SCIE 4001
Worksheet April 2016
Science Exam Guide - April 2016
SCIE 4001 December 2015 final exam
Point Answers SCIE4001 Final exam December 2015
 

Worksheet 1

1. Describe, with diagrams, how the particles are organized in solids liquids and gases.

soilds
liquids
  • Particles in solids are closely packed in rows and columns in three dimensions.
  • The particles maintain their relative positions.
  • Particles in liquids are loosely packed.
  • The particles do not maintain their relative positions and can move about within the bulk of the liquid (bounded by the surfaces of the liquid).
gas
gas

Closed Container

  • Particles in gases are very loosely packed.
  • The particles do not maintain their relative positions and expand to fill the entire closed container.
  • The particles can move about within the container.

Open or No Container

  • Particles in gases are very loosely packed.
  • The particles do not maintain their relative positions and expand outwards constantly escaping from the container.
 

2. Describe the movement of the particles in solids liquids and gases.

  • Particles in solids can only rotate and vibrate.
  • Particles in liquids can rotate, vibrate and translate within the bulk of the liquid.
  • Particles in gases can rotate, vibrate and translate freely to anywhere.
 

3. Describe the forces between the particles in solids liquids and gases.

  • Particles in solids have very strong inter-molecular forces.
  • Particles in liquids have strong inter-molecular forces but not as strong as in solids.
  • Particles in gases have little or no inter-molecular forces.

 

 

4. Explain how rain water becomes hard.

There are in the main four chemical substances responsible for hardness in water. They are:

  • Calcium hydrogen carbonate
  • Magnesium hydrogen carbonate
  • Calcium sulphate
  • Magnesium sulphate

These chemicals get into the water when water flows over rocks.

Temporary Hard Water

  • When rain falls it reacts with carbon dioxide to form carbonic acid.
  • If this acidic water flows over rocks containing calcium carbonate (limestone) or magnesium carbonate (dolomite) it reacts to produce calcium hydrogen carbonate or magnesium hydrogen carbonate which dissolves in the water.
  • Calcium hydrogen carbonate or magnesium hydrogen carbonate in the water react with soap and inhibits lathering.
  • This kind of hardness is called temporary hardness as it is easily removed by boiling.

Permanent Hard Water

  • If water flows over rocks containing calcium sulphate (chalk, gypsum, alabaster) or magnesium sulphate (epsom salts) it dissolves in the water.
  • Calcium sulphate or magnesium sulphate in the water react with soap and inhibits lathering.
  • This kind of hardness is called permanent hardness as it is NOT removed by boiling.
 

5. Write a word equation for the formation of hard water.

Any one of the following:

  • calcium hydrogen carbonate + sodium stearate (soap) = calcium stearate (scum) + sodium hydrogen carbonate
  • calcium sulphate + sodium stearate (soap) = calcium stearate (scum) + sodium sulphate
  • magnesium hydrogen carbonate + sodium stearate (soap) = magnesium stearate (scum) + sodium hydrogen carbonate
  • magnesium sulphate + sodium stearate (soap) = magnesium stearate (scum) + sodium sulphate
 

6. Describe how water is made safe for drinking

Water treated by Utility (WASA)

  • Removal of undissolved (suspended) solids by
    • And initial settling in the dam or ponds where most suspended matter settles out of the water.
    • If there is excess suspended material (referred to as turbidity by WASA) alum may be added to precipitate these materials.
    • Filtration by layers of gravel to remove suspended material and sometimes carbon to remove dissolved pollutants.
    • Addition of chlorine to kill harmful microbes.
  • In many cases no attempt is made to remove dissolved materials from the water. These may include:
    • Dissolved minerals in the water picked up in the ground water or surface run off.
    • Pollutants (liquid and dissolved solids including heavy metals picked up for industrial estates in the catchments area)

Treatment of Water in the Home

  • If the water in the home has not been treated with chlorine or it has become contaminated after its initial treatment the following can be done:
    • Boil water before using as this kills harmful microbes but gives the water a bland taste which can be restored by allowing the water to stand and dissolve air.
    • Treat with very small quantities of chlorine bleach – this is essentially repeating the process done at the treatment plant. The harmful microbes will be killed. The level of chlorine used should not be detectable in the taste – excess chlorine is poisonous
    • Distillation - This process will remove all dissolved materials and kill harmful microbes but is very costly except if solar stills are used.
    • Filtration - Many regular filters will only remove suspended materials leaving harmful microbes and dissolved materials in the water. As such it can give a false sense of security about the water quality consumed. Some specialized filters will remove specific dissolved materials but will leave harmful microbes in the water. Filtration therefore, should not be used as a substitute for chlorination
 

7. Explain the science behind the process of obtaining the sugar from the sugar cane juice.

  • Sugarcane is crushed and the juice collected.
  • The juice is filtered to remove undissolved solids.
  • As the juice is heated, the water evaporates and it becomes saturated.
  • Sugar crystals begin to form as the water in the saturated solution evaporates.
  • The saturated liquid remaining is called molasses.
 

8. Explain why fine sugar crystals dissolves faster than lumpy or large crystals of sugar in water.

  • Water acts only on the surface of the solute (sugar) to break the bonds between the molecules in the crystals.
  • When the bonds are broken the particles will enter the spaces between the liquid molecules.
  • A fine powder has more surface area than lumpy or large crystals of sugar.
  • Therefore, the more bonds of the fine powder will be broken.
  • Molecules of the fine powder will then enter the spaces between the liquid molecules faster.
 

9. Cane is bundled using heavy iron chains which can severely damage the jaws of the crusher. Explain why the cane is passed over a very strong electromagnet before being passed through the crusher.

  • Iron is a magnetic substance
  • Iron will be attracted to a magnet.
  • The iron chain will be pulled to the electromagnet and prevented from entering the crusher.
 

10. How can the salt be recovered from a salt and sand mixture?

  • First put the mixture in water and stir vigorously.
  • The water will dissolve the salt but the sand will be undissolved.
  • Filter the water.
  • The salt is dissolved in the water in the filtrate. Sand is the residue.
  • The salt can be recovered by evaporating the water to dryness over a flame.
 

11. Describe how you would find the density of an irregular shaped solid.

answersApparatus: Measuring cylinder, thread or thin string.
(i) Add water to the measuring cylinder so that the irregular shaped solid can be completely submerged in the water.
(ii) Read the water level in measuring cylinder.
(iii) Use a thin string to gently lower the irregular shaped solid so that it is completely immersed in the water.
(iv) Take the new reading of the water level from the measuring cylinder.
(Note to Students: The volume of water does not increase – the reading increases because the the irregular shaped solid displaces its own volume of water)
(v) The volume of the irregular shaped solid is the difference between the two readings.
(vi) Use a balance to find the mass of the irregular shaped solid.

(vii)    
mass
  density =
——————
     
volume

Calculate the density from the formula above.

 

12. Explain the term Work.

  • Work is done when a force moves an object in the direction of the force.
  • When work is done energy is expended.
 

13. Draw a labeled diagram of a circuit with two cells (C1 and C2), and switches (S1, S2 and S3) to independently control three bulbs.

circuit

 

14. Add a fourth switch (S4) in the above circuit that will switch off all three bulbs.

circuit

 

15. Describe the function the circuit breaker in the house or the fuse in a car.

These prevent overload of circuits and the danger of fire or electrical shock by stopping the current from flowing in the circuit if it is overloaded.

 

16. How does the fuse work?

It burns out if the circuit is overloaded and stop current from flowing in the circuit.   

 

17.Define the term conductor and give an example.  

A material which allows energy (electricity , heat or sound) to flow through easily. Metal (e.g. aluminum, iron, steel, copper, brass, bronze) 

 

18. Define the term insulator and give an example.

A material which does not allows energy (electricity , heat or sound) to flow through easily. Non-metal e.g. (plastic, rubber, glass, fiberglass, porcelain, ceramic, dry wood) 

 

19. You are given three identical rods and told two are magnets. Explain how you would determine which of these are magnets, without the use of additional equipment.

  • Magnets have two poles: like poles repel and unlike poles attract
  • Magnets attract ferro-magnetic materials (usually iron, nickel or chromium based)
  • The only true test for an object being a magnet is if it repels another magnet.
  • Label the rods X, Y and Z.
  • Bring the ends of the rods together in pairs (X-Y. X-Z and Y-Z).
  • Switch the ends of the pairs.
  • The two that repel each other are magnets (with similar poles near each other)
  • Test by switching the ends around (for the other pair of poles to repel each other)
  20. The sun shines on plants which are used to make bio fuels to run a turbine engine which has a generator attaches to power lights, stereo and play a CD Player. Copy and complete the following diagram to indicate the MAIN form of energy which is output from each stage.
 
                           
    Lights
     
    The sun
    plants
    biofuel
    turbine engine
    generator
    ______________
    energy
    source of
    source of
    source of
    source of
    source of
    ______________
    ______________
    ______________
    ______________
    ______________
    Stereo
    ______________
    energy
    Blender
    ______________
    energy
   
                       
Lights
 
The sun
plants
biofuel
turbine engine
generator
EMR
energy
source of
source of
source of
source of
source of
EMR
Chemical
Chemical
Mechanical Kinetic
Electricity
Stereo
Sound
energy
Blender
Mechanical Kinetic
energy
 

21. Draw a labeled diagram of a thermometer.

thermometer  
   
 

22. Define conduction, convection and radiation giving examples.

light
  • Process of conduction involves heat traveling from particle to particle.
  • Best seen in solids.
  • From high temperature to low temperature.
answers
  • Convection is the transfer of heat through a process where the fluid (liquid or gas) itself moves.
  • When the bottom of the fluid is heated it expands and thus gets less dense than the colder fluid.
  • The hot (less dense) fluid rises and cold fluid rushes in to take its place.
  • The continuous cycle of movement is called a convection current.
 

23. Two children playing near a swimming drop a toy into the water which sinks to the bottom of the pool. Using a ray diagram trace two rays of light from the toy to the eye of a person on the bank. Explain the principle which causes light to behave in this manner.

light

Diagram:
• Two rays from the bottom
• Two rays bent at the surface
• Two rays projected backward

Explanation
• Refraction occurs when light moves from one medium to another and changes direction
• Light travels in straight lines
• The eye projects the rays from the direction in which they enter the eye

   
 

24. What are the primary colors of light?

light
Three colors that can be mixed to produce any other colored light
Red + blue + green = white light
   
 

25. Discuss the speed of sound in solids, liquids and gases.

  • Fastest to slowest speed: Land, water, air
  • Sound moves from particle to particle.
  • Particles in solids are closest and do not move around so they conduct the sound best.
  • Particles in liquids move around and are further apart so they are not as good conductors of sound as solids.
  • Particles in gas move around and are furthest apart so they are not as good conductors of sound as solids and liquids.
 

26. Discuss the similarities and differences between science and technology.

Similar
Human Activities
Use research
Use cyclic activity
Have processes
Study the world around us to create new knowledge
     
Different    
  Science Technology
Nature Science is knowing about the natural world Technology is doing activities which modify, change or control the natural world
Goals The search for and theorizing about cause driven by curiosity The search for and theorizing about new processes driven by needs and wants
Value Making virtually value-free statements Activities always value-laden
Evaluation Methods Observation, hypothesis, testing hypothesis and creation of theories Analysis and synthesis of design
Goals achieved through Corresponding Scientific Processes Key Technological Processes
Focus Focuses on understanding natural phenomena Focuses on understanding and improving the man-made environment
Development Methods Discovery (controlled by experimentation) and sometimes serendipity Design, invention, production
Strength Drawing correct conclusions based on good theories and accurate data Taking good decisions based on incomplete data and approximate models
Skills needed to excel Experimental and logical skills Design, construction, testing, planning, quality assurance, problem solving, decision making, interpersonal and communication skills
     
 

27. Explain the technological processes.

 
answers
 

28. Explain the relationship between function and form in two named everyday structures.

  • Associated with modernist architecture and industrial design in the 20th century is a principle that form follows function. 
  • The principle is that the shape of a building or object should be primarily based upon its intended function or purpose.
  • The floors and walls of a bathroom should be made of waterproof materials and designed so that waste water runs out easily as its function is for bathing.
  • A dining table should have a flat top and sturdy legs so that eating utensils will not slide off easily and there will be no wobble or shake to create spills from food and drink.
  29. Give a brief explanation with an example of how ANY FOUR (4) simple machines work.
lever

Levers
A lever is one of the simplest mechanical devices. A lever can be made from a beam or stick or rod with a sharp edge on which to pivot. This pivot is called a fulcrum. A lever is often used to magnify the effort exerted to lift weights with less effort, but levers can sometimes be used where the load is smaller than the effort. When you use a crowbar, for example, to open box or a nail to open a paint can or a board to move a crate you demonstrate the principle of levers.

wheel and axle

Wheel & Axle
A circular device to which is attached a rigid axle at its centre can be used as a force or distance multiplier.
— When a rope is attached to the axle, the force is applied to the wheel and as the wheel is rotated the rope winds around the axle with a force much greater than that used to rotate the wheel.
— When the axle is rotated the wheel moves a much greater distance than the axle.

wedge
Inclined Plane
The inclined plane is any flat, sloping surface raised at an angle.
— It is a way of lifting a load that would be too heavy to lift straight up by using a ramp.
— The steeper the ramp, the more effort is required.
— Staircases are a special case of inclined planes.
— When building roads or pathways the steepness has to be considered.
— Although the distance covered in a slight slope is longer than that of a steep slope, the effort required for the steep slope is much more.
wheel and axle

Pulley
A pulley is a wheel with a groove along its edge, where a rope or cable can be placed.
— It applies the principle of applying force over a longer distance
— It changes the direction of the applied force.
— Complex pulley systems of can be used to generate large forces, especially for lifting objects.

 

screw

Screw
A screw is a shaft that has a in inclined groove along its surface.

— When the screw is rotated, the force is applied perpendicular to the groove.
— A small rotational force is translated into a large linear one.
— Screws are frequently used to fasten objects together.
— The screw can elevate water from a low-lying body to a higher one (known as Archimedes' screw).
— The force is perpendicular to the inclined surfaces, so it pushes two objects (or portions of a single object) apart or pulls them together depending on the way it is turned.

wedge

Wedge
A wedge is a double-inclined plane (both sides are inclined) that moves to exert a force along the lengths of the sides.

— The force is perpendicular to the inclined surfaces, so it pushes two objects (or portions of a single object) apart. 
— Axes, knives, and chisels are all wedges. . 
— The common "door stop wedge" generates large frictional forces on the wedge surfaces to provide friction for keeping doors open.

30. Draw diagrams to show the THREE classes of levers work.

levers
 

A first class lever can be a force multiplier like a crowbar use to move a heavy stone
– a small force through a longer distance is use to develop a large force moving through a shorter distance (diagram above).
The first class lever to the right is a distance multiplier and can make work easier by lifting a light load through a large distance when the effort moves through a smaller distance.

 
lever
lever
A second class lever is always a force multiplier, as for example, generating a large force to remove a nail with a claw hammer or lifting a large load with a wheel barrow. A third class lever is always a distance multiplier, as for example, using a tweezers to hold a small object. Effort is the force applied; Load is the force that is required to do the Page 18 of 18 job and the fulcrum is the part of the lever which does not move.

31. State four possible effects of a force.

Any four of the following:

  • Deform an object
  • start a stationary object moving
  • Stop a moving object
  • Speed up a moving object
  • Slow down a moving object
  • Change the direction of motion of a moving object
     
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Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.