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Particles Lesson 1: How can the particle model explain the properties of substances? Particles Ancient Greece: Democritus, a Greek philosopher sits on the beach watching the waves move against the sand. He notices that the tiny sand grains flow in and out as the waves flow over them. He thinks ‘If the grains of sand can flow like water then maybe the water is also made of tiny grains?’ Over time he names these tiny uncuttable and invisible particles atoms, from the Greek atomos meaning uncuttable. He states that: Everything is made of atoms There is empty space between atoms Atoms are indestructible Atoms always move We often use the word particles to describe the states of matter, this is because sometimes something is made of single atoms, but other times they are made of many atoms joined together. Particles are a simplified model that makes it easier for us to explain the properties of matter. All particles are drawn as simple spheres or circles. Substance How it is drawn as a particle What it really looks like Helium Sugar The 3 states of matter All matter is broken up into 3 states. There are solid, liquid and gas. All substances can exist as these states, depending on their temperature, for example water is a solid below 0 o C, a liquid from 0-100 o C and a gas above 100 o C. Below is a diagram of the 3 states of matter Different states of matter have different properties. A property is a characteristic that is typical for that object. For example, some of the

Transcript of reflectionsinscience.files.wordpress.com  · Web viewWe often use the word particles to describe...

ParticlesLesson 1: How can the particle model explain the properties of substances?

ParticlesAncient Greece: Democritus, a Greek philosopher sits on the beach watching the waves move against the sand. He notices that the tiny sand grains flow in and out as the waves flow over them. He thinks ‘If the grains of sand can flow like water then maybe the water is also made of tiny grains?’Over time he names these tiny uncuttable and invisible particles atoms, from the Greek atomos meaning uncuttable. He states that:

Everything is made of atoms There is empty space between atoms Atoms are indestructible Atoms always move

We often use the word particles to describe the states of matter, this is because sometimes something is made of single atoms, but other times they are made of many atoms joined together. Particles are a simplified model that makes it easier for us to explain the properties of matter.All particles are drawn as simple spheres or circles.Substance How it is drawn as a

particleWhat it really looks like

Helium

Sugar

The 3 states of matterAll matter is broken up into 3 states. There are solid, liquid and gas. All substances can exist as these states, depending on their temperature, for example water is a solid below 0oC, a liquid from 0-100oC and a gas above 100oC. Below is a diagram of the 3 states of

matterDifferent states of matter have different properties. A property is a characteristic that is typical for that object. For example, some of the properties of good students are: organised, hardworking, bringing the correct equipment, being on time to lessons.Use your knowledge organiser to summarise the properties of solids liquids and gases below by writing ‘yes’ or ‘no’ in each box.property Solid Liquid GasDoes it have a fixed shape?

Does it have a fixed volume?Can it be compressed?Can it flow?

The properties of matter can be explained by knowing how the particles are arranged and how they move (known as kinetic theory) States How are the particles

arranged?How do they move?

Solid Particles are touching Particles are in neat rows Particles are held together by

strong forces of attraction

Particles vibrate in fixed positions

Liquid Particles are touching Particles are randomly

arranged Particles are held together by

weak forces of attraction

Particles can move freely and slide past each other

Gas Particles are not touching Particles are spread apart

randomly Particles have very weak

forces of attraction so are not held together

Particles are moving very fast bouncing off each other and the container.

1. What name did Democritus give the tiny units of matter?2. What were his 4 rules for atoms?3. Why do we talk about particles instead of atoms when explaining the states of

matter?4. Describe the arrangement of particles in a solid5. Describe the arrangement of particles in a liquid6. Describe the arrangement of particles in a gas7. Describe the motion of particles in a solid, liquid and gas8. Fluids are substances that can flow and be poured. Which two states of matter are

fluids?9. What state is oxygen in the picture below? Draw how its particles would be at

room temperature.

10. Complete the refutation paragraph below:Some people think that liquids can be compressed. They are wrong. Liquids cannot be compressed because……

11. Look at the diagram, what will happen when each piston is pushed?

12. A Child is playing with a bucket of sand. She pours the sand into a pile. Her father says “look the sand is flowing it must be a liquid.” Explain why the father is wrong.

13. A chocolate bunny is taken from the fridge and left out on a sunny windowsill. As it heats up it begins to change shape. Explain, using particles, why it had a fixed shape in the fridge, but began to change shape once it got hot.

Lesson 2How can the particle model explain diffusion?

If someone sprays an aerosol in a room the scent spreads around the room. It is smelt by the people nearest to it first and those furthest away last. The people

nearest also smell a stronger scent that those further away. This happens because the scent particles diffuse. Diffusion is the movement of a substance from an area of high concentration to and area of low concentration. Concentration is defined as the number of particles in a fixed area.

The reason diffusion can happen is because of kinetic theory.Kinetic theory is the idea that all particles are moving constantly. It also states that the particles solids, liquids and gases move differently.Because all particles can move that means that all particles can undergo diffusion. The rate of diffusion is linked to how fast and easily the particles can move. Below are 3 examples of how diffusion can occur in solids, liquids and gases.

Diffusion in solids Because solid particle only vibrate and are held together by strong bonds diffusion happens very slowly.

14. Potassium permanganate/agar jelly demo: Make notes about what you observe on the diagram below

High concentration Low concentration (less particles)

Low concentration (more area)

Diffusion in liquidsBecause the particles of a liquid can move past each other diffusion in a liquid is faster than a solid

15. Lead nitrate/potassium iodide practical: Make notes about what you observe on the diagram below

Diffusion in gasesIn gases the particles move freely and with a lot of energy.

16. Hydrochloric acid/Ammonia demo: Make notes about what you observe on the diagram below

How does temperature affect the rate of diffusion?

17. Conclusion: What happened and why?

The potassium permanganate in cold beaker………

Lead Nitrate

Potassium Iodide

Concentrated hydrochloric acid

Concentrated Ammonia

Equipment list:

2 × 250 cm3 beakers 100 cm3 ice cold water in one beaker 100 cm3hot water (40 °C) in one beaker Potassium permanganate crystals

Method:

1. Fill 1 beaker with 100cm3 hot water2. Fill the other beaker with 100cm3 ice cold water3. Put both beakers with their water in them side by

side.4. Use the forceps to add one crystal of potassium

permanganate to both beakers, at the same time

Whereas the potassium permanganate in the hot water……This was because………..

18. Answer the following questions in your booksa) Arrange the states of matter in order from least kinetic energy to most kinetic

energyb) Diffusion happens in all matter. Is this sentence true or false?c) A brick is put in a freezer. Are its particles still vibrating?d) Why is diffusion faster in gases than liquids?e) What is a fluid? Which two states are fluids?f) Steven says “Diffusion is faster in cold water as its easier for the particles to

move through water particles.” Is Steven correct? Give a reason.g) Complete the following sentence:

Some people think that diffusion can’t happen in solids because they don’t move. They are wrong. In fact……………………..However, diffusion is faster in liquids because…………

h) Someone is frying bacon in the food tech classroom down the corridor and around the corner from the science lab. Use particle and kinetic theory to explain how you can smell the bacon cooking whilst sat at your desk in science.

Lesson 3How can the particle model explain changes in state?

When we heat particles they move faster. This is because the energy in their kinetic store increases. As they move more the particles begin to separate. This increases the substances volume and it expands.Particles are held together by attractive forces. To change state from a solid to a liquid you need to increase the kinetic energy store of the particles enough to allow the particles to weaken those bonds. This allows the particles to be able to slide past each other and behave like a liquid. To increase the kinetic energy store of particles you need to heat them. This is called melting. If we continue heating the liquid the kinetic energy store increases even more. The particles in the liquid begin to move faster and faster. The attractive forces get weaker and weaker until finally the particles break free and can escape. They begin to bounce around the room randomly hitting the walls, ceiling and floor. The liquid has now turned into a gas. This is called evaporation (or boiling). If you reduce the thermal store, by cooling the particles, they move slower. As they slow the attractive forces get stronger and the particles become more attracted to each other. Eventually these forces will hold the particles together. The gas will have turned back into a liquid. This is called condensation. If we further reduce the thermal store the cooling particles become even more attracted each other and get fixed in place. They are now a solid. This is called freezing (or solidification).Some solid particles have very weak bonds. This means that once the particles get a small amount of energy in their kinetic store, they skip the liquid state and jump straight into a gas state. This is called sublimation. The opposite is also true with gases turning straight into solids. This is called deposition. Carbon Dioxide is a common example of these changes.

19. Complete the diagram below to summarise all the changes of state.

20. Complete the questions belowa. Which state of matter has the strongest attractive forces between the

particles?b. Which state of matter has the most energy in its kinetic energy store? c. What has to be broken for a liquid to turn into a gas?d. Circle the correct answer: When you heat the particles of a solid they:

grow bigger move faster spread apart

Investigating heating and cooling curves

Substances melt and boil at specific temperatures. The best example is water which has a melting point of 0oC and a boiling point of 100oC. Room temperature is close to 20oC so water is a liquid at room temperature.

These temperatures are different for each substance because the size of their particles and the attractive forces between them are different. We can investigate the boiling and melting points experimentally using equipment shown below.

If we record the temperature at regular intervals, we can build up a picture of what happens to the temperature as the substance is heated or cooled.Some example results are below

Time (min) Temperature (ºC)

0 321 342 363 394 425 426 427 428 459 48

10 5111 5412 5713 6014 65

21.a) Plot a graph with temperature (oC) on the y axis and time (min) on the x axisb) Name the piece of equipment that was used to take the temperaturec) The melting point of the substance was 42oC. Look at your graph and describe

what happens to the temperature when it reaches the melting point.d) The boiling point of the substance was 174oC. What would happen to the graph

if it continued up past 174oC?22. Ethanol has a melting point of -115°C and a boiling point of 78°C.

What state is ethanol at room temperature? ________________________

23. Argon has a melting point of -189°C and a boiling point of -186°C.

What state is argon at room temperature? ________________________

20°C

20°C

Salol

Explaining what happens at the melting and boiling pointAnnotate the diagram below as your teacher explains why the graph changes shape.

24. Look at the graph below for a cooling curve of naphthalene gas

a) At what temperature does the naphthalene gas turn into a liquid?b) What is the boiling point of naphthalene?c) What is happening to the kinetic energy store of the particles at 80oC?d) What is happening to the attractive forces between the particles at 80oC?

Lesson 4

How can a gas inflate a balloon?

When you want to inflate a balloon what do you do? If you blow into it the rubber will stretch, but what is creating the force needed to stretch the rubber? What about inflating tyres, do they work the same?All the questions above and many more can be explained by using particle and kinetic theory. The particles in a gas have a large amount of energy in the kinetic store so they move very quickly. They randomly hit the sides of the contained they are in, eg the balloon. This impact creates a small force. As there are a huge number of particles these tiny forces add up. This is what we call air pressure. When we inflate a balloon, we are adding more air particles. So, there will be more collisions and the force of the air pressure will increase. The pressure gets large enough to overcome the tension and stretch the rubber and the balloon expands. Another way to increase the pressure is to keep the number of particles the same but increase their kinetic energy store. If we heat the particles, they will begin to move much faster. This means they will hit the container with much more force so the air pressure will increase. Below is the apparatus of the exploding can demonstrating this fact.

25. The exploding can a) What did you observe happen as the can was

heated?b) What has happened to the number of air particle

in the can?c) What has happened to the kinetic energy store

of the particles in the can?

26. Complete the questions below in your exercise booka) Describe what gas pressure is. b) What happens to gas pressure as the temperature increases?c) Draw and complete the particle model diagram sequence to show how the

particle arrangement changes during the exploding can experiment.(the size of the arrow indicates how much energy a particle is moving with) Start During As it explodes

d) Use your diagrams and the keywords shown below, to explain why the can exploded when it was heated:Collisions/collide; particles; container; kinetic energy

27. Aerosol cans like deodorant and hairsprays contain the liquid and a gas, under pressure. When the top is pressed, the pressure of the gas pushes the liquid out of the can as an aerosol stream. They often contain the following warnings:a) Explain why it is necessary to ‘Protect

from sunlight and do not expose to temperatures exceeding 50°C’

b) Explain, in terms of particles, why other people in the room can smell the deodorant once it has been sprayed

28. The picture shows a hot air balloon. a) Explain, in terms of particles, what happens inside the balloon

when the operator lights the burner.b) Suggest why the hot air balloon does not explode

Lesson 5What happens to salt when it dissolves?

When you add salt to water it appears the salt vanishes! You can explain what happens using particle theory. Salt dissolves because it is soluble. Sand is an example of an insoluble substance, one that does not dissolve. When a soluble substance (also known as a solute) dissolves in liquid (also known as a solvent) they form a solution. This is summarised below:

The conservation of massThe conservation of mass is an important rule for all chemical and physical processes. The conservation of mass states:

This tells us that in a physical or chemical change the particles are never destroyed or made.Investigation into the conservation of mass for a solution.

You will make a salt solution by mixing some salt and water together. You will measure the mass of the salt and the mass of water before mixing

them.I predict that ……….. This will happen because ………….

Method 1. Measure 50cm3 of water using a measuring cylinder.2. Pour the water into an empty beaker, measure the mass of the beaker + water.

Record the mass into your results table.

+

Water (solvent) -Random -Moving -Medium

+ Salt (solute)

Salt solution -Salt particles fit in the gaps between the water particles. -This is why the salt is soluble

The mass before a change is equal to the mass after

3. Measure approximately 2g of salt using a balance. Record the exact mass of the salt into your results table.

4. Add the salt to the water and stir it using a stirring rod.5. Once the salt has dissolved, measure the mass of the beaker + solution and

record into your results table.6. What has happened to the mass?

Mass of beaker + water (g)

Mass of salt (g) Mass of beaker + solution (g)

Change in mass (g)

My Results:

Group no.

Mass of beaker + water (g) Mass of salt (g) Mass of beaker + solution (g)

12

34

56

78

910

Class results:

Reproducibility: Results which show the same pattern when completed separately are said to be reproducible.

29. Answer the questions belowa) Write a sentence to say whether your prediction was correct.b) Describe what happened to the mass of the water, once you dissolved the salt in

it.c) Write a formula to describe how to calculate the mass of a solution.d) Were your results reproducible? How do you know this?e) Check and amend the particle diagram below to make sure we have obeyed the

‘conservation of mass’. Explain any changes that you make

30. Prior knowledge questions

a) What is an atom?b) Describe the particle arrangement in a solid

+

c) Copper has a melting point of 1085°C and a boiling point of 2580°C. What state is copper at room temperature?

d) What do we call the process where a solid turns directly into a gas?e) What happens to the line on a cooling curve when it reaches a substances

freezing point?f) Adam is telling a friend “when I pour my drink on the table it spreads out

so its volume gets bigger” is he right or wrong? Explain whyLesson 6 What is a mixture and how do we separate them into pure substances?

A pure substance is made of only one thing with nothing else added to it. Sulfur is a yellow solid and it is pure. Iron is also a pure substance. If we mix them they become a mixture of Iron and Sulfur. A mixture is more or one substance that are together but not chemically bonded

Pure substances have a very specific melting and boiling point. For example, pure iron melts at 1530oC. Mixtures melt at lower temperatures.How to separate mixturesDepending on the states of matter that are mixed they need different techniques to separate them.Our example above is easy because Iron is magnetic so we can use a magnet. But often we need to use more complicated methods.Separation technique

Mixture to separate Example

Filtering An insoluble solid and a liquid Sand and waterSeparating by hand

Two solids Smarties and sugar

Using a magnet A magnetic substance from a non-magnetic substance

Iron nails and sand

Evaporation A soluble solid (solute) from a liquid (solvent)

Salt and water

Distillation Two liquids with different boiling points Ink and waterChromatography Two or more soluble substances Food colourings in a sweet

31. Look at the diagrams below and label each as pure or impure

Pure Iron Pure SulfurA mixture of iron and sulfur

32. Label the diagrams with the correct technique. Label the equipment with their correct names as you are shown each set up.

33. Answer the questions below in you exercise booka) Define a pure substanceb) Define a mixturec) Tap water naturally has minerals dissolved in it. Is it a pure substance? Why? d) Describe the arrangement and motion of the particles in a bar of pure Iron. (Note:

include at least 9 particles)34. Bill has bought a wedding ring for his fiancé. The jeweller told him it was pure

gold but the ticket says it contains 13% copper and the rest is gold. a) Is it a pure substance or a mixture? Why? b) What percentage of gold is in Bill’s ring?c) Suggest what the copper would do to the appearance of the ring?d) Pure gold has a melting point of 1064oC. Will the melting point of Bills ring be

higher or lower than 1064 oCLesson 7How can we get salt for our chips from rock?

We all use salt for a variety of purposes. Salt naturally is dug out the ground as rock salt. Rock salt is a mixture of salt crystals and rock. It is used to grit the roads when icy. If we want to use salt on our food we need to first purify the rock salt.

To separate the salt from the rock salt we need to think carefully about the properties of the rock and the salt. If we can find differences in their properties then we can plan a process to separate them.Hints: Are the rock and salt both soluble?Is the salt stuck inside the rock salt granules?

How to separate salt from rock salt.

Use the pictures below to help you write a method for the separation of salt from rock salt.HINT: make sure you use correct sentence starters to show the progress eg Firstly…next….then…..finally

Rock salt practical results tableMass of impure rock salt (g) AMass of empty evaporating basin (g) BMass of salt and evaporating basin (g) CMass of salt (g) C-B

Lesson 8How can we tell if we have been successful in an experiment?

When we look back at an experiment, we complete an evaluation. An evaluation looks at the results and tried to find out if we were successful. Things an evaluation might think about are:

Did we get the right results? What were some of the things that might have gone wrong? What might we do differently next time to improve the experiment?

When looking at or experiment we can use the data in the results table above to calculate the percentage by mass of the salt in the original rock salt. Because we all used the same rocksalt sample and the same procedure we should be able to compare our results and check reproducibility.

The percentage of salt you obtained from the original rock salt sample can be calculate like this:

massof clean salttotalmassof sample

×100

Worked example: If you got 5.6g of clean salt and the mass of your original sample was 13.8g:

5.613.8

×100=40.58%

Rounded to the nearest whole number = 41% Class modelled example:Suppose that I was able to extract 27g of salt from a salt-water solution with a mass of 200g. What percentage of the salt solution was salt?

Independent practice: answer the following questions in your exercise book35. Suppose that I was able to extract 15g of pure salt from a starting sample with a

total mass of 38g. What percentage is this?36. If 49g of rock salt produces 12g of pure salt, what was the percentage of salt in

the rock salt?37. If I remove 222g of impurities from 250g rock salt, what percentage salt was in

the rock salt?Give your answers to the nearest whole number

Evaluating the rock salt practicalThings to consider:

• Was your salt ‘clean’ enough to put on chips?• If not, where might you have got contamination?

• Was your percentage of salt obtained approximately the same as other people in the class?

• Look at your filter paper – anything to note there?• Where else might you have lost some salt? • What could you do to improve the method?

38. Write an evaluation of your won rock salt practical using the sentence starters to help you

My pure salt looked….This tells me……The percentage of salt in my sample was…..This was …………….compared to other groupsI think we might have lost some salt during………To improve this experiment we could……….Lesson 9How can we separate ink and water?

Aim/

introduction:

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..………………………………………………………………………………………………………………………………………Method

1. Pour the ink and water mix into a conical flask and add some anti bumping granules2. Clamp the neck of the flask with a clamp and stand.3. Add a bung and delivery tube to the conical flask and insert the delivery tube into a test tube. 4. Stand the test tube in a beaker of cold water.5. Heat the ink and water mix gently, removing the heat if the mixture boils too vigorously.

Risk assessment: Hazard Risk Safety

Hot equipment

Open flames

Key Stage 3 Required Practical:

Distillation of ink and water

Boiling liquids

Diagram 39. Add labels to your diagram, using a pencil and a ruler to draw the lines

40. Describe what happened

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

41. What was in the test tube at the end of the experiment?…………………………………………………………………………………………………………………………………………………

42. Below is a diagram showing an improved method for separating the two liquids. Add labels to the diagram.

Bunsen, ink and water mix, water, beaker, condenser, water in, water out, thermometer, round bottom flask

Key words: Boil, evaporate, condense, cool

43. Why is this equipment better than the equipment you used?44. Why is the water connected so that it flows in at the bottom and out of the top?45. What reading should be on the thermometer during the experiment if you only

want to collect water?

Lesson 10 How can we separate a mixture of soluble substances?

Sometimes we have a mixture of substances that all dissolve in water. This is often the case for forensic scientists. They need to decide what ink is used for a ransom note, what paint was in graffiti or which drugs were in an unlabelled pill. All of these can be found by using chromatography. Chromatography works because although all the substances in the mixture dissolve, smaller molecules tend to dissolve easier and move faster. The inks are placed on the stationary phase, often a piece of paper. The stationary phase has its end placed into a small amount of solvent, often water, called the mobile phase. As the water soaks up the paper the dyes spread out. The smaller dyes move faster so are near the top of the paper sooner than the heavier dyes. This means that when the mobile phase reaches the top of the stationary phase the dyes have spread out. People often imagine it like running a race through an obstacle course. One of the key things about chromatography is that if two dyes move the same distance then they must be made of the same thing. This is also used by food scientists to check the colourings used in foods are safe to eat. Once finished the paper is removed and dried. It is called a chromatogram.

46. Label the diagram with the important information about chromatography

Chromatography practical: Method1. Using a pencil and ruler, draw a baseline 2cm from the bottom of the paper

(stationary phase).

2. Put a dot of the colour on the middle of the baseline.

3. Measure 10ml of water (solvent) with the measuring cylinder and pour into the 100ml beaker. (The water level must be below the baseline.)

4. Stick the top of the paper onto a pencil5. Place the paper into the beaker so that the water just touches the bottom of the

paper. (The pencil should rest over the top of the beaker, keeping the paper steady and in place)

REMEMBER:

DO NOT let the paper bend so that the line and colours go into the waterDO NOT let any part of the paper touch the side of the beaker.

47. Using a pencil and a ruler, draw a diagram of your experiment set up. You should label it fully.Labels: Paper; stationary phase; sample spot; solute; baseline; solvent; water; pencil; beaker

48. Underneath your diagram, explain:a) Why the baseline was drawn in pencilb) Why the water(mobile phase) should not cover the colour spot c) How the mixture of solutes will be separated

49. Define the following words:a) Solubleb) Solventc) Soluted) Stationary phasee) Mobile phase

50. Look at the chromatogram on the right:a) How many different colours are in X?b) What colours are they?c) Which colour was the most soluble?

51. Look at the chromatogram below:a) How many inks in Z?b) Which pen was the same as Z?c) How do you know?d) In your book draw a particle diagram for

the solution of mixture 1(Hint 1: use different colours for each ink in the mixture)(Hint 2: remember it is dissolved in water)

Lesson 11

How can I remove graffiti from my desk?

Permanent markers, like sharpies, are waterproof. This means they are insoluble in water. They are not actually permanent though. If someone draws on a desk in marker pen we can use a different solvent to dissolve the pen. Another example is the stains on our clothes. Some stains are hard to remove with normal washing detergent and water, for example oil. To remove these, we use specially formulated stain remover. This increases the solubility of the stain in water so it will come off in the washing machine.The amount of a solute that will dissolve in a certain volume is known as its solubility, measured in g/100 cm3 . For example Sodium Chloride (table salt) has a solubility of 36g/100cm3 so 100cm3 of water at room temperature can hold 36g of Sodium Chloride.

Imagine making a cup of tea for me. “how many sugars would you like?” you ask as you pour in the boiling water. “Ten please!” I reply. What would happen as you began to add the sugar? What would happen once you got to the 5th

spoon? Would it still dissolve?

When a solute dissolves in a solvent the solute particles can be thought to fit into the gaps between the solvent particles like shown below. Once all the gaps are full the solvent cannot hold any more solute and no more will dissolve. We say this is now a saturated solution. Saturated means ‘holding as much as possible’ If you get caught in a thunderstorm your clothes can become saturated with water.

52.Answer the questions below in your exercise booka) Define solventb) Define solutec) Define solutiond) Define saturated solutione) Sinead says “A saturated solution forms when the solvent dissolves into

the gaps in the solute” is she right or worng? Give a reason.

We saw above that sodium chloride had a solubility of 36g/100cm3 in water. Different solutes have different solubilities. Potassium nitrate is another type of salt. It has a solubiltiy in water of 46g/100cm3. Look at the table below to see how changing the solvent affects the solubility.

53.Which solvent is potassium nitrate the most soluble in?

54.Which solvent is potassium nitrate the lest soluble in?

SolventSolubility of potassium nitrate (g/cm3)

Water 46

Ammonia 10.4

Acetone 0.7

Alcohol (ethanol) 3.7

55.If I wanted to dissolve 10g of potassium nitrate would I need more Ammonia or Alcohol?

56.Why does stirring help the solute to dissolve?

Investigating the solubility of various solutes in different solvents (demo)1. Place a small volume of a solvent in a boiling tube2. Add a solute, place a cork in the tube and shake.3. Observe if the solute dissolves

SoluteSolvent

Water Ethanol CyclohexaneSodium chloride

Wax

Sand

Sucrose (sugar)

57.Which solute is completely insoluble?58.What is the pattern in solubility in water compared to cyclohexane?59.Complete the sentences below

Some people think wax is insoluble. This is not true. In fact wax is……………….

Do gases dissolve? The ammonia fountain (demo)

The water in the trough has some acid in it. This turns the indicator red. When the syringe is pushed a small amount of water goes into the round flask. The ammonia gas dissolves into the water. This means there are less gas particles in the flask. This reduces the pressure inside the flask creating a vacuum. This sucks up the water and indicator from the trough. As the ammonia is an alkali the indicator changes from red to purple. Why do we use hot water for a cup of tea?Have you ever made a cup of tea with cold water? It doesn’t really work. This is because the tea is not very soluble in cold water. When we heat particles we increase their kinetic energy store and they begin to move faster. As they move faster there are more gaps between the particles. As there are more gaps more solute can dissolve in the solvent.

Below is some data from a students’ investigation into temperature and solubilityTemperature of water (_______) Mass of salt that dissolves (_____)

10 12

20 24

30 30

40 48

50 60

60.Write the units for temperature and mass in the brackets above61.Put a scale on the X axis and label it 62.Plot the data from the table on the graph below63.One of the points does not fit the pattern. Circle it.64.Draw a straight line of best fit through all the results that fit the pattern.

HEAT

Colder particles

Less kinetic energy Slow moving solvent cannot

break apart solute easily Slower vibrating solute

cannot break apart easily Only small mass dissolves

Hotter particles

More kinetic energy Fast moving solvent cannot

break apart solute easily Faster vibrating solute

cannot break apart easily larger mass dissolves

65.How does increasing the temperature affect the mass of solute that dissolves

66.Complete the sentences below:a) Heating the solvent increases the mass of solute that dissolves

because…b) Heating the solvent increases the mass of solute that dissolves but…c) Heating the solvent increases the mass of solute that dissolves so…

Interleaved questions for revision67.Which diagrams represents a pure substance? There may be more than

one. Explain your choice

A B C D68. Define an atom69.Define the conservation of mass70.Why can you separate Iron and Sulfur with a magnet but not Carbon and

Sulfur?71.Wax has a melting point of 37oC what state will it be at room temperature 72.Draw lines to match the technique shown with the correct name. Draw

only 3 lines.

0

10

20

30

40

50

60 Mass of salt dissolved (g)

73. Describe how you could use the equipment below to separate a mixture of 2 liquids – water and ethanol.

Ethanol boils at 70°C and water boils at 100°CUse these key words in your answer: liquid, gas, boil, condense, heat, cool

74.A student separated the colours in a drink and compared it with some known food colours.

a) Why was the start line drawn in pencil?b) Which two food colours were contained in drink X?c) How many food colours were present in drink Y?75.Explain how you can test to see if a

substance is pure.76.Describe a method for producing crystals

of copper sulphate from a solution of copper sulphate that has been contaminated with sand.

crysta llisa tion

filtra tion

distillation

chrom atography

B

A

filter pape r

pencil line

spo t o fdrink X

spot ofE 102

spo t o fE160

spot o fE 110

spo t o fdr ink Y

C a thy 's ch rom atogram

thermometer water out

cold water in

77.A child spills a can of cherry cola. Explain why the students near them can spell the cheyry scent sooner than the students further away, using the concept of diffusion.

78.A student tries to extract salt from rock salt. They manage to produce 14g of salt from 42g of rock salt.

a) Why did they crush the rock salt before adding water?b) Why did the filter the rock salt solution?c) How did they remover the salt from the salt solutiond) Calculate the percentage mass of salt in the rock salt. Show your

working.79.Label the graph with as much information you can. You can use diagrams

if you wish.

80.Find the mistakes in each of the sentences on the left. Write a corrected version in the box on the right

Wrong statement Correct statement

Particles in a solid are fixed in place and not moving

When you heat a solid, the particles start to vibrate

When you heat a substance the particles expand

You can separate a mixture of a liquid and an insoluble solid using a sieve

You can separate a mixture of a soluble solid and a liquid using a filter

When a solid dissolves in a solvent, the mass disappears

When an ice cube melts into water, the mass increases

You should draw the start line in pencil for chromatography because you can rub it out if you do it wrong