Science - Chapter 9.1-9.3

Why do lemons have a sour taste?

Because they contain acids

What are the 3 most common acids used in school laboratories?

hydrochloride acid, sulphuric acid, nitric acid

What taste do acids have?

Sour taste

Fill in the blanks: Acidic solutions can conduct ____________.

electricity

Fill in the blanks: acids can be used as _______________ to prevent food from going bad.

preservatives

Fill in the blanks: some household cleaners contain acids to help remove ___________.

stains

Why can acids act as preservatives?

Microorganisms cannot grow or reproduce in acidic conditions

What acid is used to make fertilisers?

sulphuric acid

Vinegar contains which acid?

ethanoic acid

What feel does alkalis have?

slippery feel

What are the most common alkalis found in school laboratories?

sodium hydroxide, ammonia solution, calcium hydroxide

What taste do alkalis usually have?

bitter taste

Fill in the blanks: Alkaline solutions can conduct ___________.

electrcity

Which alkali is commonly found in kitchen cleaners and glass cleaners?

ammonia

Which alkali is commonly found in drain cleaners?

Sodium hydroxide

Which alkali is used for making batteries?

potassium hydroxide

Fill in the blanks: red cabbage extract can be used as a ______ ________ __because red cabbage contains__ ________ which changes colour in the presence of an acid or alkali.

natural indicator, pigments

What do we use to show the presence of acids and alkalis?

Indicators

What litmus is used to test acidic solutions?

blue litmus

What litmus is used to test alkaline solutions?

red litmus

We use litmus paper to classify solutions as acidic, alkaline and _________.

neutral

What is used to show the level of acidity or alkalinity of a solution?

universal indicator

What is the paper form of universal indicators?

pH paper

On a pH scale, what is the pH value of a acidic substance?

less than 7

On a pH scale, what is the pH value of an alkaline substance?

greater than 7

On a pH scale, what is the pH value of a neutral substance?

7

To measure accurately, what electronic instrument is used to measure pH values?

pH meter

What is an alternative to pH meters?

pH sensors connected with a data-logger

Alkalis and acids react with each other when they are mixed together. What is this kind of chemical reaction called?

neutralisation

What changes in neutralisation?

the acidity, alkalinity and pH value of the solution

Why is there a mild alkali in shampoos?

to help remove grease