S1 ScienceAcids and Bases

REVISION

I have investigated different water samples from the environment and explored methods that can be used to clean and conserve water and I am aware of the properties and uses of water.

SCN 2-18a

NEW LEARNING Having taken part in practical activities to compare the properties of acids and bases, I have demonstrated ways of measuring and adjusting pH and can describe the significance of pH in everyday life.SCN 3-18a

Explain what the pH scale is

Learning what pH is used to measure. Colouring in a pH scale to show the different values. Watch a video to show us how to measure pH

What are acids and bases?

You may not have heard of bases but you’ve probably heard of acids

Acid – a substance with a pH less than 7

Bases – a substance with a pH more than 7

The pH Scale

• The pH number of a substance is linked to how concentrated an acid or base is

• Water is neither acid nor base so is pH 7, in the middle

The pH scale extends from pH 1 to pH 14.

To find out pH you must use an indicator like UNIVERSAL INDICATOR.

Most indicators change colour dependent on pH.

The diagram below shows how colour with universal indicator links to pH number and how acidic or alkaline a substance is.

What is an indicator?

• Indicators work simply by changing colour when they come into contact with certain substances

• They are used to show if a substance is acidic, alkaline or neutral

Indicators

• Indicators in general come from plant materials .e.g. beetroot, blackcurrants or brightly coloured flower petals

• Universal indicator is a mixture of several indicators.

• How to test acids and alkalis

Explain what the pH scale is

Learning what pH is used to measure. Colouring in a pH scale to show the different values. Watch a video to show us how to measure pH

S1 ScienceAcids and Bases

REVISION

I have investigated different water samples from the environment and explored methods that can be used to clean and conserve water and I am aware of the properties and uses of water.

SCN 2-18a

NEW LEARNING Having taken part in practical activities to compare the properties of acids and bases, I have demonstrated ways of measuring and adjusting pH and can describe the significance of pH in everyday life.SCN 3-18a

Starter Questions

• What does the pH scale measure?It measures how acidic a substance is

• What colour is a neutral solution on the pH scale?

• Green

Measure how acidic substances are.

Learning what the pH of a substance is and doing An experiment to measure the pH of some everyday substances.

What is a hazard?

• A hazard is something that can cause you danger

• We should use symbols to represent hazards because it’s easy to understand

• Symbols are brightly coloured so that you notice them

Testing the pH of substances

• For liquids use a dropper to put a few drops on a dimple tray

• For solids use a spatula• Add 3 drops of universal

indicator • Do not stir solids – this can

change the colour

• Note down the colour and compare this to the chart you’ve been given

• Acids – red, orange, yellow• Neutral – green• Alkali – dark green, blue, purple

Substance Colour Acid, neutral or alkali

http://www.chemicroc.com/index.php?page=2

• http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks3/science/acids/

• Test the pH of common household substances

Measure how acidic substances are.

Learning what the pH of a substance is and doing An experiment to measure the pH of some everyday substances.

S1 ScienceAcids and Bases

REVISION

I have investigated different water samples from the environment and explored methods that can be used to clean and conserve water and I am aware of the properties and uses of water.

SCN 2-18a

NEW LEARNING Having taken part in practical activities to compare the properties of acids and bases, I have demonstrated ways of measuring and adjusting pH and can describe the significance of pH in everyday life.SCN 3-18a

Starter Questions

• Name a household acidVinegar, tomato sauce, lemon juice

etc.

• Name a household base• Bleach, toothpaste, bicarbonate of

soda

Describe how household acids are different from laboratory acids

Learning the names of some common laboratory acids, carry out an experiment with these acids

Acids

• A household acid is something that we find at home e.g. vinegar, tomato sauce, orange juice etc.

• A laboratory acid is one that is used in the laboratory. Common laboratory acids include hydrochloric acid, sulphuric acid and nitric acid

Experiment

• Test the pH of some household acids and compare them to the pH of laboratory acids

Substance pH number

Questions

• Generally which is more acidic, household acids or laboratory acids?

• You put vinegar on your chips, but would you put hydrochloric acid (or any laboratory acid) on food and eat it? Explain your answer.

Describe how household acids are different from laboratory acids

Learning the names of some common laboratory acids, carry out an experiment with these acids

Starter Questions

• Is vinegar an acid or base?

• Is cola an acid or base?

S1 ScienceAcids and Bases

REVISION

I have investigated different water samples from the environment and explored methods that can be used to clean and conserve water and I am aware of the properties and uses of water.

SCN 2-18a

NEW LEARNING Having taken part in practical activities to compare the properties of acids and bases, I have demonstrated ways of measuring and adjusting pH and can describe the significance of pH in everyday life.SCN 3-18a

Describe what a base is, explain that an alkali is a special type of base

Learning the names of some common laboratory bases, carry out an experiment with these bases

Bases

• Most of you will have heard of acids before

• How many of you have heard of bases?

• They are used everyday too

Household bases

Some cleaning products have a pH

MORE than seven. This meansthat they are a base

• Oven cleaner • Bleach

You wear gloves because basescan be corrosive just like acids

Common Bases

• Test the pH of some household bases and compare them to the pH of laboratory bases

Substance pH number

What is an alkali?

• An alkali also has a pH of more than seven

• How is it different from a base?

• Both have a pH of more than seven, but alkalis also dissolve in water

BasepH more than 7

AlkaliAlso dissolves in water

Try these two bases…

• Add half a spatula of sodium oxide to a test tube then add water – what happens?

• Add universal indicator and note the colour

• Next add half a spatula of sodium carbonate to a test tube then add water – what happens?

• Add universal indicator and note the colour

Questions

• Explain what happened when you added water to the sodium oxide

• Can we call this an alkali as well as a base?

• Explain what happened when you added water to the sodium carbonate

• Can we call this an alkali as well as a base?

Alkalis

Household Lab

sodium hydroxidelime waterammonia solutionbicarbonate of

sodaoven cleanerdishwasher powderbleachhard soap

oven cleanerdishwasher powderbleach

hard soap

sodium hydroxidelime water

ammonia solutionbicarbonate of soda

Put these alkalis into a table. Decide if they Are household alkalis orlaboratory (lab) alkalis