Matter BookletLesson 1 Particles and densityIn year 7 we learnt that particles are the building blocks of matter. We learnt that they can exist in 3 states solids, liquids and gases and that solids were denser than liquids which were denser than gases.Which weighs more – a kilogram of feathers or a kilogram of iron? They weight the same!! Which would take up more space? Density is the amount of matter a substance has in relation to its volume. It is a sign of how closely packed the particles of a substance are. But if we consider the picture to the right, we realise that this is not the whole truth. So, this topic extends on our understanding of how particles and forces interact.

1. Complete the table below to check what you recall form year 7

DensityDensity is the amount of matter (particles) in a specific volume. Particles that are close packed will have a greater mass in the same volume, increasing the density. Gold is very dense material, it has heavy particles that are closely packed. Helium has a very low density because its particles are spread apart and are very light.

The density can be calculated using the following equation:

2. Explain the following in terms of particles and density.a) Bubbles always rise to the surface b) A hot air balloon rises when the burner is turned onc) In a kettle, all the water boils even though the heat is at the base of the

kettle3. Predict whether the following will float or sink in water.

The density of water at 25°C is 1.0 g/cm3

Substance Density (g/cm3)

Float or sink?

Explain

Brick 1.9Cork 0.12Concrete 2.3Oil 0.72Lithium 0.535

4. Jan says to the class. “I think the copper penny will sink if dropped on mercury” Is she right or wrong? Explain your answer Using the data belowLiquid mercury = 13.5g/cm3 copper penny = 8.96 g/cm3

Investigating densityFollow the instructions and write your answers in the table provided:

1) Take your block to the balance2) Record its mass 3) Calculate its volume using a ruler4) Calculate its density

Material Mass (g) Volume (cm3) Density (g/cm3 )

5. Which substance had the highest mass?6. Which substance had the largest volume?

g/cm3 or

Kg/m 3

g or Kg

cm3 or m3

7. Which substance had the largest density?8. Look back at the fish tank with two bowling balls in. Paul says “One is floating and

the other is sinking because of density” Paul is right but his answer lacks detail. Explain why one floats and the other sinks. Use the words density, mass, volume, weight and upthrust in your answer

Calculating densityExample 1: Calculate the density of an object with a mass of 150g and a volume of 300cm3

1. Equation: write it outρ=m÷v

2. Values: Write out, check units are correct

ρ= ? m= 150g v= 300

3. Enter values: into equation

ρ=150 ÷ 3004. Resultρ=150 ÷ 300= 0.55. (Y)UNITS (if

needed)0.5 g/cm3

Example 2: Calculate the density of an object with a mass of 300g and a volume of 150cm3

1. Equation: write it out

ρ=2. Values: Write out, check

units are correctρ= ? m= v= 3. Enter values: into

equationρ=4. Resultρ=5. (Y)UNITS (if needed)

Example 3: Calculate the density of an object that has amass of 200g and a volume of 150cm3

E

V

E

R

Y

9. Calculate the density of a block of metal with mass 1.2g and volume 0.3cm3.10. Calculate the density of a concrete block which has a volume of 1000cm3 and a

mass of 2400g11. Calculate the density of an iron bar with a mass of 39300kg and a volume of 5 m3

(hint: make sure you give the correct unit!)12. Calculate the density of a piece of rubber that has a volume of 0.33m3and a mass

of 506kg

Calculating massExample 1: Calculate the mass of an object with a density of 0.5g/cm3 and a volume of 300cm3

1. Equation: write it outρ=m÷v

2. Values: Write out, check units are correct

ρ= 0.5 m= ? v= 300

3. Enter values: into equation

0.5 =m ÷ 3004. Result

Example 2: Calculate the mass of an object with a density of 300g/cm3 and a volume of 150cm3

1. Equation: write it outρ=

2. Values: Write out, check units are correct

ρ= m= ? v= 3. Enter values: into

equationρ=4. Resultm=

Example 3: Calculate the mass of an object that has a density of 3.5g/cm3 and a volume of 150cm3

E

V

E

R

Y

m=0.5 x 300= 1505. (Y)UNITS (if

needed)150g

5. (Y)UNITS (if needed)

13. Calculate the mass of an object that has a density of 13 g/cm3 and a volume of 39cm3

14. A chess piece has a volume of 6.75cm3 and a density of 14g/cm3. Calculate the mass. Give your answer to 2dp

15. A table has a density of 0.71g/cm3 and a volume of 21,127 cm3 calculate the mass.

16. Convert your answer above into kilograms. Give your answer to 2sf.

Calculating volumeExample 1: Calculate the volume of an object with a mass of 150g and a density of 0.5g/cm3

1. Equation: write it outρ=m÷v

2. Values: Write out, check units are correct

ρ= 0.5 m= 150g v= ?

3. Enter values: into equation

0.5=150 ÷ v4. Resultv=150 ÷ 0.5= 3005. (Y)UNITS (if

needed)300 cm3

Example 2: Calculate the volume of an object with a mass of 300g and a density of 2 g/cm3

1. Equation: write it outρ=

2. Values: Write out, check units are correct

ρ= m= v= ?3. Enter values: into

equationv=4. Resultv=5. (Y)UNITS (if needed)

Example 3: Calculate the volume of an object that has a mass of 200g and a density of 12g/cm3

E

V

E

R

Y

17. Calculate the volume of an object with a mass of 600g and a density of 2g/cm3

18. Calculate the volume of an object with a mass of 50kg and a density of 2kg/m3

19. Calculate the volume of an object with a mass of 250kg and a density of 0.5kg/m3

L2 Brownian Motion and DiffusionBrownian motion, is the random movement of particles suspended in a fluid (liquid or gas). It occurs from their collision with fast moving molecules of the fluid. Imagine standing in a room full of people who were all running in different directions and imagine how you would be knocked about the room. Your motion could be described as Brownian. This is what it is like to be a particle in a liquid or gas. Potassium

permanganate in a beaker demo20. How were the particles of potassium

permanganate arranged at the start?21. What happened as time passed?

22. What word describes the way the potassium permanganate moved through the water?

23. We didn’t stir the mixture so what provided the energy to help them spread out?This is essentially what Brownian motion is. You already know about it but didn’t know what it was called

Diffusion is the passive movement of a substance from an area of high concentration to an area of low concentration. Diffusion happens in liquids and gases because their particles move randomly from place to place. Diffusion is an important process for living things; it is how substances move in and out of cells.

25.What does passive mean? 26. Someone has sprayed Lynx Africa just inside the classroom door! a) Describe how the smell diffuses around the room, you could draw simple

diagrams to helpb) Explain why the students at the front can smell it firstc) Explain why it smell strongest near the doord) Would it spread faster or slower on a hot day? Justify your answer27. Frazer says “Diffusion is caused by Brownian motion, the particles move from an

area of low concentration to high concentration. This is an active process.” This answer is wrong. Write the correct sentence in your book.

L3 Pressure in liquids

We know that pressure is a measure of how much force is applied over a given area. We can calculate the pressure applied if we know the area and the force. If we increase the area, we decrease the pressure applied by a force. Pressure can be calculated using the following equation. (You will have to be able to arrange this and calculate any of the three factors)

33. Calculate the pressure of a knife with an area of 0.005m2 and a force of 40N.34. Calculate the pressure of a shoe with an area of 0.02m2 and a force of 1400N.35. Calculate the pressure of a car tyre with an area of 0.5m2 and a force of 14500N.36. Calculate the pressure if a car crashes into a wall with 25000N and with a front

area of 199cm2

37. A woman of mass 47.5kg on Earth stands in a pair of shoes with an area of 0.003m2. Calculate the pressure she is exerting on the ground. (Hint: First calculate her WEIGHT using weight = mass x gravity)

38. A child of mass 50.4kg on Earth lies on the bed with an area of 0.75m2. Calculate the pressure the child is exerting on the bed.

When pressure is applied to a liquid the pressure is transferred through the liquid, (remember that liquids cannot be compressed but can flow!). This means that the pressure is the same everywhere in that liquid. This is extremely useful as it means pressure (a force) can be applied anywhere that liquid comes into contact with a surface. By manipulating the size of the area, a force is applied in a liquid we can affect the size

of the force that is applied elsewhere. This is used in braking systems, hydraulic machinery and many other situations.Cartesian diverA cartesian diver is a great way of understanding the way pressure behaves on a liquid. You can make one with a straw or pen top, blu tack and a drinks bottle.

39. Use the diagrams and the keywords to explain the journey of the cartesian diver as you squeeze the side and release. Key words: Pressure, compressed, density, float, sink, water, expands, particles, space

40. Boris says “it only works if you squeeze at the top of the bottle because you need to push down with a force.” Is he correct? Give a reason for your answer

Look at the diagram of the pressure can41. Explain why the water makes the

pattern it does. Include particles and forces in your answer

Hydraulic systems take advantage of the fact that the liquids can’t be compressed. This means they will transmit any pressure they experience. Pressure is the force divided by the area so if we change the area we can drastically change the force. This can create machines which multiply the force exerted. Car breaks and power steering are good examples, as is the mechanical arm on a JCB diggerWorked exampleA hydraulic system is shown below. The master piston has an area of 0.2m2 and the slave piston has an area of 0.8m2. A force of 10N is applied at X. Calculate the force at Y.

Step Answer

1. Calculate the pressure of the piston you have complete data for

P = F ÷ A P= 10 ÷ 0.2

P = 50

2. Include units N/m2

0.2m20.8m2

3. The pressure is fully transmitted – enter this value here

50 N/m2

4. Are you trying to find force or area?

Force

5. Substitute your moment value from step 3 and the remaining value from the question into the right equationForce = Pressure x AreaArea = Force ÷ Pressure

Force = 50 x 0.8Force = 40

6. Add units 40 N

Hydraulic Machines42. What do we mean when we say that a machine is “hydraulic”?43. Fill in the gaps by crossing out the incorrect phrases:There are the four key properties of liquids that are important to remember whenlooking at hydraulic machines:

a) Liquids will always (flow to take the shape of their container/ keep the same shape) no matter what container you use.

b) If you have a fixed amount of liquid, then its volume (can change / will always stays the same) when pressure is applied to it.

c) The pressure in a fluid (acts in all directions / acts in the direction of theapplied force).

d) If a constant force acts throughout a liquid, the pressure (can vary / staysthe same) throughout the liquid.

44. Each of these properties can be explained by thinking of the way particles that

make up the fluid move and interact with each other. How?45. A mechanic wants to inspect the

bottom of a car for a leak. She tries to lift the

car using a hydraulic lift.a) On the diagram, draw and label arrows to show the direction in whicheach of the following forces act:

I. The weight of the car acting on its pistonII. The force exerted by the mechanic on her pistonIII. The hydraulic force of the liquid acting on the car’s piston

b) The area underneath the mechanic’s piston is 0.1m2, and the area underneaththe car’s piston is 10m2. If the cars mass is 1000kg, how much force does themechanic need to apply to lift it? (Hint: remember force is measured inNewtons, not kilograms!)c) If the mechanic pushes her piston down by 2 metres, by what distance is thecar lifted?46. Why do your ears pop if you swim to the bottom

of the deep end at the pool?

L4: Floating and Upthrust

Sir Isaac Newton was the first to realise that forces are always acting. When a boat is floating its weight is constantly trying to pull is under the water. Fortunately, is has a volume large enough to displace water. The water pushes upwards. This creates a force called upthrust. It will balance the weight and so there is no resultant force and the boat stays floating.

Investigating weight in waterMethod

1. Collect a newton meter, beaker and an object2. Record the weight in air3. Fill the beaker with enough water to submerge the object without it touching the

bottom.4. Submerge the object and record the weight in water.5. Repeat with other objects and record in a table of your own design in your books.

Conclusion47. What happened to the weight of the objects in water? Explain why48. What can you say about the weight of the objects that float?49. What is the trend between the objects that sink and their weight in water?

Building shipsShips like aircraft carriers and tankers are absolutely huge! They are also made of iron. Iron has a density 8g/cm3, about 8 times greater than water. So at first glance they shouldn’t float, but they do (thankfully!)The key to their buoyancy is their shape. They are in fact mainly air with broad sides that dip deep into the water. This means the upthrust created is much larger than the mass of the ship. This allows them to carry cargo.As the cargo is loaded the boat will begin to dip deeper into the water.

The problem is the water is not always the same. Differences in the salt concentration and temperature effect the amount of upthrust the water can create. Ships have a plimsoll line to show how much weight they can carry before they

risk sinking. It has markings to show different levels for different seasons and water types.

50. What is the name of the force which creates and objects weight?51. What is the name of the force which prevents a boat sinking?52. A cork is floating in a beaker, what can we say about the size of the weight and

upthrust?53. Is upthrust a contact or non-contact force?54. A leaf is floating on a pond, what is the vertical resultant force?55. Look back to the bowling balls in the first picture. In either case is there a

resultant force? Justify your answer56. A life ring is thrown into a lake. It floats. Draw a force diagram and label the forces

involved57. If a tanker moves from sea water to fresh water it needs to make sure it is

not overloaded or it will sink too low in the water. Explain why?58. Explain why it is easier to float in the swimming pool by lying on your back?59. Ice from a freezer is put in a glass of water at room temperature. The ice

floats in the water.

(i)     What does this show about the density of the ice compared to that of water?

         Circle the correct answer.

Ice is more dense than water.                                 

Ice and water have the same density.                    

Ice is less dense than water.                                  

Ice has a density of zero.                                        1 mark

(ii)     The fact that ice floats in water tells us something about the distances between the molecules. Tick the correct statement.

The molecules are further apart in ice than in water. The molecules are the same distance apart in ice and in water. The molecules are closer together in ice than in water.

60. The diagrams show cells containing and surrounded by oxygen molecules.

Oxygen can move into cells or out of cells.

 

Into which cell, A, B, C or D, will oxygen move the fastest? Explain why: 61. Complete the following sentence. “Oxygen is taken into the cell by the process

of ....”

62. Abi investigated how adding salt to water affects the way an object floats. She used the apparatus below. She used a scale inside a test-tube to measure the length of the test-tube above the water level.a) What factor did Abi change as

she carried out her investigation (the independent variable)?

Abi plotted her results on a graph

b) On the graph, circle the result which does not fit the pattern.c) Suggest one reason for this result.d) Draw a line of best fit on the graphe) What conclusion can Abi make from the data? f) Describe two ways of dealing with the anomalous point

L5: Air pressure

The earth is a magnificent world. One of the incredibly special properties of our planet is its ability to maintain an atmosphere. The atmosphere is the name we give the layer of gases which surrounds a planet. The Earth’s atmosphere is about 700km high and is made of different levels. Other planets also have atmospheres some are much denser, like Venus, whereas others are much thinner like Mars. The earth is much bigger than mars so has much more gravity. This helps attract the gas particles to the surface and helps explain why our atmosphere is much thicker.

Gases are ‘ideal’This means that all gases behave the same way. It doesn’t matter if they are oxygen, carbon dioxide or hydrogen. This is because the molecules are so small and so far apart their different sizes becomes irrelevant. This makes understanding the atmosphere much easier.Gases are fluids too – remember, they can flow. Gases have weight – caused by gravity.

Atmospheric pressureThe atmosphere exerts a pressure on us all of the time. We don’t feel it because the air in our bodies is exerting the same pressure outwards. The forces are balanced. We can use experiments to prove the existence of atmospheric pressure

Experiment Observation Explanation

Vacuum pump with marshmallows

Egg in the bottle trick

Inverted jar of water

The collapsing can

63. The diagram below represents the particles found in air.

 

(a)     Complete the following table. Use the diagram and key above to help you.

 name symbol chemical formula

argon   Ar

nitrogen   

oxygen   O2

  

 

(b)     Air is a gas at room temperature. What evidence in the diagram above shows this?

(c)     A sample of air in a balloon is cooled.Complete the sentences below using words from the box.You may use each word more than once.

    increases                 decreases                  stay the same

When the air is cooled, the volume of the air ........................................... and the mass of the air ............................................. . When the air is cooled, the density of the air ............................................. .

(d)     In 1902, the scientist Carl von Linde cooled air to produce liquid oxygen.

The table below shows the melting points and boiling points of four substances that are found in air.

 substance melting point (°C) boiling point (°C)

argon –189 –186

oxygen –218 –183

nitrogen –210 –196

water 0 100

Before Linde, scientists tried to produce liquid air by cooling it to –190°C.Give a reason why liquid air was not produced.

Boiling water. Boiling water is often explained by explaining how the water particles absorb energy from the thermal store and begin to increase their kinetic store. As they move faster, they escape into the atmosphere. This is not completely true. To escape into the gas phase the water needs to overcome the air pressure pushing down on the surface of the water. If we increase the air pressure the boiling point increases. If we reduce the air pressure the boiling point drops. If you remove all the air the water will spontaneously boil at room temperature!

64. Water boils at sea level at 100oC but on the base camp of Mt Everest it is only 82oCa) Explain why the water boils at such a lower temperatureb) Calculate the percentage decrease in boiling point

65. During take off and landing on a plane peoples ears pop. Use air pressure to explain why this occurs

66. Identify if these are true or falsea) The atmosphere is mainly oxygenb) The atmosphere is denser at the bottomc) Gravity holds the atmosphere on the Earthd) Water can boil at room temperaturee) High altitude is hotter than low altitude

64. What term is given to random motion of particles because of collisions with other particles?

65. What is the equation linking force, pressure and area?66. What word means the mass of dissolved substance per unit volume?67. What word means to push into a smaller volume (e.g a gas)? 68. What is the unit for pressure?69. What word refers to rising hot air or liquids?70. A pen cap floats in a plastic lemonade bottle three-quarters full of water.

If you squeeze the bottle the pen cap sinks to the bottom.If you then let go of the bottle, the pen cap floats to the surface.

(a) When the bottle is squeezed what, if anything, happens to:I. the distance between the air molecules inside

the bottle? II. the distance between the water molecules

inside the bottle? III. the pressure of the air trapped inside the pen

cap?IV. the volume of the air trapped inside the pen

cap?

(b)     Explain why the pen cap sinks when you squeeze the bottle.

71. Karen wants to pump up her car tyre. Her pump has a piston with an area of 7 cm2. Karen pushes the handle down with a force of 175 N.

(a) What pressure does she exert on the air in the pump?

(b) The air pressure in the tyre is 27 N/cm2. What pressure would be needed in the pump in order to pump more air into the tyre?

(c) Another of Karen’s car tyres exerts a pressure of 30 N/cm2 on the road. The area of the tyre in contact with the road is 95 cm2

What is the force exerted by the tyre on the road?

72. Diagram A represents a gas in a container. The gas can be compressed by moving the piston to the right.a) (i) How can you tell that

the substance in the container is a gas?

(ii) How can you tell from the diagram that the gas is pure?

(b) The piston is moved to the right as shown in diagram B. How can you tell, from diagram B, that the pressure of the gas has increased?

(c) Diagram C shows what happened to the molecules after the gas wascompressed more.     

(i)  How can you tell that a chemical reaction happened when the gas was compressed?

(ii)  The mass of the gas in both diagrams B and C was 0.3 g.

Why did the mass of the gas not change when it was compressed?

(iii)     Complete the table below with the correct chemical formula of eachsubstance. Use the key to help you.

 

(iv)    What is the name of the substance represented by the symbol ?

73. Sue pumps up a bicycle tyre. As she does so, she notices that the pump becomes hot.

(a) Where, and how, was the energy stored before it was transferred in pumping up the tyre?

(b)  Explain how the gas molecules inside the tyre exert pressure on the walls of the tyre.

(c) The air going into the tyre was warmed up by the pumping. What effect will this have on the motion of gas molecules in the air in the tyre?

(d)  When the air in the tyre becomes hotter, the pressure rises. Give one reason, in terms of the motion of gas molecules in air, why the pressure rises.

(e) The pressure in the tyre increases as Sue forces more air into the tyre. Explain why a larger number of gas molecules increases the pressure in the tyre.

74. Some students fill an empty plastic bottle with water.The weight of the water in the bottle is 24 N and the cross-sectional area of the bottom of the bottle is 0.008 m2.

(a) Calculate the pressure of the water on the bottom of the bottle and give the unit.

(b) The students made four holes in the bottle along a vertical line.They put the bottle in a sink. They used water from a tap to keep the bottle filled to the top.

The students measured and recorded the vertical heights of the

holes above the sink.They also measured the horizontal distances the water landed away from the bottle.A pair of measurements for one of the holes is shown in the diagram.

The complete data from the experiment is shown in the table. 

HoleVertical heightin cm

Horizontal distance

in cm

J 24 15

K 18 20

L 12 30

M 6 40

 (i) Which hole is shown in the diagram?

(ii) On the diagram, draw the path of the water coming out of hole M.

Use the information in the table to help you.

(c) Suggest one problem that might arise from trying to collect data from a fifth hole with a vertical height of 1 cm above the sink.

75. The diagram below shows an empty cargo ship. It is not moving.

 

(a) The water exerts a force on the ship. In which direction does this force act?

(b) The diagram below shows the same cargo ship. This time it has a full load of cargo.

 

(i) How does the force exerted by the water on the ship change as the ship is loaded?

(ii) Why has the force exerted by the water changed?

Incorrect/poor statement Correct statement

Liquids and gases can be compressed

When you compress a gas, the particles get smaller

Diffusion is the random movement of particles

The particles in a liquid are further apart than in a solid

When solids are heated, the particles start to vibrate

When ice melts, the particles in the liquid can vibrate freely

Gas pressure is caused by the particles moving around

When water freezes, the particles stop moving