Chemistry

  Unit: 1 History of a Nation   Lesson: 1 Prophet Mohammad (PBUH) Page 7   Lesson: 2 The Beginning of Islam 11   Lesson: 5 The Ayyubid Empire Page 22 Lesson: 5 The Ayyubid Empire Page 23 Lesson: 5 The Ayyubid Empire Page 24 Unit: 2, Individual Differences   Lesson: 1 What is a Phobia? Page 34    Lesson: 2 Feeling of Anxiety Page 38  

  Emulsions: An emulsion is a finely dispersed mixture of two or more liquids that do not dissolve in each other. Emulsifiers: Salad cream also contains oil and water. Salad cream has egg yolk added. This keeps the oil droplets mixed with the water. It stops the oil and water separating out into layers. A substance that does this is called an emulsifier . Detergents: Many detergents are made from the products of crude oil. Washing-up liquid is an example. Detergents are substances which help the cleaning action of water. Water is good at dissolving many things. However, it cannot dissolve oil or grease. This is where detergents help. They act as emulsifiers . They remove grease and keep it dispersed in water. Soaps: We can summaries the reaction as: Oil/fat   +   sodium hydroxide   à   soap   +   glycerol Making soap is called saponification . Preservatives and anti-oxidants: Fresh foods soon ‘go off’ as they are attacked by ba...

  Grade 7    Chemistry                                                                      Question 1                   The particles move from an area of low concentration to an area of high concentration is called diffusion. F Molecules are groups of 2 or more atoms bonded together. T Elements contain only one type of atom. T Compounds contain 2 or more types of atom. T Chemists use a kind of short-hand to describe molecules. It's called the symbol. F Question 2                   The particles move f...