1. Solids
Chapter 12
Unit 6

2. Crystal structure

3. Metals, salts, and most minerals are made up of crystals.
Crystals have a three dimensional orderly arrangement
A crystalline latticework of atoms
This structure was first determined by X ray in 1912
German physicist Max von Laue discovered that a beam of X rays directed upon a crystal is diffracted into characteristic patterns.

4. Crystal structures are determined experimentally by X-Ray Diffraction

5. William Henry Bragg and his son William Lawrence Bragg developed a mathematical formula that showed just how X rays should scatter from the various regularly spaced atomic layers in a crystal.

6. Non crystalline Solids
Are said to be amorphous.
In an amorphous state, atoms and molecules are distributed randomly.
Examples:
Rubber, glass, and plastic
They lack an orderly, repetitive arrangement.
The particles also have some freedom to wander.

7. Rubber
The amorphous state of rubber allows it to be elastic (stretch).

8. Glass – Look at the waves on the window pane

9. density

10. Think, Pair, & Share
Is Iron heavier than wood?

11. Density 𝐷𝑒𝑛𝑠𝑖𝑡𝑦= 𝑚𝑎𝑠𝑠 𝑣𝑜𝑙𝑢𝑚𝑒
The masses of the atoms and the spacing between them determine the density of materials.
Density is a measure of the compactness of matter, how much mass occupies a given space.
𝐷𝑒𝑛𝑠𝑖𝑡𝑦= 𝑚𝑎𝑠𝑠 𝑣𝑜𝑙𝑢𝑚𝑒
Density can be expressed in terms of weight rather than mass. This is referred to as weight density.
Weight density is measured in N/ 𝑚 3

12. Elasticity

13. Elasticity
Is the property of a material wherein it changes shape when a deforming force acts upon it, and returns to its original shape when the force is removed.

14. At which length does the spring possess the greatest elastic potential energy?B C D
15.
Kern carried out an experiment to find out the number of times the key to a toy car is turned and the distance it travelled. He placed the car at the same starting point, S each time. The track which the car followed was horizontal from 200cm followed by a gentle slope starting at point T.
The results of his test were recorded in the table below:
Number of turns of the key 2 4 6 8 10
Average distance trevelled (cm) 50
100
150
200 ?
Predict the average distance (in cm) travelled by the car as it moves up the slope when Kern made 10 turns on the toy car.
220
250
300
16.
The diagram below shows a man playing golf. He has to swing both his arms to the side simultaneously to hit the ball with his golf club.
Which one of the following correctly identifies the effort, fulcrum and load?
Effort
Fulcrum
Load
(1)
Arm and Hand
Body
Golf club
(2)
Ball
(3)
(4)
Arm
17.
The experiment shown below was carried out in a dark room. A clear plastic, a tracing paper, a clear glass and a copper sheet were placed at various distances from the source of light. An opaque object was placed between the torch and material A.
When the torch was switched onm a dark shadow was seen on sheet C only.
Which one of the following shows a possible arrangement of the materials?
Clear Plastic
Tracing Paper
Clear Glass
Copper Sheet
18.
Study the diagram below carefully.
What energy conversion has caused the paper to have burn marks on the paper?
Solar energy → Light energy
Light energy → Heat energy
Heat energy → Light energy
Light energy → Chemical potential energy
19.
Study the classification chart below carefully.
Which of the above materials are wrongly classified?
Nickel, iron and silver
Iron, silver and aluminium
Nickel and frosted glass
Iron and aluminium
20.
Mei Ling used 2 simple machines to study the relationships between the load and the effort. She recorded her observation and plotted the graph below.
Match the 2 machines to the lines P and Q on the graph above. P Q
(1) A fixed pulley A movable pulley
(2) A see-saw A fishing rod
(3) A claw hammer A ramp with an angle of inclination of 80°
(4) A fixed pulley A ramp with an angle of inclination of 30°
21.
When the big gear turns one round, what will happen to the small gear?
It'll turn more rounds in the same direction.
It'll turn more rounds in the opposite direction.
It'll turn less rounds in the same direction.
It'll turn less rounds in the opposite direction.
22.
3 new batteries and a new bulb are used to form the following circuits.
Which of the above bulbs will light up?
B only
A and B only
A and C only
B, C and D only
23.
What inferences can be made based on the experiment above?
A: Condensation has taken place.
B: Heat is lost by the surrounding air to the beaker.
C: The water droplets are formed from the water in the beaker.
D: The room temperature is higher than the temperature of the water at the start of the experiment.
B and D only
A, B and D only
A, C and D only
24.
The girl below was standing in front of a mirror with a word card.
Which one of the following correctly shows the mirror image of the word "SCIENCE"?
Booklet B 1.
George set up an experiment as shown below. He filled a plastic bag with starch solution. The bag is placed into a beaker containing water with some brown iodine solution. He then left it overnight.
The next day, George observed that the starch solution in the plastic bag had turned dark blue.
a) Why did the starch solution turn dark blue and not the iodine solution?
Ans:________________________________________________________________________________
___________________________________________________________________________________.
b) Which part of the plant cell exhibits the above property mentioned in (a)?
Ans:_______________________________________________________________________________. 2.
a) In what ways are the plants that produce the above 2 groups of fruit similar?
b) The fruits of both groups above are edible and eaten by animals. However, there is a difference in the way their seeds are scattered. What is the difference? 3.
Kandy wanted to find out what type of soil was suitable for growing a balsam plant. She planted 3 balsam plants of similar size in 3 pots, X, Y and Z.
Pot X
Pot Y
Pot Z
Material of Pot Plastic Plastic Plastic
Type of Soil Clayey Garden Sandy
Amount of Soil 1500g 1000g 800g
Amount of Water (daily) 150cm3 150cm3 150cm3
a) Why was the experiment not a fair one?
b) If Kandy solved the problem in (a), which soil do you think will be best and why? 4.
The diagram below shows a working model of a human chest. A rubber sheet is stretched across the bottom of the bell jar and tied firmly in place.
a) Which parts of out respiratory system do the following parts of the model represent?
Model
Respiratory System
Glass Tube
Balloons
b) What would you observe in the ball jar when the rubber sheet at the end of the jar was pulled and then let go?
Ans:_______________________________________________________________________________ 5.
Xiao Long placed Setup A and B below in a room at 30° C for 3 weeks.
a) What is Xiao Long trying to find out the experiment?
b) Why is the process, which the prawn is undergoing, important to the environment? 6.
Yun Da set up an experiemtn as shown below.
a) State the condition which is not shown in the diagram but is necessary for the survival of the plant and animals in this experiment.
Ans:______________________________________________________________________________.
b) How does the conditions stated in (a) help the plant and animals to survive?
c) What does this experiment show about the relationship between plants and animals? 7.
In a circus show, male acrobat A performs a somersault as shown below. Acrobat A gets his energy indirectly from female acrobat B.
a) What could acrobat B do to help acrobat A perform his somersault at a greater height?
b) When acrobat B was replaced by acrobat C, it was noticed that acrobat A jumped to a greater height before coming down. Explain this observation.(Both acrobats B and C jumped from height X)
___________________________________________________________________________________ 8.
Tom conducted an experiment to find out if the magnetic strength of a bar magnet increases with its size. He hung all the 4 magnets at the same distance away from a tray of evenly spread nails.
a) What conclusions can Tom draw based on his result?
b) Based on Tom's experiment, which of the following statements are true? (Indicate the true statements with a letter 'T' in the boxes provided)
Statement
True?
(i) Magnetic force can act at a distance
(ii) Magnetism can pass through non-magnetic material
(iii) The nails are made of magnetic materials 9.
Weights were hung progressively to 2 springs P and Q to determine thei degree of elasticity. The table below shows the result of the experiment.
Weights attached (g) Length of spring P Length of spring Q 20 9 40 12 60 15 14
a) What is the original length of spring P?
b) Which spring is more elastic? How do you know?
____________________________________________________________________________________
c) What is the length of spring Q when a 50g weight is hung on it?
10.
An empty glass with a piece of tissue paper stuck to its inner surface was lowered into a basin of water vertically until it was fully submerged.
a) Draw a line to show the level of water in the glass.
b) Did the tissue paper get wet? Explain your answer.
Booklet A (Answers)
Answers B. A. C. D.
11.
12.
13.
14.
Booklet B (Answers)
b) Cell membrane.
a) The plastic bag is semi-permeable and only allows the iodine solution to enter but not the starch solution to exit.
a) Their seeds are dispersed by animals.
b) Animals eat the fruits in Group B and pass the seeds in the fruits, while in Group A, the seeds are left behind by the animals.
a) The amount of soil used was different for each pot.
b) The garden soil would be the best because it consists of equal amounts of sands and clayey soil and therefore does not allow too much or too little to pass through. It also contains decaying materials which will act as nutrients for the plant. a)
Glass Tube: Windpipe
Balloons: Lungs
b) The balloon would be in flattened and then deflated.
a) He is trying to find out if a decaying/decomposing prawn produces carbon dioxide.
b) Materials which are bio-degrable can be damaged and will disappear, not pollute the environment and also provide nutrients to the plants.
a) Light
b) With sunlight, the plany photosynthesizes, producing oxygen which the lizard and flies need to respire.
c) Plants produce oxygen which animals need to survive.
a) Acrobat A could jump at a greater height.
b) The amount of gravitational potential energy depends on the height and weight of an object. Since the height of acrobat B and C are the same and acrobat C is heavier than acrobat B, more gravitational potential energy can be converted into more kinetic energy.
a) The magnetic strength of a bar magnet does not depend on its size. b) T
a) 6cm
c) 13cm
b) Spring P is more elastic. Each time a 20g load is attached on spring P, the length increases by 3 cm. However, each time a 20g load is attached on spring Q, the length increases by only 2cm.
b) No, it did not because the glass contained air which prevents all water from entering.

15. Inelasticity
Materials that do not resume their original shape after being deformed are said to be inelastic.

16. Hooke’s Law British physicist Robert Hooke
Hooke’s Law – The amount of stretch or compression (change in length), Δx, is directly proportional to the applied force, F.
𝐹~∆𝑥

17. If an elastic material is stretched or compressed beyond a certain amount, it will not return to its original state and will remain distorted.
The distance beyond which permanent distortion occurs is called the elastic limit.
Hooke’s law holds only as long as the force does not stretch or compress the material beyond its elastic limits.

18. Tension & compression

19. When something is pulled on (stretched), it is said to be in tension.
When it is pushed in (squashed), it is in compression.
Compression causes things to get shorter and wider, whereas tension causes them to get longer and thinner.

21. Simple Beam
Figure 12.9
Its supported on both ends and it carries the load in the middle.

22. I-Beam One flange is squeezed while the other is stretched.
The two flanges carry all stresses in the beam.
The web acts to hold the top and the bottom flanges apart. This is a relatively stress free region.

23. Arches

24. Arches
When a load is placed on a properly arches structure, the compression strengthens rather than weakens the structure.
The stones are pushed together more firmly and are held together by compressive forces.
With the right shape, the stones don’t even require cement to hold them together.

25. Arches
When the load being supported is uniform and extends horizontally, as with a bridge, the proper shape is a parabola.
The curve that gives it maximum strength is called a catenary.
A catenary is the curve formed by a rope or chain hung between two points of support. Tension along every part of the rope or chain is parallel to the curve.

26. Domes
If you rotate an arch through a complete circle, you have a dome.
The weight of the dome, like that of an arch, produces compression.

27. Scaling

28. Scaling
The study of how the volume and shape (size) of any object affect the relationship of its weight, strength, and surface area.

29. Strength & Weight Strength is related to the area of the cross section
This is 2-dimensional
Measured in square centimeters
Weight relates to its volume.
This is 3-dimensional
Measured in cubic centimeters

30. Scaling In Nature
We find in nature that large animals have disproportionally thick legs compared with those of small animals.
This is because of the relationship between volume and area
Volume and weight grow as the cube of the factor by which the linear dimension increases, while strength and area grow as the square of the increase factor.
The compression of the total surface area to volume is also important.

31. White Board Questions…
Could King Kong really exist?
Explain using the scaling notes we just took.
What other characteristics of an animal do you think are affected by scaling?