Sunday, 6 March 2016

HEARTS

These are some of the hearts that we did on Valentine's Day.
I´ll post the others later.

Saturday, 5 March 2016

SISTEMA DE MEDIDAS

En este tema vamos a aprender a usar medidas de longitud:
A utilizar medidas de superficie:
Expresiones complejas e incomplejas:
Operaciones con unidades de superficie:

Iniciación al volumen:

Unidades de medida de volumen del Sistema Métrico Decimal:

Volumen y capacidad: la correspondencia entre las unidades de volumen y las unidades de capacidad:
Aquí tenéis un modelo de examen del tema, con las soluciones para que podáis practicar:

WHAT'S OXIDATION?

Oxidation is a chemical reaction in which an atom loses one or more electrons to oxygen atoms. Oxidation causes changes to the properties and appearance of substances.
Types of oxydation:
Rusting: When iron is exposed to oxygen in the air, its electrons are lost. Rusting can cause problems in vehicles. To prevent this, vehicles are painted.
 

Oxidation in fruit: When the fruit is exposed to the air, its electrons are lost. When this happens, a chemical change takes place, and the part of the fruit that has oxidised is no longer good to eat.


Fermentation: is a chemical reaction in which an organism such as yeast or bacteria, changes sugar and carbohydrates into alcohol or an acid.

Thursday, 3 March 2016

WHAT ARE CHEMICAL CHANGES?

Chemical changes occur when one or more substances combine to form a new substance. A chemical change is non-reversible.
Image from sjesci 
The process in which two or more substances combine chemically is called a chemical reaction.
Some chemical reactions produce thermal energy; these are called exothermic reactions.


Other reactions absorb thermal energy; these are called endothermic reactions.


Combustion, or burning, is the name for a chemical reaction in which oxygen combines with a fuel, such as wood, coal or natural gas. It is an exothermic reaction.


We use combustion in various ways:
  • Petrol and diesel are burnt to power vehicles and to heat homes.
  • Coal is burnt in power stations to generate electricity.
  • We burn natural gas to cook and heat our homes.
Combustion causes problems:
  • Most fuels produce carbon dioxide during combustion. Carbon dioxide contributes to global warming.
  • Burning coal, petrol or diesel produce particles that pollute the air.
  • Burning coal and diesel can produce an acid called sulphur dioxide. If sulphur dioxide mixes with rainwater, it produces acid rain.

Tuesday, 1 March 2016

HOW ARE MIXTURES SEPARATED?

Mixtures can be separated into their original components (because the components haven't been chemically combined). Several techniques can be used to separate mixtures: for example, filtration, distillation, evaporation or dissolution.

Filtration: This technique can be used to separate an insoluble solid from a mixture.
Picture via eschooltoday
Evaporation: This technique can be used to separate a soluble solid from a solution.
Photo via bbc.co.uk
Photo via bbc.co.uk
Photo via bbc.co.uk

Distillation: This technique can be used to separate a liquid from a solution or to separate two liquids.
 
Dissolution: This technique can be used to separate a soluble solid from an insoluble one.