- C1 exam
- Vegetable oils do not dissolve in water. If oil and water are shaken together, tiny droplets of one liquid spread through the other liquid, forming a mixture called an emulsion.Emulsions are thicker (more viscous) than the oil or water they contain. This makes them useful in foods such as salad dressings and ice cream. Emulsions are also used in cosmetics and paints. There are two main types of emulsion:oil droplets in water (milk, ice cream, salad cream, mayonnaise)water droplets in oil (margarine, butter, skin cream, moisturising lotion).
- Emulsifier molecules have two different ends:a hydrophilic end - 'water-loving' - that forms chemical bonds with water but not with oilsa hydrophobic end - 'water-hating' - that forms chemical bonds with oils but not with water.Lecithin is an emulsifier commonly used in foods. It is obtained from oil seeds and is a mixture of different substances.
- The hydrophilic 'head' dissolves in the water and the hydrophobic 'tail' dissolves in the oil. In this way, the water and oil droplets become unable to separate out.
- Atomic Structure
- The protons and neutrons are found in the nucleus at the centre of the atom. The nucleus is very much smaller than the atom as a whole. The electrons are arranged in shells around the nucleus.
- The number of electrons in an atom is always the same as the number of protons, so atoms are electrically neutral overall.Atoms can lose or gain electrons. When they do, they form charged particles called ions:if an atom loses one or more electrons, it becomes a positively charged ionif an atom gains one or more electrons, it becomes a negatively charged ion
- The periodic table has eight main groups. For example, Group 1 contains very reactive metals such as sodium (Na), while Group 7 contains very reactive non-metals such as chlorine (Cl).There are no compounds in the periodic table, because these consist of two or more different elements joined together by chemical bonds.
- Crude Oil
- Crude oil is a mixture of hydrocarbons. The crude oil is evaporatedand its vapours condense at different temperatures in the fractionating column. Each fraction contains hydrocarbon molecules with a similar number of carbon atoms and a similar range of boiling points.
- A tall fractionating column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling pointscondense at the bottom and substances with lower boiling points condense on the way to the top.
- Fractional distillation separates a mixture into a number of different parts, called fractions.
Similar Chemistry resources: