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“We must trust to nothing but facts: These are presented to us by Nature, and cannot deceive. We ought, in every instance, to submit our reasoning to the test of experiment, and never to search for truth but by the natural road of experiment and observation.” ― Antoine Lavoisier, Elements of Chemistry

c h e m i s t r y 4 u s

The science of today is the technology of tomorrow, Edward Teller

c h e m i s t r y 4 u s

Success is no accident. It is hard work, perseverance, learning, studying, sacrifice and most of all, love of what you are doing or learning to do. Pele

c h e m i s t r y 4 u s

Optimism is the faith that leads to achievement. Nothing can be done without hope and confidence. Helen Keller

c h e m i s t r y 4 u s

Science without religion is lame, religion without science is blind. Albert Einstein

c h e m i s t r y 4 u s

Insanity: doing the same thing over and over again and expecting different results. Albert Einstein

Monday, 27 November 2017

Formula List for IGCSE Physics

Formula list for IGCSE Physics

Tuesday, 21 November 2017

Iron Extraction-IGCSE CHEMISTRY

Iron is only a moderately reactive metal - but it is less reactive than Carbon.

Because of this is can be smelted displaced from Iron compounds by heating with Carbon (coke).

Iron compounds are found in rocks - we call rocks with high percentages of Iron compounds Iron ore.

The best known Iron ore is called Haematite (Haem - means Iron, as in Haemoglobin)

It contains Iron Oxide and many  impurities.

It is dropped into the top of a blast-furnace along with Coke (purified Coal, almost pure Carbon) and Limestone (Calcium Carbonate).


Hot air is blasted in from the side to provide Oxygen that allows some of the Carbon to burn, releasing enough heat to raise the temperature above 1500oC.

Carbon + Oxygen --> Carbon Dioxide
C (s)  + O2(g) --> CO2(g)

However, not enough Oxygen is added for complete combustion so some Carbon Monoxide is made.

Carbon Dioxide + Carbon --> Carbon Monoxide
CO2(g) + C (s)--> 2 CO(g)

Carbon Monoxide is toxic but its presence in the Blast Furnace is important to how the process works because it removes Oxygen from (Reduces) the Iron Oxide to Iron.

Carbon Monoxide + Iron Oxide --> Iron + Carbon Dioxide.

3 CO(g) Fe2O3 (s) --> 2 Fe (l) + 3 CO2(g)

The Iron is dense and liquid and so flows to the bottom of the furnace.

The Carbon Dioxide escapes at the top.

If the impurities in the Iron Ore were allowed to mix in with the Iron it would be brittle and useless.

But the Limestone breaks down (thermally decomposes) to form Lime which then reacts with the sandy impurities

Calcium Carbonate (Limestone) --> Calcium Oxide (Lime) + Carbon Dioxide
CaCO3 (s) --> CaO (s) + CO2(g)


Calcium Oxide + Silicon Oxide (sandy impurities) --> Calcium Silicate (Slag)
CaO (s) +SiO2(s) --> CaSiO3(l)

The slag also flows to the bottom of the furnace but is less dense than the Iron and so floats on top, allowing them both to be tapped off separately.

source: https://sites.google.com/site/internationalgcsechemistry/year-10-topics/extraction-and-uses-of-metals/3---extracting-iron



Sunday, 16 April 2017

Exercise - Pre Exam Science (Physics) for Checkpoint + KEY ANSWER








KALAM KUDUS CHRISTIAN SCHOOL – INTERNATIONAL PROGRAM
Preparation – Cambridge Checkpoint Examination
@phy2

CANDIDATE NAME       :
CENTER ID                   :
           
1.  The diagram shows a helicopter in the air.
The arrows show the directions of the four forces which can act on it.

(a) Two of the forces must be equal for the helicopter to stay at the same height.
      Which two forces?

................... and ................... [1]
      The next diagram shows the sizes of the four forces at a different stage in its flight.
(b) Draw an arrow on this diagram to show which direction the helicopter will move. [1]


(c) The helicopter is now on the ground and the engine is turned off.
It is on level ground and there is no wind blowing.
The next diagram shows the direction of one force, C, acting on the helicopter.

(i) Write down the name given to force C.

..............................................................................................................................[1]
(ii) One other force is acting on the helicopter when it is on the ground.
     Draw an arrow on the diagram to show the direction of this other force. [1]




 2. The boxes show some facts about the Earth’s movement and some observations.
(a) Draw a line from each fact to match its observation.
     The first one has been done for you.
[2]


(b) Tick (√) one box next to the planet that can never be seen in the sky all night.
[1]


3. This is a question about fuels.
(a) Name three fossil fuels.
1..................................................................................................................................
2..................................................................................................................................
3..............................................................................................................................[1]
(b) Write down one disadvantage of burning fossil fuels.
....................................................................................................................................
................................................................................................................................[1]
(c) Wood is a type of biomass which can be used as fuel.
     What is meant by the term biomass?
....................................................................................................................................
................................................................................................................................[1]
(d) Wood is also a renewable fuel.
      What is meant by the term renewable?
....................................................................................................................................
................................................................................................................................[1]
(e) State one disadvantage to the environment of cutting down trees to get wood for fuel?
....................................................................................................................................................................................................................................................................[1]


4. Simran has been measuring the time taken for different objects to slide down a ramp. The picture shows the ramp with one of the objects, a pencil case, on it.

(a)   On the picture, draw an arrow to show the direction of the force of friction on the pencil case. [1]
(b)    
(b) When timing the different objects, the test should be made fair.
One factor to keep constant is the distance that the object slides.
State two other factors which need to be kept the same for each test.
1..................................................................................................................................
2..............................................................................................................................[2]
Simran repeats the test with the pencil case and records the results in this table.

She thinks there may be something wrong with her second time.

(c) Why might she think this?
....................................................................................................................................
................................................................................................................................[1]
(d) How could she check if the second time was wrong?
....................................................................................................................................
...............................................................................................................................[1]


5. Complete the boxes beside each picture to record the reading on each piece of   
    equipment.
(a)   Measuring cylinder in cm3.

[1]

(b)   Voltmeter in volts.

                                           [1]



6. Complete the table to show the useful energy transfer that happens in each case.
      The first one has been done for you.

[3]


7. Liz and Rena investigate how high a ball bounces. They use a metre ruler and a tennis   ball.
Liz drops the ball from different heights.
Rena watches and records the height of the first bounce.
They measure the height from the bottom of the ball.

(a) Write down one reason why Rena will find it difficult to record the height of the bounce accurately.
....................................................................................................................................
................................................................................................................................[1]
Liz and Rena repeat each test three times and work out the average for each.
They measure in centimetres (cm).
They record their results in the table below.

They have plotted three of their results on a graph.
(b) Complete the graph by:
• plotting the last two points
• drawing a best fit straight line.

[2]

(c) One advantage of plotting a graph is that the trend can be seen more clearly than in the
     table.
     Write down one other advantage of displaying results in a graph.
....................................................................................................................................
................................................................................................................................[1]
(d) Another group in the class does the test.
They plotted their results on a similar graph.
Their points were all far from their line.
What does this suggest about their results?
...................................................................................................................................
................................................................................................................................[1]


8. Andy and James are pulling on a rope.
    The size and direction of their pulling forces are shown.

(a) The rope does not move toward Andy or James.
Explain why the rope does not move.

....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
................................................................................................................................[2]

(b) Andy keeps pulling with the same force of 100 N.
The rope now starts to move towards him.
What must have happened to the pulling force from James?

....................................................................................................................................
...............................................................................................................................[1]






9. The diagram shows four large objects, A to D, at different places on the Earth’s surface.

(a) Draw arrows from the objects to show the force of gravity on them.
     The first one has been done for you. [2]
(b) The Moon has a smaller force of gravity than the Earth.
      Use this information to complete the sentences.
      Use the words from the list below.
greater             the same          less
The mass of object A will be ..................................... when placed on the Moon.
The weight of object A will be ...................................... when placed on the Moon.[2]

10. Brigitte plays a musical instrument called a saxophone.
     Her teacher asks her to explain the sound the saxophone makes.
(a) Complete the sentences that Brigitte writes.
      Choose from the following words.
      contract                  energy                          expand       force particle vibrate
Sound is a type of .......................................................................................................... .
Sound is made when the particles in the air .............................................................[2]

(b) Brigitte plays a note on her saxophone.

The diagram shows the pattern the note makes on the oscilloscope.
Here are some oscilloscope pictures of different notes from Brigitte’s saxophone.

(i) Which note has the highest pitch?
     Circle the correct answer.

A           B         C          D          [1]

(ii) Which note is the loudest?
     Circle the correct answer.

     A     B          C          D          [1]

(iii) Brigitte plays one note quietly and then makes this note louder.
Draw the oscilloscope picture you would see.

[2]


11.  Bruce compares the speeds of some toys down a ramp.
Here is the equipment he uses.


He places each toy on the start line and then lets the toy go.
Here are his results.

(a) Bruce keeps some variables the same.
Write down two variables he keeps the same.
1.................................................................................................................................
2 ............................................................................................................................[2]

(b) (i) Which two measurements are needed to work out the average speed of the toy
truck?
1 ................................................................................................................................
2 ............................................................................................................................[2]
(ii) Work out the average speed of the toy truck.
Include the correct units in your answer.

speed = .......................................... [3]

KEY ANSWER:
download key answer