans. Yes, matter can exist in multiple states at the same time under certain conditions. For example, during the process of melting, both solid and liquid states of matter can coexist. At the melting point, the solid begins to change into a liquid, but some solid particles may still remain. This coexistence of states is also observed during boiling, where both liquid and gas phases can be present.
| 5. What is sublimation and give an example? | |
Ans. Sublimation is the process in which a substance directly changes from a solid to a gaseous state without passing through the liquid state. This occurs when the substance is heated and its particles gain enough energy to break the forces holding them together as a solid. An example of sublimation is the conversion of dry ice (solid carbon dioxide) into carbon dioxide gas without melting in between.
Text Transcript from Video
there are other kinds of physical
changes that occur with water and other
substances when water boils it turns
into a gas water vapor but while
evaporation occurs only at the surface
of a liquid boiling causes a liquid to
turn into a gas below the surface the
bubbles in this boiling water are made
up of water vapor when a liquid boils
the molecules that make up the liquid
are pulled apart to become a gas boiling
is different from evaporation in another
way while evaporation occurs at
different temperatures each kind of
liquid boils at a specific temperature
called its boiling point for water the
boiling point at sea level is around 100
degrees Celsius or 212 degrees
Fahrenheit matter can change from one
phase to another in still other ways as
we saw earlier a solid can change into a
liquid when it's heated the temperature
at which this change happens is called
the solids melting point the melting
points of different kinds of rock are
very high on average about 1,200 degrees
Celsius the melting point of ice is much
lower at sea level ice melts at just
above zero degrees Celsius or 32 degrees
Fahrenheit zero degrees Celsius is also
the freezing point of water because at
sea level when the temperature goes
below this level water will turn into
solid ice most liquids take up less
space when they freeze because their
molecules are bound more tightly
together when they turn into solids but
water is an exception when water freezes
the ice that forms has more volume here
for example 150 milliliters of water
turned into about 160 milliliters of ice
the reason ice has greater volume is
that when water freezes its molecules
lock together to form rigid
hollow rings these hollow rings take up
more space than the water molecules did
when they were liquid there are other
unusual exceptions to how matter changes
from one phase to another dry ice for
instance is the solid phase of carbon
dioxide it is so cold that it causes
water vapor in the air to condense into
a fine white mist but when it is exposed
to warm air dry ice doesn't melt rather
than changing into a liquid the solid
carbon dioxide changes directly into an
invisible gas when matter changes
directly from a solid to a gas or from a
gas to a solid such a change is called
sublimation
changes that occur with water and other
substances when water boils it turns
into a gas water vapor but while
evaporation occurs only at the surface
of a liquid boiling causes a liquid to
turn into a gas below the surface the
bubbles in this boiling water are made
up of water vapor when a liquid boils
the molecules that make up the liquid
are pulled apart to become a gas boiling
is different from evaporation in another
way while evaporation occurs at
different temperatures each kind of
liquid boils at a specific temperature
called its boiling point for water the
boiling point at sea level is around 100
degrees Celsius or 212 degrees
Fahrenheit matter can change from one
phase to another in still other ways as
we saw earlier a solid can change into a
liquid when it's heated the temperature
at which this change happens is called
the solids melting point the melting
points of different kinds of rock are
very high on average about 1,200 degrees
Celsius the melting point of ice is much
lower at sea level ice melts at just
above zero degrees Celsius or 32 degrees
Fahrenheit zero degrees Celsius is also
the freezing point of water because at
sea level when the temperature goes
below this level water will turn into
solid ice most liquids take up less
space when they freeze because their
molecules are bound more tightly
together when they turn into solids but
water is an exception when water freezes
the ice that forms has more volume here
for example 150 milliliters of water
turned into about 160 milliliters of ice
the reason ice has greater volume is
that when water freezes its molecules
lock together to form rigid
hollow rings these hollow rings take up
more space than the water molecules did
when they were liquid there are other
unusual exceptions to how matter changes
from one phase to another dry ice for
instance is the solid phase of carbon
dioxide it is so cold that it causes
water vapor in the air to condense into
a fine white mist but when it is exposed
to warm air dry ice doesn't melt rather
than changing into a liquid the solid
carbon dioxide changes directly into an
invisible gas when matter changes
directly from a solid to a gas or from a
gas to a solid such a change is called
sublimation
About this Video
Sep 03, 2025
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