NS:4. UNIT 5: "MATTER AND ENERGY

 

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.

5.7.-Light

-        Light is the fastest form of energy.

-        Light travels through transparent and translucent materials such as glass or plastic but not through opaque such as wood.

-        Light comes from:

o   Natural sources.- The Sun

o   Artificial sources.- Light bulbs. 

Ø  Reflection.- When light hits an object and changes the direction.

Ø  Refraction.- When light passes from one substance into another.

 

5.8.-Heat

-        Heat makes thermal energy where the particles move faster.

-        Thermal energy flows from a warm to a cooler substance.

Ø  Materials and heat

-       Metal transfers heat easily. These types of materials are called thermal conductors.

-       Materials that do not conduct heat are called thermal insulators.