Physics

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What are the properties of solids?

Arranged in neat rows, fixed in place but vibrating, keeps in shape in a container and cannot be compressed

What are the properties of liquids?

Still touching but can move around, can be poured, takes the shape of a container and cannot be compressed

What are the properties of gases?

Fast moving, spread out meaning it can be compressed, fills the entire container

Define Density

How much mass is in a given volume Signup and view all the answers

What is the density equation?

Density = mass/volume Signup and view all the answers

Practical - Density (regular)

→ Measure the height / width / length of the object and multiply them together ( if a cuboid ) to get the volume . For a prism / cylinder you would work out the cross sectional area then multiply it by the length . → Measure the mass of the object by using a mass balance → Divide the mass by the volume Signup and view all the answers

Practical - Density (irregular)

→ Measure the mass of the object by using a mass balance → Measure the volume of the object by using a displacement can and a measuring cylinder → The volume of the water which is displaced out of the displacement can into the measuring cylinder when the object is added is the volume of the object → Divide the mass by the volume Signup and view all the answers

What are the three main types of energy transfer?

Conduction, convection and thermal radiation Signup and view all the answers

How does heat travel?

From a hot place to a cold place Signup and view all the answers

What will a hot drink do in a room?

cool down Signup and view all the answers

What will a cold drink do in a room?

Warm up Signup and view all the answers

What type of wave is infrared radiation?

Electromagnetic Signup and view all the answers

Electromagnetic waves can travel through a vacuum as no particles are involved

True Signup and view all the answers

The hotter the object...

the more thermal radiation it emits Signup and view all the answers

What do we use to see infrared radiation?

thermal image camera Signup and view all the answers

The type of surface affects...

how much thermal radiation it absorbs or emits Signup and view all the answers

Types of surfaces and what they are used for

Good absorber and emitter = Black and Matt Bad absorber(good reflector) poor emitter = White and silver/smooth Why are houses in Spain white? = Reflect the thermal radiation, keeping them cool Why are solar panels black? = Absors thermal radiation so water heats up quicker Signup and view all the answers

Investigate how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface .

<ol> <li>Pour 200cm³ of hot water into the silver can and the same volume in the black can</li> <li>Record the starting temperature of water in each can</li> <li>Record the temperature of each can every minute for 10 minutes</li> <li>At the end , calculate the temperature drop for the water in each can .</li> <li>Compare your results to your hypothesis and write a conclusion</li> </ol> Signup and view all the answers

Conduction doesn't need particles so it can travel through a vacuum

False Signup and view all the answers

Where does conduction work best?

In solids as the particles are close together Signup and view all the answers

Where does conduction work worst?

In gases as the particles are far apart Signup and view all the answers

How do particles pass energy in a solid?

Particles gain energy so they vibrate more. This makes them collide with their neighbouring particles. The collisions pass the energy from one particle to the next. Signup and view all the answers

What makes metals fantastic conductors?

they contain free electrons. The free electrons can diffuse quickly along the metal taking heat energy with them. Signup and view all the answers

What are bad conductors called?

Insulators e.g. plastic and wood Signup and view all the answers

How to reduce conduction?

Use either a vacuum (no particles no conduction) or some trapped air as it is a bad conductor e.g. vacuum flask, double glazing and duvet/clothes. Signup and view all the answers

How to reduce radiation?

Silver surfaces reflect the radiation back onto the hot object e.g. Space blankets, wrapping hot food in tin foil Signup and view all the answers

Factors affecting heat loss

-Surface area - bigger more heat loss <ul> <li>Material the object is made from (conductor or not)</li> <li>Surface the object is on (again conductor or not)</li> </ul> Signup and view all the answers

Which factor does NOT affect heat loss?

The shape of the object Signup and view all the answers

How do animals' ears affect heat loss?

big ears, large surface area, lots of heat transfer so good in the desert and small ears, small surface area, small heat transfer so good in cold places Signup and view all the answers

The bigger the temperature difference...

the bigger the heat transfer Signup and view all the answers

How does the roof nsulated the house?

Fibre glass insulation (reduces conduction and convection) Signup and view all the answers

Hwo do windows insulate the house?

Double-glazing (reduces conduction because of the air gaps inbetween the glass) Signup and view all the answers

What affects how much heat is lost through walls?

The thickness and thermal conductivity of the walls Signup and view all the answers

How do the walls insulate the house?

Cavity fibre glass (gap between walls filled with insulating fibre glass contains trapped air which cannot move so no convection) Signup and view all the answers

How does the floor insulate the house?

Carpet and underlay (poor conductor) Signup and view all the answers

How does the door insulate the house?

UPVC (poor conductor) Signup and view all the answers

How does the humble draught excluder insulate you house?

Prevents draughts caused by convection Signup and view all the answers

Define payback time

how long you have to wait to save back money on your energy bills compared to how much it cost to buy. Signup and view all the answers

payback time equation

payback time = cost of insulation/energy bill savings Signup and view all the answers

The sooner the insulation pays for itself...

the more cost effctive it is Signup and view all the answers

Chemical energy

Released during chemical reactions (like when a fuel is burnt) Signup and view all the answers

Kinetic energy

All moving objects have kinetic energy (more speed more kinetic energy) Signup and view all the answers

Gravitational potential energy

Stored energy that objects get as they are moved upwards against the force of gravity Signup and view all the answers

Elastic potential energy

Stored energy when an elastic material is stretched or squashed (springs back to original shape) Signup and view all the answers

Internal energy

the total kinetic and potential energy all of the particles have in a system Signup and view all the answers

Thermal energy

the amount of internal energy due to temperature Signup and view all the answers

Nuclear energy

Energy stored in the nucleus Signup and view all the answers

What does it mean when energy is conserved?

Energy at the start = Energy at the end Signup and view all the answers

Energy cannot be created or destroyed

True Signup and view all the answers

What pathways do we use to convert energy?

Mechanical (moving the object), electricity (using a current to transfer the energy, radiation (light sound etc) and heating by conduction Signup and view all the answers

How do we reduce friction?

using a lubricant Signup and view all the answers

Wasted energy

energy that you do not want the device to do Signup and view all the answers

Useful energy

the energy you do want from the device Signup and view all the answers

What does wasted energy do?

spreads out into the surroundings around the device (dissipates). Signup and view all the answers

Efficiency equation

Efficiency = useful energy output/ total energy input Signup and view all the answers

Power, energy and time equation

Power (W) = Energy (J)/Time (S) Signup and view all the answers

What does power tell you?

the amount of energy transferred in a second Signup and view all the answers

Study Notes

Properties of Matter

Solids have a fixed shape and volume, and their particles are closely packed.
Liquids have a fixed volume, but their shape changes, and their particles are close together but can move past each other.
Gases have neither a fixed shape nor volume, and their particles are widely spaced and can move freely.

Density

Density is a measure of mass per unit volume.
The density equation is: density = mass / volume.
Density can be measured for regular and irregular shapes.

Energy Transfer

There are three main types of energy transfer: conduction, convection, and radiation.
Heat travels through conduction, convection, and radiation.
A hot drink in a room loses heat, decreasing the temperature, while a cold drink gains heat, increasing the temperature.
Infrared radiation is a type of electromagnetic wave.
Electromagnetic waves, including infrared radiation, can travel through a vacuum.

Infrared Radiation

The hotter the object, the more infrared radiation it emits.
We use thermographic cameras or thermal imaging devices to see infrared radiation.
The type of surface affects how much infrared radiation it absorbs or radiates.
Different surfaces are used for different purposes, depending on their ability to absorb or radiate infrared radiation.

Conduction

Conduction does not need particles, so it can travel through a vacuum.
Conduction works best in solids, where particles are closely packed.
Conduction works worst in gases, where particles are widely spaced.
In a solid, particles pass energy through direct collisions.
Metals are fantastic conductors because of their free electrons.
Bad conductors are called insulators.
Conduction can be reduced by using insulators, increasing the distance between particles, or decreasing the temperature difference.

Heat Loss

Factors affecting heat loss include temperature difference, surface area, and insulation.
The bigger the temperature difference, the faster the heat loss.
Animals' ears help reduce heat loss by minimizing exposed surface area.
Roofs, windows, walls, floors, and doors can be insulated to reduce heat loss.
The humble draught excluder helps reduce heat loss by blocking cold air.

Energy Efficiency

Payback time is the time it takes for an investment to pay for itself through energy savings.
The payback time equation is: payback time = cost / annual energy savings.
The sooner the insulation pays for itself, the better the investment.

Energy Types

Energy types include chemical, kinetic, gravitational potential, elastic potential, internal, thermal, and nuclear energy.
Energy is conserved, meaning it cannot be created or destroyed, only converted from one type to another.
Energy pathways include conversion from one type to another, such as from kinetic to thermal energy.

Energy Efficiency and Friction

Friction can be reduced by using lubricants, streamlining shapes, or using bearings.
Wasted energy is the energy lost as heat or sound due to friction or other inefficiencies.
Useful energy is the energy that is transferred or converted into a useful form.
The efficiency equation is: efficiency = useful energy / total energy.
The power, energy, and time equation is: power = energy / time.
Power tells you the rate at which energy is transferred or converted.

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