UNIT 5: Matter and
energy
5.1.- Matter: mass,
volume, and density
- The matter is everything you can see like plants, rocks, and animals.
- Matter has mass, volume, and density.
Ø Mass
-
Mass is the amount of matter something
contains.
-
You can know matter with a balance or
scale.
Ø Volume
-
Volume is the amount of space an object
occupies.
-
You can measure volume with a measuring
cup and measure cylinder.
Ø Density
-
Density is the relationship between mass and volume.
-
You have to divide mass by volume.
D=M
V
·
High density.- When there is a large amount of mass
and low volume.
·
Low density.- When there is a low amount of mass
and large volume.
5.2.-Materials
-A material can be one or more types of
matter.
- Materials have different properties and
different uses.
They can be natural and manufactured.
Ø Natural materials.-They come from nature: animals ( wool, leather, silk), plants (
cork, wool, cotton), and minerals ( marble, gold).
Ø Manufactured
materials.- They are natural materials with chemical transformation. Examples:
plastic, paper, and steel.
Ø Properties of
materials.- The characteristics of materials
are called properties.
· Colour.- It depends on the light.
· Hardness.- It refers to how difficult is to change the shape.
· Resistance.- If it is easy or difficult to break.
· Elasticity.-If materials can return to their original shape.
· Thermal
conductivity.-If they can
transfer heat.
· Solubility.-If they can dissolve in liquids.
5. 3.-Physical changes
- There are physical changes when the matter can
change shape or state.
- They can be reversible or irreversible.
Ø Change in the
state.- A good example is water. It is
reversible
· Solidification..- When water becomes solid.
· Melting.-When water becomes liquid.
· Evaporation.- when water becomes gas.
· Condensation.-When water passes from gas to liquid.
Ø Change in shape.- When the matter is broken. It is irreversible.
5.4.-Mixtures
-
Matter
can be:
- Pure substance.-It consists of one type of matter.
- A mixture.-It consists of two or more types of
matter.
Ø Types
of mixtures
·
Heterogeneous mixture.-When the
different elements are visible and you can separate them. Example: a salad.
·
Homogeneous mixture.- When the different elements are not visible and you
cannot separate them. Example: a
milkshake.
Ø Separating
mixtures.- If you want to
separate mixtures, you have some techniques.
·
Evaporation.-You can use this method when you want to
separate solids from liquids.
·
Filtration.- You can use
this method when you want to separate solids from liquids or gases.
·
Distillation.- You can use
this method when you can separate two liquids.
·
Decantation.- You can use
this method when you can separate liquids from solids.
5.5.-Energy
-
Energy is
everywhere.
-
Energy can also
change forms.
Ø Forms
of energy
·
Mechanical energy.-It is produced by the movement. Example: cars.
·
Sound energy.-It is produced by
vibration. Example: singing.
·
Chemical energy.-It is produced by a chemical
reaction between two elements. Example: petrol.
·
Electrical energy.-It makes machines
works.
·
Thermal energy.-It flows from warm
to cool substances.
·
Light energy.-It is the fastest
form of energy. The main source of light is The Sun.
5.6.-Sources of energy
Ø Renewable
energy sources.- They are
unlimited and they will never run out.
·
Sunlight.-Solar
energy is used to generate electricity and to heat water.
·
Water.-Hydropower
plants transform water to electricity.
·
Wind.-Wind turbines transform air to electricity.
Ø Non-renewable
energy sources
-
They are limited and they cannot be replaced.
-
They are fossil fuels and uranium.
·
Fossil fuels.- They are coal, oil, and natural gas. They produce
pollution.
·
Uranium. It is a radioactive metal in nuclear power stations that produce
electricity.
