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Unit One: Matter and Its Construction

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by

Ahmed Hussein

on 19 August 2016

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Transcript of Unit One: Matter and Its Construction

Life application
I. Water is not used in
extinguishing
petrol fires because petroleum oil floats over water surface

2. Balloons filled with
hydrogen or helium
rise upwards carrying flags during festivals since their densities are lighter than that of air..

Matter
Matter
is surrounding us everywhere.
It is everything that has mass and volume (occupies space.)

Substances
differ in some of their characteristics such as color, taste and smell.
A substance may differ than
another
in its
colour
, its
taste
, its
smell
or even in
all of these characteristics
For example
colour
enables us distinguishing among iron, gold and silver.
Also the taste enables us distinguishing between sugar and table salt, and at last,
smell
enables us distinguishing between
perfume
and
vinegar
.

There are also some other substances have no colour,
no smell or no taste.
Such as
water
and
oxygen
gas.

These substances can be distinguished from each others by other different characteristics.
Example
Example on finding a liquid density through an experiment, the following results were recorded:
Mass of an empty glass beaker = 75 g
Mass of the beaker containing liquid = 135 g
Volume of the liquid measured by a graduated cylinder = 100 cm³
50 we can calculate the liquid density as follows:
Mass of liquid = I35 - 75 = 60 g.


Density
Density
: it is the mass of unit volume of a substance (mass of one cubic centimeter 1 cm³).
So density is related to an object mass and to its volume as well:

Unit One: Matter and It's Construction
Lesson 1 : Matter and its characteristics
Mr.Ahmed Elbasha
Substances of densities less than the water density, float on water surface, while other substances of densities more than that of water sink.
Equal masses of different substances have different volumes ,also the equal volumes of different substances have different masses.
This is because of their different densities.

Liquid Density = 60/100 = 0.6 g/ cm³
Exercise
Exercise :
Knowing the density of natural milk is 1.03 g/cm3.
How can you identify the quality of milk you bought from a milk vendor?


Activity
• In the opposite figure
there is a water bath.
• Put some crushed ice
in the beaker, with a
thermometer.
• Place the water bath on
a flame and wait some
time.
• As ice melts, place the
flame away, record the
thermometer reading.

• Repeat the procedure
using solid wax instead
of ice, then record the
thermometer reading
as wax melts.

Is the melting point of wax the same as that of ice?

• What do you observe?

• Conclusion:

There are other characteristics of which other substances are different such as hardness, electric conduction and thermal conduction:

Hardness:
Some solids are soft at ordinary temperatures such as rubber.
Some substances need heat to get soften in order that to be easily shaped such as metals.
Some other substances are solids which can not be soften if heated such as coal and sulphur.


Boiling point
Boiling point:
it is the temperature at which a substance begins to change from a liquid state into a gaseous state.
life Application

l . Manufacturers heat metals to be molten, so that they could be easily shaped or even mixed to form alloys Like gold copper alloy used in making jewels, or nickel chrome alloy which is used in making heating coils.

2. Cooking pots are made up of aluminum or stainless steel alloy which does not rust, due to its high melting point

Melting point
Melting point
: it is the temperature at which matter begins to change from a solid state into a liquid one.

Melting points
of substances differ from each other, some have low melting points like butter, ice and wax, others have higher melting points like iron, aluminum, copper and table salt.

Density = Mass / Volume
Then ; Mass = Volume * Density
100 g = Volume * 1.03

Volume must be 100 * 1.03 = 103 Cm3

Also each substance has its own boiling point which identifies this
substance and distinguishes it from other substances.

Electric conduction:

Some substances are good electric conductors such as metals (copper and silver) also acid and alkali solutions and some salts solutions.

Some other substances do not conduct electricity such as gases, sugar solution, or solution of hydrogen chloride in benzene. In addition to some other solid elements such as sulphur and phosphorus.

Thermal conduction:

Substances differ in their abilities of heat conduction..
Some are poor thermal conductors like wood and plastics.
Other substances are good heat conductors like metals (iron - copper - aluminum


Life Application
1. Electric cables are made up of copper or aluminum.
2. Cooking pots are made up of aluminum.
3. Cooking pots have handles made up of wood or plastic.
4. The handles of screw drivers are made up of plastics or wood while the rest of the screw drivers are made of steel iron.

Metals and chemical activity:
Why do metals lose their luster when they are exposed to air for a period of time?

Some elements are very active as potassium and sodium which reactwith oxygen as soon as being exposed to humid air. Other substances like iron, aluminum and copper react with oxygen if left in air for some days since they have less chemical activity.
Some other substances find great difficulty to react with oxygen like silver, platinum and gold since they are not active; so these substances are used in making jewels. Also substances, like gold and silver, which are chemically poor active are used to cover other substances whichrapidly gain rust, as iron to protect them from corrosion.

Life application

1. Painting metallic bridges and the light posts in streets from time to time in order to protect them against rust.
2. Spare parts of cars are coated with grease to protect them getting rust.
3. Cooking aluminum pots are washed using a rough material to remove any layer formed on the pot surface.


Summary
Density
: mass of unit volume of a substance
Melting point
: it is the temperature at which a substance changes from a solid state into a liquid one.
Boiling point:
it is the temperature at which a substance changes from a liquid state into gaseous one.
Substances differ in their characteristics as: colour, taste, smell, density, melting
and boiling points, hardness, thermal conduction, and electric conduction.

Substances have different chemical activities.
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