Reducing Unwanted Energy Transfers



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  • Lubrication reduces frictional forces
  • If something is moving, there is usually a frictional force acting against it= causes some energy to dissipate
  • Objects which are being rubbed together = lubricants used to reduce the friction between them when they move.
  • Lubricants are usually liquids (oil) = flow easily between objects and coat them
  • Insulation = reduces the rate of energy transfer by heating
  • Prevent heat loss in houses:
  • Thick walls made from a low thermal conducting material = slow rate of energy transfer = cool more slowly

    Thermal insulation:

    1. Cavity walls (made up of an inner and outer wall with an air gap in between) = reduces the amount of conduction through the walls. Cavity insulation (cavity wall air gap is filled with foam) = reduce energy transfer by convection

    2. Loft insulation = reduce convection currents

    3. Double – glazed windows = have an air gap between two sheets of glass = prevent energy transfer by conduction

    4. Draught excluders = reduce energy transfers by convection

  • Practical to investigate the effectiveness of materials as thermal insulators:
  • 1. Boil water and pour some into a sealable container. Measure the mass

    2. Measure the initial(starting) temp of the water using a thermometer

    3. Seal container and leave for 5 minutes using a stopwatch

    4. Remove lid and measure the final temp

    5. Pour water away and allow the container to cool so it goes to room temperature

    6. Repeat but wrap the container in different materials once it has been sealed. It is important to use the same mass of water at the same initial temperature

    7. Lower temp difference = better the material is as a thermal insulator

    8. could also investigate how the thickness of a material affects how good a thermal insulator it is. Thicker = smaller temp change = less energy transferred= better thermal insulators

How long have you…? (present perfect 4) Exercises


 

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Use the information given to create questions beginning with ‘How long…?’

• It is snowing.

• The weather is shining.

• John and Kate are married.

• My brother has gone on holiday.

• My aunty and uncle live in Canada.

• My sister is a teacher.

• I work at the chemist.

• I’ve known Susan since I was a baby.

• Jonathan is learning to speak to Mandarin.

 

 

 

Fill in the missing gaps in the sentences using the present perfect (=has/have + past participle)

• I have known Kate a long time.

• My brother has been playing the piano he was 11 years old.

• My mum and dad on holiday to America. They

gone since last Sunday.

• I Ben and Emma since primary school.

We to the same primary and secondary school.

• My sister learning to speak French because she
is going to France next month.

 

 

Use the appropriate words in the missing gaps.

have you lived       lives      to

has been       works        have known

I have bought       have worked.

• My sister in Spain. She is studying Spanish

with her friend Rosie. I Rosie since I was 5.

• Spencer like with Jamie. They have worked

together for 2 years.

• How long in Australia?

• a new dress for prom.

• He to Thorpe park.

 

 

Challenge: Create 4 of your own questions beginning with ‘How long……?’

1.

2.

3.

4.

 

 

 

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“Every accomplishment starts 
With the decision to try.” Gail Dever

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