Grade 9 Chemistry, Lesson 3 - Physical and Chemical Properties and Changes
Summary
TLDRThis chemistry lesson explores the distinction between physical and chemical properties and changes. Physical properties, such as state of matter, color, and density, can be measured without altering a substance. Chemical properties, however, require a reaction to be observed. The video clarifies this by contrasting physical changes, like cutting bread or turning on a light, with chemical changes, such as baking bread or frying an egg, which result in new substances. It also discusses how to identify chemical changes through color changes, heat production, and irreversibility.
Takeaways
- 🧪 Physical properties are characteristics of substances that can be measured without changing the substance's identity, such as state of matter, color, density, and hardness.
- 🔨 Hardness is the resistance of a solid to being scratched or dented, as illustrated by the scratches on a canoe from rocks.
- 🛠 Malleability refers to how easily a substance can be hammered or bent into different shapes, with metals and Play-Doh being examples of malleable substances.
- 🧵 Ductility is the ability of a substance to be pulled into wires without breaking, as demonstrated by stretching aluminum.
- 💧 Solubility is a physical property that describes a substance's ability to dissolve in a solvent, like salt dissolving in water.
- 🍯 Viscosity is a measure of a liquid's resistance to flow, with honey being an example of a highly viscous substance.
- 🔥 Chemical properties describe a substance's potential to react chemically with other substances to form new compounds, and they can only be observed through chemical reactions.
- 🔥 Combustibility and flammability are chemical properties that indicate a substance's ability to react quickly with oxygen, producing heat and light, such as catching on fire.
- 🌡 Acidic or basic properties are also chemical properties that define how a substance reacts with other chemicals.
- 🥚 Chemical changes involve the creation of a new substance, such as the reaction of hydrogen and oxygen to form water (H2O).
- 🧊 Physical changes do not result in the creation of a new substance, but may involve a change in state, like water turning into ice.
Q & A
What are physical properties?
-Physical properties are characteristics of substances that can be measured or observed without changing the composition of the substance. Examples include state of matter, boiling and melting points, color, luster, density, hardness, malleability, ductility, and solubility.
What is the difference between hardness and malleability?
-Hardness is the resistance of a solid to being scratched or dented, while malleability describes how easily a substance can be hammered or bent into different shapes.
Can you give an example of a physical property that demonstrates ductility?
-An example of ductility is a tube of aluminum, which can be stretched out into a longer, thinner version without snapping.
What is solubility in the context of physical properties?
-Solubility is the ability of a substance to dissolve in a solvent, such as salt dissolving in water.
How does viscosity relate to the flow of a liquid?
-Viscosity of a substance describes how quickly it flows in its liquid form. A higher viscosity indicates a slower flow, like honey pouring slowly over a plate.
What are chemical properties?
-Chemical properties describe the ability of a substance to chemically react with another substance to produce a new chemical. They can only be observed through a chemical reaction.
What are some examples of chemical properties?
-Examples of chemical properties include combustibility (ability to react with oxygen and produce heat and light) and acidity or basicity, which describe reactions with other chemicals.
How can you distinguish between a chemical change and a physical change?
-A chemical change involves the creation of a new substance, while a physical change involves a change in state or appearance without the formation of a new substance.
What are some indicators that a chemical change has occurred?
-Indicators of a chemical change include the appearance of a new color, the release of heat or light, the formation of gas bubbles, the creation of a precipitate when two liquids are mixed, and the difficulty of reversing the change.
Can you provide an example of a chemical change from the script?
-An example of a chemical change from the script is baking a loaf of bread, which is hard to reverse and involves a color change.
What is the difference between turning on a light bulb and frying an egg in terms of physical and chemical changes?
-Turning on a light bulb is a physical change because it can be easily reversed and does not involve the creation of a new substance, while frying an egg is a chemical change due to the color change and the difficulty of reversing the process.
Outlines
🔬 Physical and Chemical Properties and Changes
In this segment, Mr. Lehan introduces the concepts of physical and chemical properties and changes in the context of grade N chemistry. Physical properties are measurable characteristics like state of matter, boiling and melting points, color, luster, density, hardness, malleability, ductility, solubility, and viscosity. These properties can be observed without changing the substance's chemical identity. Chemical properties, on the other hand, describe how substances react with others to form new substances, and they can only be observed through chemical reactions. Examples include combustibility, acidity, and basicity. The distinction between physical and chemical changes is also discussed, with chemical changes involving the formation of new substances, often indicated by color change, heat or light emission, gas formation, or precipitate formation, and being difficult to reverse.
🔍 Distinguishing Between Physical and Chemical Changes
This paragraph delves into differentiating between physical and chemical changes through various examples. Baking bread is identified as a chemical change due to its irreversibility and color change, while cutting bread is a physical change as it only alters the shape without creating new substances. Putting peanut butter on bread and mixing red and yellow paint to make orange are also physical changes, as they involve combining existing substances without altering their molecular structures. Setting bread on fire and frying an egg are classified as chemical changes due to the production of light and heat, color change, and the difficulty of reversing the process. The segment also touches on the tricky case of turning on a light bulb, which, despite producing light and heat, is a physical change because it is easily reversible.
Mindmap
Keywords
💡Physical properties
💡Chemical properties
💡Chemical changes
💡Physical changes
💡Hardness
💡Malleability
💡Ductility
💡Solubility
💡Viscosity
💡Combustibility
💡Acidic and Basic
Highlights
Introduction to physical and chemical properties and changes in grade N chemistry.
Physical properties are characteristics of substances that can be measured without changing the substance.
Examples of physical properties include state of matter, boiling and melting points, color, luster, density, hardness, malleability, ductility, and solubility.
Hardness is the resistance of a solid to being scratched or dented, illustrated with a canoe with scratches.
Malleability is the ability of a substance to be hammered or bent into different shapes, as shown with hot metal being hammered.
Ductility is the ability of a substance to be pulled into wires without snapping, using aluminum as an example.
Solubility is the ability of a substance to dissolve in a solvent, demonstrated with salt dissolving in water.
Viscosity describes how quickly a liquid flows, using honey pouring as an example of a viscous substance.
Chemical properties describe a substance's ability to chemically react with another to produce a new chemical.
Chemical properties require a chemical reaction to be observed, such as combustibility or acidity.
Chemical changes involve the creation of a new chemical substance, like hydrogen and oxygen reacting to form water.
Physical changes do not create new substances but involve changes in state or form, such as water freezing.
Clues of a chemical change include new color, heat or light production, gas bubbles, precipitate formation, and difficulty in reversing the change.
Baking bread is a chemical change due to its irreversibility and color change.
Cutting bread is a physical change as it only alters the shape without creating new substances.
Putting peanut butter on bread is a physical change with no new molecules being created.
Setting bread on fire is a chemical change characterized by light and heat production and color change.
Mixing red and yellow paint to make orange is a physical change despite the color change.
Turning on a light bulb is a physical change, not a chemical change, despite producing light and heat.
Frying an egg is a chemical change due to color change and irreversibility, characteristic of cooking.
Upcoming video on the history of atomic theory to be released.
Transcripts
all right welcome to Mr lehan teaches
you stuff this is grade n chemistry
lesson three physical and chemical
properties and
changes so physical properties describe
the characteristics of substances that
we can measure um and I'm just going to
go through several examples of physical
properties now so you get an idea of
what they are and if they require a
little bit more explanation I'll give a
quick definition of what they are so the
state of matter at room temperature is a
physical property so whether something's
a solid a liquid or a
gas other physical properties include
the boiling and melting points the color
the shininess or the luster and the
density of an object these are all
physical
properties another one is hardness and
hardness is the resistance of a solid to
being scratched or
dented um this is a picture here of my
canoe it's got a bunch of scratches on
the bottom and that's because my canoe
was not as hard as the rocks that I ran
into
so that's what hardness is uh
malleability describes how easily a
substance can be hammered or bent into
different
shapes so here we have a picture of a
piece of very hot metal being hammered
out uh most metals are fairly malleable
other things that would be malleable
would be uh Playdoh you can very easily
Hammer Play-Doh into different
shapes ductility that might be another
one you're not too familiar with this is
how easily a substance can be pulled out
into wires without snapping so if we
have a little you know tube of aluminum
or something here when you pull on
either end it'll get stretched out
without snapping into a longer thinner
version of itself that's
ductility solubility is the ability of a
substance to dissolve in a solvent so
for instance salt is dissolving in water
here so the salt is soluble in the water
that's a physical
property viscosity of a substance
describes how quickly it flows in its
liquid form so here we have a picture of
some honey being poured onto a plate and
you can see that the honey is sort of
folding over on itself and that's
because it's very viscous so it flows
very
slowly all right now we're going to look
at chemical properties so chemical
properties describe the ability of a
substance to chemically react with
another substance to produce a new
chemical so for chemical properties it's
not something where you can measure it
without reacting it with something
to see a chemical property you have to
see a chemical reaction take
place so chemical properties can only be
seen when a chemical reaction happens
you can't just look at something and say
wow that looks basic or that looks
acidic there's going to have to be some
sort of chemical reaction for you to you
to
tell so some examples of chemical
properties uh if a substance is
combustible or flammable that means it
will react quickly with oxygen and
produce heat light it'll catch on
fire uh if a substance is acidic or
basic that also describes how it reacts
with other chemicals so that's a
chemical
property okay so now we're going to look
at chemical and physical changes so not
properties but changes uh when a new
chemical substance is created it is a
chemical change so for example if we
have two hydrogen react with one oxygen
to make H2O or water that's going to be
a chemical change because a new
substance a new chemical substance the
water has been
created if on the other hand a chemical
is not changed right the chemicals don't
change there's nothing new it's a
physical change so if we have liquid
water turning into solid water or ice
this is a physical change things did
change it changeed State uh but the
chemicals are all the same so it's not a
chemical change
so here are several clues that a new
chemical has been
created a new color
appears heat or light are given off
bubbles of gas are
formed a solid material called a
precipitate appears when two liquids are
mixed and the change is difficult to
reverse so if you see any or all of
those it's usually a good clue that a
chemical reaction has taken place a
chemical change has taken
place all right so now we're going to go
through several different scenarios and
decide whether they are physical or
chemical changes so first off baking a
loaf of bread is this physical or
chemical this one's chemical it's very
hard to reverse you can't revert the
bread back into
dough uh and also a there's also a color
change right it's uh darker brown when
it's
baked what about cutting a slice of
bread this one is physical so although
it's hard to reverse you can't
unsliced uh the chemicals that you end
up with at the end are the same
chemicals that you started with right
nothing new has been created we've just
change the shape of the
bread putting peanut butter on
bread uh well this one the color changes
I guess cuz there's peanut butter on
it but you're still starting off with
bread and peanut butter and you end up
with bread and peanut butter so there's
really no change here there's no new
mole molecules being
created so this one is a physical
change what about setting the bread on
fire so we're producing light and heat
uh there will be a color change in the
bread it's getting sort of
blackened this is a chemical change you
will not be able to unfire this
bread mixing red and yellow paint to get
orange so here we definitely have a
color change and that was one of our one
of our clues that a chemical change has
happened but in this case this is a
physical change so we're really just
mixing all the little particles of paint
together to make an orange color but the
molecules that make up the paint have
not really changed they're all still the
same paint molecules if you
will all right turning on a light bulb
uh this one's a little tricky as well
because it produces light and heat which
is another one of our clues that a
chemical change has taken place but this
is very easy to reverse you just turn
the light switch back off and it goes
off so this is not a chemical change
this is just a physical
change and frying an egg this is our
last example frying an egg it definitely
changes color it's very difficult to
reverse basic well you can't reverse it
you can't unfry an egg
uh basically anytime you cook anything
or you bake
anything you are making a chemical
change so frying an egg is a chemical
change so that's it for this video uh
tune in for next video the history of
atomic theory
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