there are many different types of acid for example car batteries contain sulfuric acid citrus fruits like lemons and lime contain citric acid the stomach contains an acid called hydrochloric acid vinegar contains ethanoic acid and fizzy drinks contain carbonic acid not that you can taste all of these acids that we have in these examples but a common theme amongst the acids is that they are all sour [Music] there are also a number of different alkalis for example toothpaste contains sodium hydroxide soap contains sodium hydroxide and potassium hydroxide and cleaning products for example bleach contains sodium hydroxide and alkalis all have in common the fact that they are soapy some acids and alkalis are safer to use than others for example the ones on the screen like fizzy drinks and vinegar and fruits soaps and toothpastes are everyday items that are safe for us to use others like car batteries and cleaning products are more dangerous and we might have to wear protective equipment such as gloves safety glasses or even goggles when handling some of these acids and alkalis in the lab you will notice different safety symbols on the acids and alkalis the two most common ones that you'll find on bottles of acid and alkali solutions are the irritant which means that if you get that acid or alkaline or skin you will need to wash your hands or corrosive which means that you might need to use more protective equipment such as gloves and bigger goggles when using these acids and alkalis in the lab there is a variety of different acids that you might use the most common ones are hydrochloric acid hcl sulfuric acid h2so4 and nitric acid hno3 you may have noticed that what's the same about each of these chemical symbols is that they all start with hydrogen because acids all contain hydrogen some examples of common alkalis that you might see are sodium hydroxide ammonium hydroxide and calcium hydroxide and you'll notice that with the alkalis the common theme is this hydroxide part [Music] so with the acids you'll see the hydrogen and with the alkalis you will see the hydroxide with colorless solutions we can't tell the difference between acids and alkalis so we use an indicator called universal indicator to help identify the acids and the alkalis so with these colorless solutions labeled a to g it's really difficult to tell which ones are acid and which are alkaline but if we add into those solutions our universal indicator will be able to tell the acids from the alkalis as we place the universal indicator into the solutions you'll see that we will end up with a range of different colours so we have red for this colorless solution that's a [Music] an orange color 4b a yellow color 4c [Music] a green color for d going darker there for e going into a dark green bluey color for f and then a purple color for g so we can look at the color that our solutions went when we added universal indicator and we can compare these colors on the ph scale the ph scale only works with universal indicator in another video i'll go through different indicators that we can use to identify acids and alkalis however these will not work with a ph scale so it's only a universal indicator that will give this range of colors so from the colors red to yellow from the range 0 to 6 is where we would find our acids so those that went red orange and yellow are our acids the alkali colours go from darker green to purple and these are from ph 8 to 14. and in the middle at ph 7 it's neither an acid nor an alkali so it's called neutral the numbers on the ph scale help tell us the strength of the acid so at ph 7 is neither an acid nor an alkali it's neutral so that's where we'd find pure water and then looking at something that might have turned orange or yellow in universal indicator would be things like tea and coffee these are very close to water at neutral so these are very weak acids and then as we go down on the ph scale here we're going to go to the end where we would find our really strong acids so getting a bit stronger you'd have things such as your vinegar and even stronger things such as stomach acid and citric acids carbonic acids that you'd find around ph2 and even stronger again the acids that we would find in car batteries on the other side of this ph scale where we find our alkalis near water so near this ph 7 here is where we would find our weak alkalis and as the numbers get bigger down the end here is where you'd find your strongest alkalize so the weaker alkalis are things that we use every day such as toothpaste and soap and then our more dangerous cleaning products like bleach we would find further down in the stronger alkali section of the ph scale so not only does the ph scale give us an indication of whether something is an acid or an alkali the range of colours also tells us whether it is a weak acid a strong acid a weak alkali or a strong alkaline hi guys if you enjoyed that last video then please click on the screen to 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