The Collection of

Physics Modifications and Characteristics

Chapter 4

(Heat)

Form 4

By: Ngu Leon Weiy

Note: No part of this whole document shall be reproduced in any means or ways.

As a researcher in a boat manufacturing company, you are assigned to study

metal characteristics used to make the boat as in diagram above.

Explain the suitable characteristics of the metal to be used as the material to

make the boat.

Determine the most suitable metal to be used as the material to make the boat

and give your reasons.

Characteristics

Explanation

- The shape of the boat must be streamlined.

- To reduce water resistance.

- The density of the metal must be low. - So it is light.

- The specific heat capacity of the metal must be high.

- So it will not heat up easily.

- The strength of metal must be high. - So it will not break or damage easily.

- S metal is chosen because the shape of boat to be built is in streamlined shape, has low density, high specific heat capacity and high strength of metal.

Modification

Explanation

- Increase the surface of fin blades. - Cools the engine faster.

- Increase the number of fin blades. - Cools the engine faster.

- Use liquid with high specific heat capacity.

- To remove more heat from the engine.

- The liquid must have high boiling point.

- So it won’t boil easily.

- The size of fan must be big. - To suck more air.

Characteristics

Explanation

- The gas container should be good conductor of heat.

- So it can conduct and absorb heat faster.

- The specific heat capacity must be low.

- So the temperature of container attains the temperature of surrounding water quickly.

- The expansion when heated must be low.

- So the volume of container can be kept constant.

- The wall of container must be thin. - So the heat can transfer quickly.

- Container R is chosen because it is a good conductor of heat, has low specific heat capacity, low expansion when heated and thin wall of container.

Diagram below shows a lamp but it is no suitable for the use of student as desk

lamp for study.

Modification

Explanation

- Use fluorescent lamp. - It has higher efficiency and consumes less power.

- The lamp is covered with white colour.

- To reduce the heat absorbed.

- Adjustable stand is used. - So the height of lamp can be adjusted.

- The lamp is connected with earth wire.

- To prevent short circuit.

- The lamp used should be energy saver lamp.

- It produces the same brightness with less consumption of power.

Characteristics

Explanation

- The kettle should have low mass. - So it is easy to carry and can reduce loss of heat to surrounding.

- The specific heat capacity of kettle must be low.

- So it can minimise the loss of heat to surrounding.

- The outer surface should be shiny. - To reduce loss of heat and increase efficiency.

- The power must be high. - So it can boil the water faster.

- M kettle is chosen because it has low mass, low specific heat capacity, shiny outer surface and high power.

Anandon bought a new resort home in Kundasang. He finds that the house is

not comfortable because of the coolness; especially at night. He decides to

install a heating system to overcome the problem. The heating system used by

him needs to heat up the floor before heat up the air in the house. Discuss the

design of the heating system from the aspect of the:

- Heating agent used.

- Material and structure of the piping system to transfer heat through the

floor.

Modification

Explanation

- Liquid is used as the cooling agent. - So it can absorb heat and transfer it to another area.

- The liquid agent should have high specific heat capacity.

- To absorb more heat.

- The boiling point of the cooling agent must be high.

- So it will not boil easily.

- Material for the pipe must be good heat conductor.

- So the rate of heat transferred to the floor is faster.

- The pipe is in coiled structure. - To increase heat transfer.

Modification

Explanation

- High specific heat capacity of liquid. -To absorb large amount of heat and transfer it.

- The liquid has high boiling point. - So it will not boil easily.

- The pipe has low rate of rusting. - It will not rust easily.

- The material used for the transmission pipe must be strong.

- Will not break easily.

- The size of fan must be big. - To blow large amount of heat.

Characteristics

Explanation

- The specific heat capacity of the ice cream box must be low.

- To cool up faster.

- The size of ice cream box must be small.

- Easier to carry.

- The material for the outer box must be plastic PVC.

- It is a poor conductor of heat.

- The outer box should be painted with bright colour.

- Bright colour does not absorb heat.

- R is chosen because it has low specific heat capacity ice cream box, small size of ice cream box, outer box made of plastic PVC and painted with bright colour.

Modification

Explanation

- The number of compression blades is increased.

- To increase the air intake.

- The blade should be made of strong material.

- Will not break easily.

- Fuel injectors are increased. - For burning more fuel and producing more force.

- The size of combustion chamber is increased.

- More fuel to be burnt.

- Decrease the size of nozzle. - To eject gas a high speed.

Characteristics

Explanation

- Fins must with low specific heat capacity.

- Faster to get hot.

- Melting pint must high. - To withstand high temperature.

- It must be good conductor of heat. - The heat can be lost easily.

- Rate of expansion should be moderate.

- The shape of fins will not deform easily.

- P is the most suitable because it has low specific heat capacity of fins, high melting point, is a good conductor of heat and moderate rate of expansion.

A group of 7 scientists from Malaysia will be making an expedition to the

Antartic to conduct some experiments. After a survey, it is found that transport

will be needed to ferry the 7 scientists around. It is suggested that a Malaysian-

made 7-seater MPV be used as it can accommodate 7 people at a time but

modifications need to be carried out on the car to suit the climate and terrain of

the land there. Suggest and explain what modifications need to be carried out to

the car.

Modification

Explanation

- Wide tyre must be used. - To reduce pressure acting on the snow.

- Tyre with teeth-like treads or similar features should be used.

- To give a better grip on a hilly terrain.

- A heater should be installed. - To maintain the temperature at a bearable level.

- The body should be made of good insulating materials.

- To reduce heat loss.

- Use lighter but strong materials to build a car body.

- To reduce pressure on the snow.

It is found that the chicken is not evenly cooked in the oven.

Modification

Explanation

- The shape and length of the heating element must be coiled and long.

- To increase the surface area to supply heat.

- The bottom of the oven should be equipped with one more heating element.

- So the bottom of the food can be cooked also.

- The inner wall of the oven should be made of good insulating material.

- To trap heat and reduce heat loss to the surrounding.

- Glass door should have double layers and air between the layers.

- To reduce heat loss to the surrounding.

- Electric motor is used to rotate the food.

- So the food can cook evenly.

Modification

Explanation

- More ice should be added. - More heat can be absorbed from the drinks.

- Use white painted container. - White colour is poor absorbed of heat.

- The container should be made of heat insulator such as plastic.

- To reduce the absorption of heat.

-The container should be made of material with high specific heat capacity.

- So the container will not be easily heated up.

- Cover the container. - To reduce heat absorbed from the surroundings.

Table shows four plastic boxes with different specifications.

You are required to determine the most suitable box for storing freshly caught

fish. Ice cubes are added to the fish in the box. Study the specifications of all the

four storage boxes from the following aspects:

Density of the plastic material

Specific hear capacity

Conductivity of the material

Structure of the sides

Explain the suitability of the aspects. Justify your choice.

Characteristics

Explanation

- The density of the plastic material must be low.

- So it is light.

- The specific heat capacity of the plastic should be high.

- So it will not heat up easily.

- The plastic material should have poor conductivity of heat.

- So it will not conduct a lot of heat into the box.

- The sides should have air layers. - To reduce the heat transfer of heat through conduction.

- Plastic box R is chosen because it has low density, high specific heat capacity, poor conductivity of heat and air layers.

Characteristics

Explanation

- The specific heat capacity must be low.

- So the plate can absorb heat faster.

- The plate should have high rust-proof.

- So it will not rust easily.

- The density of the material must be low.

- So it is lighter.

- The strength of material must be high. - So it will not break easily.

- Plate R is chosen because it has low specific heat capacity, high rustproof, low density and high strength.

Modification

Explanation

- Material of base of the pressure cooker must be low heat capacity.

- Pressure cooker can be heated faster.

- Material of handle of the pressure cooker must be high heat capacity.

- Handle will not be heated faster.

- Wall of cooker must be thick. - So it can withstand high pressure.

- It must be equipped with release valve.

- Excess steam can be released and high pressure can be released.

- Rubber should be put below the lid. - Produce air tight space in the cooker.

Characteristics

Explanation

- The coolant should have high specific latent heat of vaporisation.

- To remove heat faster.

- The coolant should have high boiling point.

- It will not boil easily.

- The specific heat capacity of pipe must be low.

- So it can heat up faster.

- The diameter of pipe should be big. - To carry more coolant.

- Coolant Q is chosen because it has high specific latent heat of vaporisation and high boiling point.

- Pipe Z is chosen because it has low specific heat capacity and big diameter.

Diagram show the cross section of a household refrigerator.

Explain how you would modify the refrigerator in diagram above into a high-

quality commercial refrigerator for food service and restaurant. In your design,

emphasise the following aspects:

(i) The size, structure and material of the refrigerator cabinet.

(ii) Ways to improve the efficiency of compression process and release of the

coolant.

(iii) Practices or features for efficient use of the electrical energy.

Modification

Explanation

- The cabinet is made of stainless steel. - To resist heat and humidity of commercial kitchens.

- The cabinet is enlarged. - To store more food.

- A more powerful compressor is installed.

- To provide cool air quickly when temperature in the refrigerator rises.

- Separate the freezer and the chiller into a few sections with separated doors.

- To save the electrical energy by reducing the heat flow into the cabinet when the doors are opened.

- Under-counter drawer is used to replace side door.

- The drawer can prevent the cool air from flowing out when food is taken from refrigerator frequently.

Diagram below shows a refrigerator.

Explain the suitability of each characteristic of the refrigerators and determine

the most suitable refrigerator which is constantly cold, energy saving and lasting

for the purpose of keeping the freshness of the food stored in it.

Give reasons for your choice.

Characteristics

Explanation

- The material used to make the decks must be tempered glass.

- So it is able to withstand weight and does not break easily.

- The lighting illumination in the refrigerator must be light-emitting diode.

- No heat emission and more energy saving.

- The power consumption must be low. - So it consumes less power and produces more energy.

- The chilled air is blown out from every deck.

- To ensure sufficient chilled air circulation throughout the fridge.

- Refrigerator B is chosen because it has decks made of tempered glass, light-emitting diode as the lighting illumination in the fridge, low power consumption and chilled air blowing out from every deck.

Modification

Explanation

- Pipe in coiled shape is wrapped around the freezer.

- Increase the area will increase the rate of heat absorption.

- Pipe is made of material with low specific heat capacity.

- So it is a good conductor of heat.

- Freon is used as the cooling liquid. - It can easily evaporate at low temperature and pressure.

- The box is wrapped with insulator. - To reduce the flow of heat from surrounding to the box.

- It is equipped with thermostate. - To control the temperature.

Modification

Explanation

- The body is made of material with low density.

- So it is lighter.

- The rice bowl is made of material with low specific heat capacity.

- So the rice cooker can cook food faster.

- The heating element should be long and is placed at the centre of cooker.

- Most of the heat can be generated to cook the rice.

- The outer layer is made of material with low conductivity of heat.

- The body will not loss too much heat to the surrounding.

- The rice bowl is closed tightly. - To prevent loss of heat to the surrounding.

Modification

Explanation

- A concave mirror is used. - So the light can converge to the focal point.

- The water container must be put at the focal point of the mirror.

- To focus maximum light onto the container.

- The outer surface is painted with black colour.

- To absorb heat.

- The material used must be metal. - Metal is good conductor of heat.

- The inner part of the container is wrapped with aluminium foil.

- So sunlight can reflect back to the cooker.

You are required to determine the most suitable solar cooker for efficient

cooking. Study the specifications of all the four solar cookers based on the

following features:

- Type of window

- Number of reflectors

- Type of lid

- Arrangement of the aluminium pot

Explain the suitability of each feature. Justify your choice.

Characteristics

Explanation

- The window must be glass. - To withstand high temperature and will not melt easily.

- Use double reflectors. - To reflect more light.

- The type of lid must be clear glass lid. - To observe the cooking food.

- Use dark aluminium pot suspended in a clear pot.

- To trap heat inside.

- S solar cooker is chosen because it has glass window, double reflectors, clear glass lid and uses dark aluminium pot suspended in a clear pot.

Explain the properties of a solar heater which can quickly heat water. Determine

the most suitable solar heater to quickly heat water and give your reason.

Characteristics

Explanation

- Concave mirror is used. - For reflecting and converging solar energy to solar heater

- Concave mirror with small aperture is used.

- So it has a small focal length.

- The surface should be blackened. - To increase the absorption of solar heat.

- The specific heat capacity must be low.

- So it heats up easily.

- Solar heater R is chosen because it uses concave mirror, concave mirror with small aperture, blackened surface and low specific heat capacity.

Modification

Explanation

-The wall of the container must be made of metal.

- Metal is a good conductor of heat.

- Concave mirror should be used as the mirrors.

- So the light rays from the sun can converge to the tank and the water will be heat up faster.

- Radius of curvature of the mirror must be small.

- So more light can be will be reflected to the tank.

- Colour of the tank wall should be black.

- Black colour is a good heat absorber.

- Specific heat capacity of the wall must be small.

- The tank can be heated up faster.

Modification

Explanation

- The pipe embedded in the solar panel must be long.

- To increase surface area for heat absorption.

- The pipe should be made of metal. - Metal is a good conductor of heat.

- The absorber panel should be painted with black.

- So it can absorb heat faster.

- A heat insulator is put behind the solar panel.

- To prevent the loss of heat.

- The storage tank must be put at higher place.

- To give a high pressure while supplying the water.

A manufacturer wants to produce a new product as one of the kitchen utensil.

The shape of handle has either short, thick or slim. Five models of the spatula

are given.

Table below shows the shape and the characteristics of the spatula.

Explain the suitability of each characteristic of the materials in table above.

Determine the most suitable spatula for marketing purpose.

Characteristics

Explanation

- The specific heat capacity of the spatula must be high.

- So it will not heat up easily.

- The melting point of spatula must be high.

- So it will not melt easily.

- The density of the spatula must be low.

- So it is lighter.

- The shape of the handle must be slim. - So it is easily to use and hold to stir the food.

- Spatula R is the most suitable because it has high specific heat capacity, high melting point, low density and slim handle.

Explain how you would design a thermometer which has high sensitivity and

responds quickly to change in temperature. In your explanation, you should

emphasise the following aspects:

(i) glass-walled bulb

(ii) diameter of capillary tube

(iii) glass-bore stem

(iv) shape of the glass-bore stem

(v) equipment to enhance the convenience of using the thermometer

Modification

Explanation

- The wall of the bulb must be thin. - To respond to the heat faster.

- The diameter of the capillary tube must be small.

- To increase the sensitivity of thermometer.

- The glass-bore stem should be narrow. - To increase the sensitivity.

- The wall of the glass-bore should be thick and curved.

- For easier reading and reducing the loss of heat.

- A constriction should be equipped to it.

- So the reading of thermometer can still be taken after some time.

Characteristics

Explanation

- The freezing point must be low. - So it won’t freeze easily.

- The boiling point of liquid must be high.

- So it won’t boil easily.

- The liquid used must be opaque. - It is easier to take reading.

- The thickness of glass walled bulb must be thin.

- To increase its sensitivity.

- Thermometer R is chosen because it has liquid with low freezing point, high boiling point, is opaque and thin glass walled bulb

A research project is carried out on the weather of a region with the surrounding

temperature is between -40°C to -8°C. Thermometer is an equipment to be

taken for the research project.

As a researcher, you are required to determine the most suitable thermometer to

be taken with as one item of the equipment. Study the characteristics of all the

five thermometers based on the following aspects:

- The liquid used

- Glass wall bulb

- Diameter of capillary tube

- Glass bore stem and cross section

Explain the suitability of the aspects.

Justify your choice.

Characteristics

Explanation

- Alcohol is used. - To record low temperature.

- Thin glass walled bulb is used. - More sensitive

- Small diameter of capillary tube is used.

- To increase the sensitivity.

- Thick and curved glass bore stem is used.

- Easier to take reading.

- T is chosen because it uses alcohol as the liquid, thin glass walled bulb, small diameter capillary tubes and thick and curved glass bore stem.

Characteristics

Explanation

- Hollow stopper is used. - To prevent heat loss through conduction.

- Double layer wall made of glass. - Higher specific heat capacity.

- Vacuum in between the double layer. - To prevent heat loss.

- Low density. - Lighter.

- S is the most suitable thermos because it has hollow stopper, glass double layer wall, vacuum between the double layer and low density.

Based on the information given in table above, explain the suitability of the

lenses for use by a watch repairer in repairing watches. Determine the most

suitable lens for the watch repairer to observe the finer parts of a watch.

Characteristics

Explanation

- The type of lens must be convex lens. - So the light can be converge to the focal point.

- Clear glass is used. - To produce clearer and brighter image.

- The power must be high. - To produce high magnification.

- The diameter must be small. - So it can be arranged to produce a virtual, upright and enlarged image.

- Lens C is the most suitable because it is a convex lens, clear glass, high power and small diameter.

Modification

Explanation

- Specific heat capacity of the wok must be low.

- So it can heat up faster.

- Thermal conductivity of the wok must be high.

- So it will be able to conduct heat faster.

- Melting point of the wok must be high.

- So the wok can withstand high temperature and will not melt easily.

- Specific heat capacity of the cooking oil must be low.

- So it can heat up faster.

- The boiling point of the cooking oil must be high.

- So it will not boil easily.