Materials 1.4 Acids and Alkalis
Sc3: Materials and their
Properties
1.4 Acids & Alkalis
P.O.S.
Key Stage 3: 3d, 3e, 3f
LEARNING OBJECTIVES
· To recognise that acids have a sour taste (SAFETY SYMBOL)· To be aware that many everyday chemicals and foods contain acids
· To understand that acids can burn you and can be dangerous
· To know that we must wear goggles when using acids
· To recognise common hazard symbols associated with acids
· To observe the colour changes that occur when acids are added to certain plant dyes
· To observe the effect of acids on bicarbonate of soda
· To use litmus paper as a more sophisticated method of detecting an acid
· To use the term “indicator” when describing an acid
· To recognise that there are some substances that are not acids
· To recall that the opposite to an acid is an alkali
· To understand that a substance that is neither acidic nor alkaline is called neutral
· To know that tap water is (more or less) neutral
· To know that we can make an acid neutral if we add an alkali
· To understand that we can use neutralisation to treat bee stings, wasp stings and indigestion.
ICT
Internet research /LINKS
Food Technology /VOCABULARY
Acid, alkali, sour, burn, goggles, fruit, indicator, litmus, red, blue, neutral, neutralise, bee sting, wasp sting, stomach acid, corrosive, harmfulACTIVITIES
· Tasting various acidic substances e.g. citrus fruits, acid drops, vinegar· Create an exhibition of all the foods that contain acids
· Look at the labels of chemicals like limescale remover to consider the hazard symbols which represent corrosive and harmful
· Making plant dye extracts using beetroot and red cabbage. These can be used in liquid form (store in freezer) or soaked into filter paper to make an indicator paper when dry.
· Testing red cabbage and beetroot juice with common acids like vinegar and lemon juice to observe the associated colour changes.
· Using sodium bicarbonate powder to test for acids in liquids. Drip liquid onto the powder, bubbles of gas indicate that the liquid contains an acid. Acids will turn litmus red.
· Using neutral litmus paper to test a range of everyday liquids including water and some alkalis. Litmus will turn blue in an alkali and will stay the same colour in a neutral solution.
· Making a model bee sting with a test tube of acid. Add small quantities of sodium bicarbonate until the fizzing stops. Test the resulting solution to show that it is no longer an acid – hence no more sting. Wasp stings are alkaline in nature; we treat these with vinegar, an acid.
· Testing indigestion tablet to show that they contain alkalis.
· Adding indigestion tablet to a model stomach full of acid (test tube). The tablets will effervesce and neutralise the acid.
· Making a poster of common substances, acidic, alkaline and neutral.
· Use universal indicator to test soils for acidity/alkalinity /
RESOURCES
· Lemons, limes, oranges, grapefruits, vinegar, lemon juice· Sour tasting sweets e.g. old fashioned acid drops, “refreshers”
· Vinegar, lemon juice, pickled onions, apples
· Limescale remover (empty bottle only
· Beetroot, red cabbage, chopping board, knife, pans, cooker or Pyrex beakers and bunsen/tripod/ gauze
· Pestles and mortars or food blender, filter paper or access to fridge
· Sodium bicarbonate powder
· Spotting tiles
· Spatulas
· Dropping pipettes
· Litmus paper (blue and red, or neutral)
· Solutions of everyday acids as before
· Everyday alkalis e.g. soap solution, washing powder solution, Calgon (sodium carbonate) solution, sodium bicarbonate soultion
· Test tubes
· Paper, pens to make posters /
POINTS TO NOTE
OWN ACTIVITIES
POSSIBLE INVESTIGATIONS
· Which fruits/vegetables contain acid? Test with bicarbonate of soda or litmus paper.· For more able pupils: Which fruits contain the strongest acids? Taking equal quantities of fruit juices in test tubes, add measured quantities of sodium bicarbonate powder until the fizzing stops. The stronger the acid, the more bicarbonate that needs to be added.
· Which is the best indigestion cure?
Name:
Date Record Began:
Outcomes: NC Level 1 è NC Level 4
1 / · Has tasted foods containing acids· Knows that acids can be dangerous
1+ / · Can describe acids as having a sour taste
· Can name a food that contains acid
· Knows that acids can burn you
2 / · Understands the appropriate safety precautions to take when using acids e.g. goggles, wash off splashes etc
· Can describe the colour changes that occur when acids are added to plant dyes
2+ / · Recognises that using bicarbonate of soda is a method of testing for acids
· Recognises the safety symbols for corrosive and harmful
3 / · Understands that using indicators like litmus is reliable method of testing for acids
· Knows that litmus is an indicator which will turn red in an acid
3+ / · Recognises that there are some substances which are not acids
· Understands that litmus will turn red in an acid and blue in an alkali
· Knows that we can treat a bee sting with sodium bicarbonate
· Knows that we can treat acid indigestion with tablets which will get rid of some of the acid
4 / · Knows that litmus will not change colour in a neutral solution
· Knows that the opposite to an acid is called an alkali
· Understands that a substance that is neither acidic nor alkaline is called neutral
· Know that tap water is more or less neutral
Further Comments