How do detergents clean?
1. Read the text and fill in the gaps with these words.
detergent
soapless
droplet
soluble
hydrogen
hydrophilic
hydrophobic
A detergent molecule, whether soapy or 1 ______________ , consists of two
parts. There is a polar, 2 _______________ (water-loving) end. Which is
soluble in water and is often called the ‘head’. There is also a non-polar,
3 _____________ (water- hating) end, which is soluble in fats and oils and is
called the ‘tail’. The tail is a long hydrocarbon chain, that is, a chain of carbon
atoms with 4 ______________ atoms attached to them. Dirt clings to
surfaces, skin or fabric, by an oil film that surrounds the dirt particle. The tail
end of 5 ______________ molecules will attach to the oil film around the dirt
particle and completely surround it, making a tiny 6 ______________ or
micelle. As all the tail ends are attached to the oil around the dirt particle, only
the hydrophilic end of the detergent molecules will be exposed to the surface.
As these are 7_______________ in water, you can now wash away the dirt.
Common chemical substances and their uses in the home
2. Put the word and phrases in the correct places in the table. One item
appears twice.
alum ●antacid ● citric acid ● Glauber’s salt ● insect stings
●laxative ●monosodium glutamate ●oven cleaner ● raising agent
●salt ●sodium chloride
● sodium hydrogencarbonate
●sodium
hydroxide
●vinegar
●washing soda
Common name
caustic soda
Milk of magnesia
4 _____________
Chemical name (of active
ingredient)
Type of
chemical
Uses
1 _______________________
alkali
drain cleaner, 2___________
grease remover
magnesium hydroxide
alkali
3 ____________________
acid
cooking, pickling, cleaning
and treating some
5______________
salt
raising agent in baking, an
antacid, in dry powder fire
extinguishers, treating
insect bites, for cleaning
salt
7____________ in baking
salt
to make soaps and glass
cleaners, also used as a
water softener
salt and acid
antacid
10 _______________________
salt
cooking and preserving
foods.
magnesium sulphate
salt
11 _________________
sodium sulphate
salt
laxative
acetic acid solution (ethanoic acid)
6 __________________________
baking soda
__________________________
baking powder
8______________
sodium hydrogencarbonate
sodium carbonate
sodium hydrogencarbonate and
Enos salts
9 _________________________
table (common) salt
Epson salts
12 ____________
sodium aluminium sulphate
salt
water purification, also
baking powder
toothpaste
sodium monofluoroposphate
14 ________
prevents tooth decay
MSG
15 ____________________
salt
enhances flavour in food
13 ____________
Solutions
3. Underline the correct word in each sentence.
1 Solutions are (homogenous/ heterogeneous) mixtures, which are formed
when a solute completely dissolves in a solvent.
2 The (solute/ solvent) is the substance that dissolves, while the (solute/
solvent) is the substance that does the dissolving.
3 It is generally present in the (lesser/ greater) quantity in the mixture.
4 When the solvent used to make the solution is water then the solution is
said to be (aqueous/ non-aqueous).
5 However when the solvent used is liquid other than water, then the solution
is said to be (aqueous/ non-aqueous).
6 Liquid solutions are (translucent/ transparent) but not necessarily
colourless.
7 They allow (light/ dark) to pass through without being scattered.
8 The dissolved particles are very small, from 0.1 nanometre to 1 nanometre
therefore they cannot be seen with the (nude eye/ naked eye) or even be
removed by normal filter paper.
9 The dissolved (articles/ particles) do not settle out if the solution is allowed
to stand for some time.
Solvents in stain removal
4. Match these stains with the correct paragraph to show the stain can be
removed.
blood ●chocolate
● paint
●varnish
●coffee/tea
● grease/oil
● ink
●nail polish
1 _________________ - Gloss is best removed whilst wet with turpentine or
white spirit. Some water –based versions can be removed with hot water and
detergent.
2 _________________ - If the stain cannot be removed by warm and soap,
pour on boiling water, provided that this will not damage the fabric. Or use
biological washing powder. If this does not work, dab with dilute hydrogen
peroxide.
3 _________________ - If stains cannot be removed with soap and hot water,
try biological detergent which contains bleach.
4 _________________ - Water-soluble versions of this substance can be
removed by washing with soap and water. However, many stains made by
this substance can be removed by soaking the stain in milk for 1 or 2 days,
changing the milk as it becomes discoloured. Ethanoic acid and methanol
are non- aqueous solvents that can dissolve these stains.
5 _________________ - Rub with alcohol. The wash with warm water and
soap.
6 _________________ - Soak in cold water until stain turns lighter brown.
Then wash in warm water and detergent.
7 _________________ - Remove with acetone which is an organic solvent.
8 _________________ - Wash in warm water and soap, or use clean white
blotting paper, a piece on each side of the stain, and iron with a warm iron to
remove as much of it as possible. Gasoline is non-aqueous solvent that
removes these stains.
Properties of acids and alkalis
5. Sort the characteristics of acids and alkalis in the correct columns. One
of the characteristics applies to both.
Acids….
Alkalis…
1
7
2
8
3
9
4
10
5
11
6
12
a …. are corrosive
b …. are slippery when touched, that is they feel soapy.
c ….. are soluble in water.
d …. are the oxide or hydroxide of a metal.
e …. have a sour taste.
f …. react with acids to give a salt and water only.
g …. react with bases/alkalis to produce a salt and water only.
h …. react with fatty acids in the skin to form soap.
I … react with many materials and some can damage human tissue.
j … release hydrogen ions when dissolved in water.
k … turn blue litmus paper red.
Types of solutions
6. Read the text and complete the table.
There are different types of solutions. We often think of solutions as being
formed between a solid solute and a liquid solvent. However, gases and
liquids can be solutes and solvents too.
There are solutions which are made up of a solid in a liquid where the solute
is a solid and the solvent is a liquid. Examples of this are sugar in water, salt
in water and iodine in ethanol.
Oxygen in water, carbon dioxide in water in fizzy drinks are examples of
solutions where there is gas in a liquid. This is where the solute is a gas and
the solvent is liquid.
It is also possible to have a solution which is a liquid in a liquid where both the
solute and the solvent are liquids. Examples of this are alcohol in water and
syrup in water.
Type of solution
solid in liquid
gas in liquid
liquid in liquid
Solute
solvent
examples
7. Choose the correct answers.
Formic acid is an acid
in the juice of fruits such as oranges
that irritates the skin. It is present in ant
bites.
that is the main part of vinegar.
Sodium stearate is
a compound used for making soap,
paper, etc.
a sulphuric acid that is used to make
soapless detergents.
the chemical name for soap.
Ascorbic acid is
a compound containing carbon and oxygen
a chemical compound produced from
sulphuric acid.
vitamin C.
A disinfectant is a
liquid used for washing clothes or dishes.
A colloid is a
type of alcohol used as a fuel.
substance that is between a solution
and a suspension.
solid fatty acid.
Aqueous means
not mixing together to form a
solution.
substance used for cleaning injured skin.
containing water.
chemical substance that kills bacteria etc.
not containing water.
8. Match the sentence beginnings and endings by reordering the endings
on the right.
Citric acid
Lactic acid
Lactic acid
Lactic acid
is found in sour milk.
is also formed during anaerobic respiration in animals and
bacteria.
is found in citrus fruits.
in is found in grapes.
Hydrochloric acid
causes muscle cramps.
Ethanoic acid
is vitamin C, so can be found in many green, leafy vegetables.
Tartaric acid
Ascorbic acid
is made in the stomach where it aids digestion.
is found in vinegar.
9. Use the words to complete the statements that follow:
acidity
Calcium hydroxide
neutralize
citric
alkaline
carbonates
neutralization
oxide
In most cases acids and alkalis are used in the home for
reactions. Rust stains can be removed by treatment with lime juice. Lime juice
contains
acid while rust is an
of iron. Therefore the two react to form a salt and water. Acidic soils are less
fertile, so farmers neutralize the soil, usually with slaked lime or
before using it. Wasp stings are
, so they can
be treated with a mild acid such as vinegar, which contains acetic acid to
neutralize the alkali in the sting. This helps to reduce the pain. The term
‘neutralization’ is used to describe any reaction which reduces
For example, when a carbonate reacts with an acid to form salt, water and
carbon dioxide, the carbonate is said to have neutralized the acid.
are commonly used in home remedies. For example, bee stings and ant bites
which are acidic can be treated with baking soda (sodium hydrogencarbonate)
to
them and so reduce the irritating effect.
10.
Use the words to complete the statements that follow:
neutral
hydrogen
oxide or hydroxide
salt
filtration
combination
Acids are substances that release
Acids turn litmus paper
A base is the
red
homogenous
ions in solution.
.
of a metal.
A neutralization reaction occurs when an acid reacts with a base to form
and water only.
On the pH scale pH7 is
A mixture is a
combined.
Solutions are
.
of substances which are not chemically
mixtures.
The components of a suspension can be separated by
11.
Suspensions
In a suspension the solid particles do not dissolve but are suspended in
the liquid. They will eventually separate or settle out if the mixture is left
to stand. So, a suspension is an example of a heterogeneous mixture
because the solid component can be seen separately from the liquid
component in the mixture. The solid particles are also large enough to be
filtered out. Examples of suspensions are soil and water and powdered
chalk in the water. Suspensions scatter light that is they do not allow
light to pass through completely. So they look cloudy.