MODULE mod7A mod7B mod7C mod7D mod7E mod7F mod7G mod7H mod7I mod7J mod7K mod7L mod8A mod8B mod8C mod8D mod8E mod8F mod8G mod8H mod8I mod8J mod8K mod8L mod9A mod9B mod9C mod9D mod9E mod9F mod9G mod9H mod9I mod9J mod9K mod9L 7ha1
7Ha/1 Operation survival 1
Name _____________________________ Class ____________
When it rains, water runs into the ground. As it passes through the earth, the water is filtered by the rocks and the earth and eventually it comes out of the ground as clean water at a spring.
If you are lost in the wild you will need water to drink. If you cannot find a spring, you can easily make a water filter which will clean water in exactly the same way as it is cleaned when it goes through the earth.
Apparatus
- Plastic drinks bottle
with the bottom removed
- Small stones
- Sand (or soil)
- Moss or grass
- Ruler
- Muddy/dirty water to filter
Method
1 Push some moss into the neck of the bottle. You might need to use a ruler to push it down.
2 Put a layer of sand or soil on top of the moss.
3 Put a layer of small stones on top of the sand. Your finished filter should look like this:
4 Now try it out! Carefully pour some muddy water through your filter. If the first lot of water comes out muddy, keep trying.
Complete these sentences, using words from the box. You may need to use some words more than once.
clean dirt moss sand stones twigs washed away
The water filter makes _____________________ water out of dirty water.
The layer of _____________________ at the top traps leaves and _____________________ .
The layers of _____________________ and _____________________ trap
_____________________ particles in the water.
The first time the filter is used the water is not clean. This is because the _____________________
and _____________________ may have had bits of dirt on them.
When this _____________________ has been _____________________
_____________________ the filter lets clean water through.
[ knowledge ]
7Ha/2 Operation survival 2
When it rains, water runs into the ground. As it passes through the earth, the water is filtered and eventually it comes out of the ground as clean water at a spring.
Make your filter. It should look like this when it is finished.
Now try it out! Carefully pour some muddy water through your filter. If the first lot of water comes out muddy, keep trying.
1 Which things in the muddy water are trapped by the layer of stones?
2 Which things are trapped by the sand and moss?
3 Why do you need the layer of moss or grass?
4 The first lot of water you try to filter may not come out clean. Why do you think this happens?
Investigation - How fast does your filter make clean water?
- Stop clock
- Water filter
- Beakers
Planning
1 What could you change in your water filter to try to make it filter water faster? For instance, you could change the thickness of the sand layer, or the layer of moss.
2 How are you going to measure the speed at which it filters water? You must do it the same way each time to make your investigation a fair test.
3 Measure how fast your first filter works.
4 Now change your filter and measure how fast this one works. Write down what you changed, and how fast your new version filters water.
5 Does your new version still produce clean water?
6 Try changing your filter again and measuring the speed.
Recording your results
7 Present your results in a neat table. If you have enough results you might also be able to draw a line graph, like this:
Considering your results/conclusion
8 Explain what you have found out in your investigation.
[ planning, observing, presenting, considering ]
7Ha/3 Dissolving key words
1 Fill in the spaces using words from the box.
clear cloudy dissolves insoluble soluble solution sugar water
a Salt is a solid which _______________________ in water.
b Salt water is a _______________________ .
c We can see through salt water. A word to describe this is _______________________ .
d Solids, like salt, which dissolve in water are _______________________ .
e Chalk does not dissolve in water. It is _______________________ .
f When you mix chalk with water, the liquid turns _______________________ .
g When you mix sugar with water, the _______________________ is the solute and the
_______________________ is the solvent.
2 Using words from the box, write down:
a the name of a soluble solid _______________________
b a word which means the same as transparent _______________________
c a word that could describe orange squash _______________________
d the name of a solvent _______________________
[ knowledge, literacy ]
7Ha/4 Filtering
Filtering is used to separate a solid from a liquid.
Filtering will not separate a solid that has dissolved in the liquid.
1 Look at this list of mixtures. Circle the ones which can be separated by filtering.
salt and water flour and water sand and water
sand and milk sugar and water sugar and milk
2 Filters can be used when you are preparing food. Fill in the missing spaces in this table. The first two have been done for you
Equipment
Does it filter?
What goes through the 'filter'?
What is trapped in the 'filter'?
Teabag
yes
water and dissolved tea
tea leaves
Saucepan
no
-
Slotted spoon
Chip basket
Rolling pin
Flour sieve
Answer these questions in your book.
3 In the table, the things that filter have different sized holes. Explain why the teabag has different sized holes to the chip basket.
4 Imagine that you have a friend who has never seen a teabag.
a Explain how a teabag works and what it separates.
b Describe what a cup of tea is like if the teabag breaks.
7Ha/5 Water for life 1
Our bodies need water to stay alive. If we do not have any water, we will die within a few days.
Imagine that you have gone on a walking holiday in Scotland. You have plenty of food and clothes, but you have run out of water. There are no rivers or lakes near you, but the ground is very boggy.
You have this equipment with you.
1 a Where has the water in the bog come from?
b Will the water be salty?
2 If you dig a hole, it will fill with muddy water. You need to filter the muddy water to make it fit to drink.
a Which pieces of your equipment will you need?
b Explain how you will make your drinking water. Draw a labelled diagram to show how you would use your equipment.
Now imagine that you are stranded in the Arctic. You have the same equipment with you.
3 Snow is frozen water, If you melt it, you get drinking water. Explain how you would use your equipment to make drinking water out of the snow.
4 Look at the drawing. There is plenty of sea water near you.
a Explain why you cannot use this water for drinking.
b Explain why filtering will not help you to make drinking water from sea water.
7Ha/6 Water for life 2
Imagine that you are stranded in each of the places shown below. You have enough food and you have clothes, and you also have the following equipment:
1 You are stranded in Scotland. There are no rivers or lakes near you, but the ground is very boggy.
a Which pieces of equipment will you need to make some clean water?
b Explain how you will make your drinking water. Draw a diagram to show how you would use your equipment.
2 You are stranded in the Arctic.
a Explain how you would use your equipment to make drinking water from the snow.
b What other source of water is there? Could you use it for drinking? Explain your answer.
3 You are stranded on a desert island. There are no springs or streams.
Explain why you cannot get drinking water from sea water by filtering it.
7Ha/7 Other types of mixture
In a substance like milk, the two parts (fat and water) do not mix completely together, and we get a suspension, so called because the particles are held suspended in the liquid. Suspensions can be recognised because they are cloudy or misty. Some suspensions will separate out, like muddy water.
In other cases the particles will be so small that they will stay suspended for a very long time. These are known as colloids. The particles in a colloid may be too small to be seen under normal conditions, but show up when a beam of light shines on them. You can see this effect when headlights are used in fog. The tiny drops of water are suspended in the air and reflect some of the light. You will probably be familiar with many colloids, even if you don't realise it! There are many different types of colloid.
This table shows the names given to different types of colloid.
Substance 1
Substance 2
solid
liquid
sol (solid in liquid)
or
gel (liquid in solid)
emulsion
gas
aerosol (solid in gas)
solid foam (gas in solid)
aerosol (liquid in gas)
foam (gas in liquid)
Prepare a chart or poster showing examples of the different types of colloids that you find around the house, putting each one into the correct category. You may be able to draw pictures of the different types, or collect product labels.
Some examples that you could use are: milk, mayonnaise, smoke, jelly, hair spray, whipped cream, expanded polystyrene, shaving cream, toothpaste, dust, furniture polish and skin creams.
7Hb/1 Investigating water 1
How much salt is in two different samples of water?
- Evaporating basin
- Heat-proof mat
- Gauze
- Water samples
- Tripod
- Eye protection
Always wear eye protection when heating chemicals
Label this diagram using words from the apparatus list:
Fill in the missing words, using words from the box.
You may need to use the words more than once.
I will separate the water from the chemicals by ____________________ the water.
I will make it a fair test by using the ____________________ amount of water each time.
I will measure the volume of the water using a ____________________ ____________________ .
I will find out the ____________________ of chemicals by measuring the mass of the evaporating
basin when all the water has ____________________ .
I will wash the chemical out of the ____________________ ____________________ and then do
the same experiment again with the other sample of water. I will use the
____________________evaporating basin.
evaporated evaporating evaporating basin mass measuring cylinder same
Sample
Mass of basin and chemical
A
B
Sample ____________________ had the most chemical in it.
I know this because it had the greatest mass.
[ observing, knowledge ]
For a diagram of apparatus without leader lines and label lines see Summary Sheet 7H.
7Hb/2 Investigating water 2
All water samples contain chemicals which have dissolved into the water as it flowed through the ground.
You will be given some samples of water to investigate. Your task is to find out which water sample has the most chemicals dissolved in it. You will need to separate the chemicals from the water.
You must carry out a fair test. Make sure your work is accurate, because another group may be checking your results.
- Balance
1 Write a plan for your investigation. Show it to your teacher before you start.
You will need to think about these things:
- How much water will you use?
- How will you remove the water from the chemicals?
- How will you know how much chemical your samples contain?
- How will you make your experiment safe?
- How will you be able to check if your results are correct?
2 Present your results in a table.
3 Which sample contained the most chemical?
4 How do you know this?
Evaluation
5 Could you improve your method if you had time to do the investigation again? Explain your answer.
[ planning, observing, presenting, considering, evaluating ]
7Hb/3 Making pure salt from rock salt - practical
When salt is mined it comes out of the ground as rock salt. Rock salt is a mixture of solid rock and salt. You can make pure salt from rock salt in the laboratory.
- Rock salt
- Mortar and pestle
- Two beakers
- Stirring rod
- Funnel
- Bunsen burner
- Filter paper
Always wear eye protection when heating chemicals.
1 Crush some rock salt using the mortar and pestle.
2 Put the crushed rock salt into a beaker and add some water. Stir the mixture.
3 Carefully filter the mixture. The liquid that comes through the filter paper should be clear.
4 Put a little liquid in an evaporating basin and heat it. WEAR EYE PROTECTION.
5 The powder that is left in the evaporating basin should be pure salt.
1 Describe how you obtained pure salt from rock salt.
2 Draw a neat diagram to show how you evaporated the liquid.
3 Why did you crush the rock salt in Step 1?
4 What happened to the salt in the rock salt when you added water.
5 When you filtered the mixture, what was left in the filter paper?
6 Why didn't filtering remove the salt from the water?
[ observing, considering ]
7Hb/4 Making salt from rock salt 1
Rock salt is a mixture of rock and salt. The instructions below tell you how to make salt from rock salt.
Label the diagrams and fill in the missing words in the sentences. The words you need are in the boxes. You may need to use some words more than once.
1 Crush up the __________________________________ using a _________________ and
_________________. This makes sure that there is no _________________ trapped inside
bits of rock.
mortar pestle rock salt salt
2 Put the crushed up rock salt into a _________________ and add _________________ . The
is soluble and will dissolve. The bits of rock are _________________ and will not dissolve.
Stir the mixture to help the _________________ to dissolve.
beaker insoluble rock salt stirring rod water
3 Filter the mixture. The _________________ bits of rock will be trapped in the
_________________ . Salty water will go through the filter paper. The does not trap the salt
because the salt is _________________ in the water.
bits of rock conical flask dissolved filter paper funnel insoluble salty water
4 You can get the _________________ from the salty water by _________________ the
mixture. The _________________ evaporates and leaves the _________________ behind.
heating salt salty water tripod water
7Hb/5 Making salt from rock salt 2
1 Pure salt can be made from rock salt in the following stages:
A crushing B dissolving C filtering D evaporating
For each stage, explain what happens and why it is done. For instance, for 'crushing' you might write:
A The rock salt is a mixture of rock and salt. It is crushed to make sure that no salt is trapped inside bits of rocks, and to make the salt dissolve faster when water is added.
2 This diagram shows one way of getting salt from underground rock salt.
Not to scale
At A, water is taken from a nearby river. It is pumped down into the layer of rock salt (B). Salt in the rock dissolves (C) forming brine solution. Brine is pumped up to the surface (D).
a Why is there a large hole in the rock at the end of the water pipe?
b What is brine?
c Salt companies use the brine to make pure salt. What do they have to do to the brine to make salt from it? Explain your answer.
d Which of the four stages at the top of the page take place when salt is made in this way?
7Hb/6 Particles and dissolving 1
1 Fill in the gaps in these sentences using words from the box. Each word may be used once, more than once, or not at all.
The particles in __________________ are held together in a __________________
arrangement. The __________________ in water can move around.
When the salt __________________ , the salt __________________ are not
held together any more. They __________________with the __________________ particles
to form a __________________ .
The mass of the solution will be __________________ g.
If we had dissolved 20 g of salt in the water, the __________________ of the solution would
have been __________________ g.
100 110 120 130 dissolves fixed mix
particles salt solute solution water mass
2
This diagram shows a mixture of sand and salty water being filtered. Fill in the key and the gaps in these sentences using words from the box. You may need to use some words more than once.
You can use __________________ paper to separate __________________ from salty water.
The sand grains are too __________________ to go through the tiny __________________ in
the filter paper. The filter will not __________________the particles of salt, because they are
very __________________. They will fit through the gaps in the filter _________________ .
big filter gaps paper salt sand small trap water
7Hb/7 Using ideas about dissolving
1
Explain how you could prove that the salt was still in the water.
2 If you mix the salt with the water, how much salt water do you think you will get?
A less than 100 g
B exactly 100 g
C between 100 and 110 g
D exactly 110 g
E more than 110 g
Explain how you arrived at your answer.
3 If you evaporate the water, you will be able to get the salt back again. How much salt do you think you would get?
A less than 10 g
B exactly 10 g
C more than 10 g
D it is not possible to predict
Explain your answer
4 If you mix the salt with the water, how much salt water do you think you will get?
A less than 100 cm3
B exactly 100 cm3
C between 100 and 110 cm3
D exactly 110 cm3
E more than 110 cm3
Explain your answer.
5 Draw a labelled particle diagram to show why filtering will not separate salt from water.
7Hb/8 Gandhi and the Salt Act
Read this passage and then answer the questions below.
Salt is very important for the body, especially in hot countries.
The British ruled India at the beginning of the twentieth century. There was plenty of salt available in India, but the British Government passed laws to ban the Indians from making their own salt; they would have to buy it from the government instead.
In March 1930, at the age of 61, Mahatma Gandhi led a 241 mile march to the sea. At dawn, Gandhi walked down to the water's edge and picked a pinch of salt from the sand. Thousands of people quickly followed his example and made their own salt by taking a pan of sea water and letting the Sun evaporate the water.
Many people were arrested for doing this but eventually the law was changed again to allow anyone to make their own salt.
1 Why did the British Government ban the Indians from making their own salt?
2 Why did people make salt from the sea water instead of picking the salt up from the beach as Gandhi had done?
3 Would these people have made pure salt? Explain your answer.
4 In some countries there are salt lakes, which sometimes dry up in the summer. If you collected salt from the lake bed it would be mixed with sand. Design a method to separate the sand from the salt, using normal lab apparatus.
- Draw a diagram to illustrate each stage in your method
- Explain why you carry out each step of the process
7Hc/1 Distillation 1
Label the parts of the distillation apparatus shown below, using words from the box.
beaker flask heat Liebig condenser thermometer water in water out
---------------------------------------------------------------------------------------------------------
The water evaporates and forms steam. The ink does not evaporate.
The mixture is heated.
The water runs into the beaker.
The cold water flowing around the outside of the condenser cools the steam.
The mixture of ink and water is put into the flask.
The steam goes into the condenser.
The steam condenses to form pure water.
7Hc/2 Distillation 2
Label the parts of the distillation apparatus shown and describe what each part does in the process of distillation.
________________________________________________________________________________
7Hc/3 Not a drop to drink!
Your ship has sunk and you are in a small boat in the middle of the ocean. There is no pure water to drink. If you drink water from the sea you will die.
1 Sea water is a mixture. What is dissolved in sea water?
You need to make some drinking water. These things are in the boat with you:
First of all you tried filtering the water, like this:
The water in the pan was still salty.
2 Which part of your equipment was acting like filter paper?
3 Why was the water in the pan still salty?
You need to think of a different way of making drinking water.
You need to heat some sea water, collect the steam, and cool the steam so it condenses again.
4 How will you heat the sea water? Say which pieces of equipment you will use.
5 Which part of the sea water will evaporate?
6 How will you trap the steam?
7 How will you cool down the steam? (Hint: the handkerchief could be useful.)
8 What will you use to collect the condensed water?
9 Draw a diagram or a picture to show your apparatus.
7Hc/4 The history of distillation
When microbes called yeast feed on sugar one of their waste products is alcohol. This process is called fermenting. When a certain amount of alcohol has been made it poisons the yeast and they die. Beer and wine can never be stronger than about 15% alcohol, because the yeast cannot make more alcohol than this before they die.
People wanted alcoholic drinks that were stronger than beer and wine. Distillation is a way of getting the alcohol out of the mixture of alcohol, dead yeast and water.
Alcoholic drinks are usually distilled from a beer (made from a fermented grain like barley, oats or even rice) or from a wine (made from fermented grape juice). Other natural materials like potatoes and even treacle have been fermented and then distilled. If wine is distilled the product will be a brandy. If a beer is distilled the product will be a whisky.
Distillation has been used to separate a pure liquid from a mixture since 800 bc, when it is recorded that an alcoholic drink called Sochou was separated from rice which had been fermented by yeast, in Japan. The first recorded use of distillation to separate an alcoholic drink in Britain was in the sixth century (500 ad) when alcohol was separated from mead, which is made by fermenting honey. The first recorded distillation of whisky in Scotland did not occur until a thousand years later.
For centuries, distillation has also been used to separate oils and perfumes from natural materials. These were then used as medicines and scents, forming the basis of the modern medicine and cosmetic industries.
1 What was the first alcoholic drink made from?
2 How is mead made?
3 What are the main materials from which alcoholic drinks can be made?
4 What is the difference between brandy and whisky?
5 Why is distillation needed to make strong alcoholic drinks?
6 What other chemicals have been separated using distillation?
7Hc/5 What is in a barrel of oil?
When a barrel of crude oil is distilled, the following chemicals are obtained:
Description of chemical separated
Amount in barrel (percentage of barrel)
Hydrocarbon gases
2%
Naphtha
4%
Petrol
31%
Kerosene
11%
Gas oil & Diesel oil
30%
Fuel oil
18%
Lubricating oils, Waxes and Bitumen
1 Use the information from the table to plot a bar chart to show the amount of each type of chemical in the barrel of oil. Label each axis and each bar on the chart. Use the bar chart to help you answer the following questions.
2 Which type of chemical is there most of in a barrel of crude oil?
3 Which chemical is there least of in a barrel?
4 Use the data in the table to draw a pie chart to show the amount of each type of chemical.
5 Which chart would you use to explain about the parts of a barrel of oil to someone who doesn't know about oil? Explain why you chose this graph.
6 Research: try to find out at least two uses for each fraction in a barrel of oil.
[ knowledge, numeracy, research ]
7Hd/1 Chromatography of ink
Some students carried out the chromatography of different inks during their science lesson. Their results are shown below. Complete the table.
Chromatogram
Colours contained in the ink
Is the ink a mixture of colours or only one pure colour?
3
4
5
6
7Hd/2 Separating mixtures 1
Fill in the gaps in these sentences, using the words in the boxes. You may need some words more than once.
1 Filtering can separate a solid which does not ____________________ (like sand) from a
____________________ (like water). Filtering will not separate a dissolved solid (like
____________________ ) from water. Particles of ____________________ are trapped in
the ____________________ ____________________ , and the liquid goes through the
____________________ ____________________ .
dissolve filter paper liquid salt solid
2 Evaporating can separate a ____________________ solid (like salt) from water. The mixture
is until all the water has ____________________. The ____________________ is left behind.
dissolved evaporated heated salt
3 Distilling can separate a ____________________ from a dissolved solid. You can use
distillation to get ____________________water from salty water, or pure
____________________ from inky water. Distillation can also separate a mixture of different
____________________. The mixture is heated until the liquid ____________________ .
The gas is collected and ___________________down so that it ___________________ .
condenses cooled evaporates liquid liquids pure water
4 Chromatography can separate different chemicals, such as different ____________________
in ink or ____________________ ____________________. Spots of different dyes are put
on a piece of ____________________ paper, and the paper is put into a liquid. If the dyes
dissolve in water then ____________________ can be used for the liquid. If the dyes do not
dissolve in water a different ____________________ , such as ____________________ ,
must be used.
dyes ethanol filter food colouring liquid water
[ knowledge, literacy, revision ]
7Hd/3 Separating mixtures 2
1 Fill in the gaps in the table:
Separation method
Used to separate
Apparatus used
Examples
i
i filter paper
ii
iii
Evaporating
i a dissolved solid from a liquid
i evaporating basin
ii gauze
iv
v
i Distilling
C
Distilling
ii a mixture of liquids
i Bunsen burner
D
i mixtures of chemicals, such as coloured dyes
2 Draw a neat, labelled diagram for each separation method to show how the apparatus should be used.
[ knowledge, revision ]
7Hd/4 Separating mixtures 3
This particle diagram shows why filtering will separate sand from water, but will not separate dissolved salt from the water. You can use similar diagrams to explain how other ways of separating mixtures work.
1 Evaporation can be used to separate a liquid and a dissolved solid. Draw a labelled particle diagram to explain what happens when you heat a solution.
2 What is the difference between evaporation and distillation?
3 Chromatography can separate different coloured particles that are dissolved in a liquid. Chromatography works because the particles that make up different coloured substances are usually different sizes. Draw a particle diagram to show what happens in chromatography.
7Hd/5 Who scraped the gatepost?
Police were called to 10 Manor Road because there had been a burglary. There were some bits of red paint on the gatepost, and the police suspect that the robbers' car or van scraped against the gatepost when they were making their getaway.
A forensic science laboratory was asked to find out what make of car the burglars had used. Different car manufacturers use different mixtures of colours in their paint. The scientists used chromatography to find out the make of the getaway vehicle.
These are the results of the tests:
1 The scientists did not use water as a solvent when they carried out their tests. Why not?
2 Which manufacturer (or manufacturers) used one pure colour in their red paint?
3 Which manufacturer (or manufacturers) used a mixture of only two colours?
4 Which manufacturer (or manufacturers) used a mixture of three colours?
5 Which manufacturer uses the same paint as the paint from the gatepost?
The chromatography test does not prove that the getaway vehicle was made by the manufacturer in your answer to question 5. Post Office vans are red, so the marks could have been made when a parcel was delivered.
6 How could you show that the paint did not come from a Post Office van?
7 If the police found a vehicle that they suspected had been used in the burglary, what could they check to see if they were right?
[ knowledge, considering ]
7Hd/6 More chromatography
The chromatogram shown below is designed to see if you can analyse the results from a complex chromatogram. Look at the diagram carefully, and then answer the questions which follow. The 'standard' shown in the first column of the chromatogram contains all of the chemicals which are found in the 'tested samples'. The solvent used for this experiment was water.
1 Which of the tested samples were pure (contained only one substance)?
2 Which of the tested samples were mixtures (contained more than one substance)?
3 Name the substances contained in sample B.
4 Name the substances contained in sample D.
5 Which chemical in the 'standard' sample is the most soluble in water?
6 Which chemical in the 'standard' sample is the least soluble in water?
7 Explain your answers to questions 5 and 6.
8 Which chemicals from the 'standard' sample did not appear in any of the 'tested' samples? Explain your answer.
9 Why do some chemicals appear higher up the chromatogram than others?
7Hd/7 Forensic evidence
In 1984, Professor Alec Jeffreys of Leicester University invented a new method to identify a suspect in police investigations. Criminals often leave hairs or sweat or blood at the scene of a crime. Cells in our bodies contain a chemical called DNA, and scientists can use a method known as 'DNA fingerprinting' to compare DNA from a suspect with DNA from materials left at the scene of a crime. The chemicals found at the scene of the crime could have come from the body of the suspect or they might have come from someone else who has yet to be found.
The technique can be used to identify people who were at the scene of a crime. DNA fingerprinting is a type of chromatography.
The diagram above shows the result for several suspects.
Remember that the pattern from the suspect must be the same as the pattern from the scene of the crime if the suspect was the person who left the evidence.
Look at the pattern very carefully and answer the following questions.
1 Which suspect, Person A, B or C, was the one who left the chemicals at the scene of the crime?
2 What does this tell you about the other two suspects? Explain how you know this.
3 Do you know who committed the crime? Explain your answer.
4 Research: find out more about genetic fingerprinting and the use of chromatography to identify chemicals found at the scene of a crime.
[ knowledge, research ]
7He/1 Temperature and solubility 1
Does the temperature affect the solubility?
- Beaker
- Spatula
- Salt
- Thermometer
- Tripod and gauze
- Heatproof mat
Wear eye protection.
Fill in the gaps in these sentences, using words from the box. You may need to use some words more than once.
I am going to find out how much ___________________ dissolves in water at different
temperatures.
I will put 20cm3 of water in a ___________________ . I will measure the temperature using a
___________________ , and write it in the table.
I will add a spatula of salt and stir it until it has ___________________ .
I will keep adding more ___________________ and stirring it until no more will dissolve. I will
write down the number of ___________________ of salt I have added.
I will pour the salty water down the ___________________ , and put some clean water into the
beaker. I will make it a fair test by using the ___________________ amount of water. I will heat the
water to 40°C, and find out how much salt dissolves in it.
I will ___________________ the experiment at 60°C and 80°C.
beaker dissolved repeat salt same sink spatulas thermometer
Temperature (ºC)
Number of spatulas of salt
40
60
80
Considering your results/conclusions
___________________ (more/less) salt dissolves in water if the water is hot.
Is there any way you could have made your investigation better?
[ observing, considering, evaluating ]
7He/2 Temperature and solubility 2
- Boiling tube
- Measuring cylinder
- Copper sulphate crystals
- Glass rod
1 Add 3 g of copper sulphate to 10 cm3 of water in a boiling tube.
2 Heat the water, stirring gently all the time, until all the salt has dissolved.
3 Turn off the Bunsen burner, and let the water cool down. Watch it carefully, and write down the temperature when you first see crystals of salt appearing.
4 The solubility of copper sulphate is 30 g per 100 cm3 water at this temperature (you only used 10 cm3 of water, which has a mass of 10 g, so you multiply the mass you used by 10 to find the solubility).
5 Repeat the experiment for 4 g, 5 g, 6 g and 7 g of copper sulphate.
1 Draw a table to record your results.
2 Plot a graph to show your results. Use axes like this:
Think carefully when you are drawing your graph - the points will not be evenly spread out along the temperature axis.
3 How does the solubility of copper sulphate change with temperature?
4 How could you improve your investigation if you had time to do it again?
[ observing, presenting, considering, evaluating ]
7He/3 Separating mixtures cards
Cards 1 to 5 have the names of different ways of separating mixtures.
Cards A to J explain why the different methods work - but they are not all correct!
Cut out the cards. Match up each name card with a correct explanation card, and stick the correct cards into your book.
1 Dissolving
2 Evaporating
3 Filtering
4 Distilling
5 Chromatography
A One liquid has a higher boiling point than the other, so it evaporates first.
B The liquid evaporates and leaves the solid behind.
C Particles of the dissolved solid get stuck in the filter paper, and the solvent passes through.
D The solute (the solid) breaks up into tiny particles that mix with the particles of the solvent (the liquid) to make a solution. The solute is still all there, so the mass of the solution is the same as the mass of the solute and solvent added together.
E The solid evaporates and leaves the liquid behind.
F Solvent travels up the paper, and different soluble substances in a mixture get carried along at different speeds so they spread out.
G One liquid has a lower boiling point than the other, so it evaporates first.
H Solvent travels up the paper, and different insoluble substances in a mixture get carried along at different speeds so they spread out.
I Undissolved particles are too big to go through the tiny gaps in the filter paper, so they get trapped. The liquid and any dissolved solids go through the filter paper.
J The solute (the solid) breaks up into tiny particles that mix with the particles of the solvent (the liquid) to make a solution. You cannot see the solute any more, so the mass of the solution is the same as the mass of the solvent you used.
7He/4 How much will dissolve? 1
The table shows how much potassium nitrate (a type of fertiliser) and potassium chloride (the main ingredient in ('Lo-Salt') dissolve in water at different temperatures. The numbers tell you how many grams of solute dissolve in 100 cm3 water.
Temperature (°C)
Solubility of potassium nitrate
Solubility of potassium chloride
10
20
32
30
35
44
36
38
50
78
100
42
1 On the graph axes, plot a graph of these results.
- Choose a different colour for each solid, and show these in a key.
- Plot the points on the graph, and join them with a smooth line.
2 Use your graph or the table to help you answer the questions. Choose the correct words or numbers from the brackets.
a When the temperature goes up, the mass of solid that dissolves __________________ .
(goes up/ goes down/stays the same)
b At 10 °C, more potassium ____________________ (chloride/nitrate) dissolves.
c At 40 °C, more potassium ____________________ (chloride/nitrate) dissolves.
d At 55 °C, you would expect __________ (31/36/41/48) grams of potassium chloride
to dissolve.
e To get 70 grams of potassium nitrate to dissolve, you would need to heat
the water to about __________ degrees. (25/35/45/55)
[ numeracy, presenting, observing ]
7H Summary Sheets
Solutions
Some solids dissolve in water to make a solution. These solids are soluble. A solution is made from a solute (solid) and a solvent (liquid). When a solution is formed, the liquid is always clear (transparent).
Solids that do not dissolve are insoluble. When an insoluble solid is mixed with water, the water goes cloudy. Sometimes the solid will sink to the bottom of the water.
The total mass of a solution equals the mass of solvent added to the mass of solute.
Water is the most common solvent. It is easily available, cheap, and dissolves a lot of different solutes.
Other liquids (e.g. white spirit, ethanol) can also be used as solvents. Solutes which are insoluble in water may dissolve in other solvents.
If you keep adding solutes to a solvent, you will get to a point where no more will dissolve. A saturated solution cannot dissolve any more solute. More solid will dissolve if you add more solvent (e.g. water) or increase the temperature.
Mixtures can be separated using different methods:
Filtering (Filtration)
Solid particles which do not dissolve from the liquid they are in
- Tea leaves from a cup of tea
- Sand from a mixture of sand and water
Evaporation
Dissolved substances from a solution
- Salt from salt solution
Distillation (Evaporation followed by condensation)
The liquid from the dissolved solid in a solution or one liquid from a mixture of liquids
- Water from salt solution
- Alcohol from a mixture of alcohol and water
Chromatography
The colours can be separated from a mixture of colours
- The colours found in ink
- The food colourings found in fruit juice
7H Target Sheet
Topic
Targets
Before the unit
I have learned this
I have revised this
7Ha
Know what a mixture is.
Know the meaning of the words dissolve, soluble, insoluble.
Know the meaning of the words solution, solvent, solute.
Know that liquids and dissolved chemicals can go through filter paper.
7Hb
Know why most water has chemicals dissolved in it.
Know how to separate a dissolved solid from a liquid.
Know how to get salt from sea water.
Know how salt can be obtained from rock salt.
7Hc
Know what pure water is.
Know how to separate a liquid from anything dissolved in it.
Know what distillation is.
Know some uses of distillation.
7Hd
Know what chromatography is.
Know how to make a chromatogram.
Know what the results of a chromatogram mean.
Know some uses of chromatography.
7He
Know what a saturated solution is.
Know how to tell if a solution is saturated.
Know how the temperature affects the amount of solute in a saturated solution.
Know what solubility means.
7H Word Sheets
Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.
7Ha - The solution is clear/Melting away
Word
Pronunciation
Meaning
dissolving
diss-olv-ing
When a solid splits up and mixes with a liquid to make a solution.
filtering
Separating things that have not dissolved from a liquid. The liquid is passed through a filter to do this.
insoluble
A solid that will not dissolve.
mixture
A lot of different things jumbled up together.
soluble
sol-you-bull
A solid that can dissolve in a liquid. Salt is soluble in water.
solute
The solid that has dissolved in a liquid to make a solution.
solution
sol-oo-shun
When a solid has dissolved in a liquid.
solvent
The liquid that has dissolved a solid to make a solution.
transparent
Another word for see-through.
7Hb - Salt of the Earth
brine
A solution of common salt and water.
common salt
A chemical we use to make things taste 'salty'.
evaporation
ev-app-or-ay-shun
A liquid turning into a gas.
salts
Chemicals from rocks that have dissolved in water.
7Hc - Still water
condensing
A gas turning into a liquid.
distillation
dist-till-ay-shun
The process of separating a liquid from a solution by evaporating the liquid and then condensing it.
pure
A substance that does not have anything else in it.
steam
Water as a gas. Also called water vapour.
still
The apparatus used for distillation.
water vapour
vay-per
Water as a gas. Also called steam.
7Hd - Dyeing for juice
chromatogram
krow-mat-O-gram
The dried piece of paper produced by chromatography.
chromatography
krow-mat-og-graph-ee
Separating dissolved solids from one another. The solids are usually coloured.
7He - A soluble problem/Things are hotting up
saturated
A solution that contains as much dissolved solid as it possibly can.
solubility
sol-you-bill-ity
The amount of a solid that will dissolve in 100g of a liquid.
variable
vair-ri-able
A factor in an experiment that can change.