C1a Topic 6 Making Changes Revision

Investigate and identify the uses of the following common compounds – ammonia – carbohydrates – carbon dioxide – caustic soda - – citric acid – ethanoic (acetic) acid – hydrochloric acid – phosphoric acid – sodium chloride (common table salt) – water.

Describe the use of hazard labels in the chemistry laboratory

Describe the use of sodium hydrogen carbonate as baking powder. Baking powder and self-raising flour contain sodium hydrogencarbonate (also known as sodium bicarbonate). When sodium hydrogencarbonate is heated, it decomposes to make sodium oxide, carbon dioxide and water. What effect does this reaction have on dough as it is being baked? Photo credit: © 2007 Jupiterimages Corporation The carbon dioxide released during the reaction creates tiny bubbles, which help the dough to rise.

Represent chemical reactions in this unit by word equations Write word equations for these reactions: Magnesium burned brightly reacting with the oxygen in the air to form magnesium oxide. magnesium + oxygen  magnesium oxide Hydrochloric acid reacted with the calcium hydroxide to give water and calcium chloride calcium chloride + water  calcium hydroxide hydrochloric acid Electrolysis of aluminium oxide produced aluminium metal and oxygen gas oxygen + aluminium  aluminium oxide

Gas Test Result Carbon dioxide Ammonia Oxygen Hydrogen Chlorine Know how to test for: hydrogen, oxygen carbon dioxide, ammonia and chlorine Gas Test Result Carbon dioxide Ammonia Oxygen Hydrogen Chlorine Limewater Cloudy Damp red Litmus paper Blue Glowing splint Relights Lit splint Squeaky pop White Litmus paper

Interpret data linking a chemical in food with a health impact, recognising that a correlation does not imply a cause (HT) It can be hard for scientist to prove or disprove that there is a risk of consuming a food. Can you think of any problems of testing ingredients on humans? Most research works by controlling all the factors in the experiment. Is it possible to control the diet of a human? It many take many years for side effects to show in humans. How long should new ingredients be tested for? Genetics means that some people are more likely to react to substances than others. On how many people should an ingredient be tested before it is declared safe? Recent studies have suggested that combinations of additives might cause health problems. Should scientists Should scientists test foods as a whole or the individual chemicals?

Can cooking food make it harmful? In 2002, scientists found high levels of acrylamide in cooked starchy foods. Acrylamide causes cancer in animals, so this discovery was very worrying. Cooking starchy foods at high temperatures can cause arclyamide to form. Should we banned starchy foods from school canteens? Studies have found high levels of acrylamide in chips, crisps, breakfast cereals and crisp breads. Teacher notes More information about acrylamide is available at: http://www.eatwell.gov.uk/healthissues/factsbehindissues/acrylamide http://news.bbc.co.uk/1/hi/health/2702241.stm Photo credit: © 2006 Jupiterimages Corporation Further research suggested that the levels of acrylamide in an average diet would not increase the risk of cancer. This is a controversial topic and research is ongoing.