Physics Flashcards
What are the properties of Solids?
Fixed volume
Fixed shape
What are the properties of Liquids?
Fixed volume
Takes shape of the container
What are the properties of Gases?
Expand to fill container
Take shape of container
What does a Particle diagram look like for a Solid?
What does a particle diagram for a Liquid look like?
What does a particle diagram for a Gas look like?
Describe the particles of a Solid
Close together
Held in fixed positions by strong forces
Describe the particles of a liquid
Close together
Held by fairly strong forces
Can move around
Describe the particles of a Gas
Far apart
Held by very weak forces
Can move around
How do you calculate density?
Density can be calculated using this formula:
density = mass
volume
What are the units for density?
g/cm3 or kg/m3
Substances can change state when they are heated or cooled. What are the three states of matter?
Solid, Liquid and Gas
Describe/draw/label a changes of state diagram
What can be said about the melting point and the freezing point of a substance?
They are the same temperature.
The temperature of a substance does not change while it is melting, even if it is still being heated.
What happens to a substance when it is heated? Describe how this affects the particles in Solids, Liquids and Gases.
It expands.
The particles in a Solid vibrate more and take up more space.
The particles both Liquids and Gases move around faster and take up more space.
When a material expands, does the density increase or decrease?
It decreases.
What happens to a substance when it cools down? Describe how this affects the particles.
Substances contract when the coold down.
As particles have less energy they do not move as much. This reduces the volume and increased the density.
When a liquid freezes and becomes a solid, what happens to it’s density?
It increases a lot.
Why is ice unusual with regards to density?
Because it is LESS dense than liquid water. This is why ice floats on water.
Which 2 properties are fluids?
Both gases and liquids are fluids.
Describe the pressure in fluids.
Fluids can flow.
Pressure in fluids acts in all directions.
The particles in fluids are moving all the time and hitting the walls of containers and other things they come into contact with.
The force of the collisions causes pressure, which acts in all directions.
The pressure of gas in a container can be increased by: ?
Putting more particles into the container
Heating the gas
Reducing the volume of the container.
As you go deeper in the sea, what happens with the pressure?
Pressure increases because there is more water above you pressing down.
If you climb a high mountain, what happens with the pressure?
The air pressure on you will get less, because there is less air above you pressing down.
How can you decid if something will float or sink?
By working out its density, and the density of the fluid. If the density of the object is less than the density of the fluid, it will float.
What is the density of water and which objects will float in water?
The density of water is 1g/cm3, so objects with densities less than 1g/cm3 will float in water.
What is another name for air or water resistance?
Drag.
How can the amount of drag on something be reduced?
By giving it a smooth surface and a streamlined shape.
When does the drag increase?
As the speed increases
What happens to fuel consumption of cars when they are travelling fast
They use up more fuel per km
Describe how drag is caused and what happens
Drag is caused by particles in the fluid hitting the moving object and by the force needed for the object to push the fluid out of the way. The particles transfer energy to the object which is why objects moving through air can get hot.
Describe how light travels
Light travels in straight lines from a source. Light travels as transverse waves. It travels much faster than sound, and does not need a substance to travel through.
Describe what light travels through
Light travels through transparent objects but not through opaque objects.
How are shadows made?
Shadows are made when light is blocked by an object.
What objects affect light travelling through?
Opaque objects block all light.
Translucent objects allow some light to pass through but it is scattered so you do not see a clear image.
Describe Transmission and Absorption of light
Transparent materials let light pass straight through. We say they transmit light.
Opaque surfaces can absorb or reflect light.
What colour surfaces reflect, and what colour absorb most of the light?
White surfaces reflect most of the light that hits them.
Black surfaces absorb light very well and reflect very little. This is why they look so dark.
Describe diffuse reflection
This is where light rays are scattered by rough surfaces which means that you cannot see an image in an object with a rough surface.
Describe specular reflection
Mirrors and shiny materials such as polished metals reflect light evenly. This is called specular reflection.
With regards to reflection, what is the angle of incidence? And what is this known as?
The angle of incidence is equal to the angle of reflection.
This is known as the law of reflection.
In reflection how are angles measured?
Angles are measured between the light rays and the normal (a line drawn at right angles to the reflecting surface)
Why can you see an image in a mirror? And describe the image in a plain mirror.
Becasue the reflected rays of light appear to come from a point behind the mirror.
The image in a plain mirror is the same size as the object, and the same distance away from the mirror. In the image, left becomes right and right becomes left.
What is refraction?
This is when light hits something transparent and changes speed and direction.
Where does refraction take place?
At the interface between two substances.
With regards to the subject of light, what is the normal?
A line drawn at right angles to the reflecting surface.
Dwscribe what happens to light transmitted through glass.
When it is transmitted it slows down and changes direction towards the normal. When it travels back out it speeds up again and changes direction away from the normal.
What are lenses and what are they designed to do?
Lenses are curved pieces of glass or transparent plastic that are designed to refract light in particular ways.
Describe what is meant by Converging Lenses
Converging lenses make rays of light come together.
What is the focal point of a lens
The point where parallel rays of light are brought together by the lens.
What is the focal length?
The distance of the focal point from the centre of the lens.
Name three places where lenses are used
In cameras, microscopes and telescopes.
Label a diagram of a camera lens refracting light.
Label an eye lens diagram showing refraction
What do rod cells in our retinas detect and what can’t they detect?
Detect faint light but not colours
What do cone cells in our retinas detect?
They detect the primary colours of red, blue and green. We see combinations of primary colours as secondary colours (magenta, cyan and yellow).
What is white light with regards to colour?
White light is a mixture of colours.
How can we split up white light?
Using a prism to give a spectrum of seven colours (red, orange, yellow, green, blue, indigo, violet).
What is the name given to the splitting of colour into a spectrum?
It is called dispersion.
How are we able to see colours of an object?
Because objects do not reflect all the colours in light.
What colour objects reflect all the colours?
White
What colours do red objects reflect? What about other colour objects?
Red only. All the other colours are absorbed. This idea applies to all colours except black which absorbs all colours.
What are used to make coloured light?
Filters
How do filters work?
They transmit one of the colours in white light and let the other colours through.
What happens if you look at a coloured object in coloured light?
It’s colour may appear to be different.
Energy and Temperature.
What does the temperature of something tell us? And what does it not tell us?
It tells us how hot it is, not how much internal energy (thermal energy) is in it.
What is temperature measured in?
Degrees celsius (oC)
What is internal (thermal) energy measured in?
Joules (J)
The amount of thermal energy stored in something depends on what three things?
- How hot it is (its temperature)
- The material it is made from
- Its mass.
What will happen to the energy when two objects are at different temperatures?
Energy will be transfered from the hotter one to the cooler one until they are at the same temperature.
Name the 4 ways that Energy can be transferred by heating
- Evaporation
- Conduction
- Convection
- Infrared radiation
Explain evaporation
Evaporation can take place from a liquid at any temperature. When part of a liquid evaporates, it is the fastest-moving particles that escape to form a gas. The particles that are left are storing less energy as movement and so the temperature of the remaing liquid is lower.
Explain conduction
Conduction takes place in solids and can also happen in liquids (although not very well). The particles in a solid are held together tightly. When they gain energy they vibrate faster and further, and the vibrations are passed on.
Metals are the best conductors. Most other solids are poor conductors.
Particles are not as close in a liquid, so conduction is not very good.
Particles are a long way apare in gases, so gases hardly conduct heat at all.
What are the best conductors?
Metals
Is conduction good in liquids and why?
No because particles are not so close.
Is conduction any good in gases and why?
No, because particles are a long way apart in gases, so gases hardly conduct heat at all.
What do we call something that does not conduct heat very well?
A thermal insulator.
What term is given to liquids, gases, and solids that contain a lot of trapped air?
Insulators
Explain convection
Convection takes place in fluids (liquids and gases). When part of a fluid is heated, the particles spread further apart and the fluid becomes less dense. This makes it ris. As it rises it meets cooler fluid and passes the energy on. Moor cool fluid moves in to replace the rising fluid, setting up a convection current.
Describe infrared radiation
Infrared radiation can transfer energy through empty space and also through transparent materials. Radiation does not require the movement of particles. Any hot or warm object gives off or emits radiation. When something takes in energy from radiation, it is said to absorb it.
It is similar to light. It can be absorbed or reflected, and it can also be focused.
Dard, dull surfaces are good emitters and absorbers of radiation. Light, shiny surfaces are good at reflecting radioation. The are poor absorbers of radiation.
What is Power?
The rate at which energy is transferred.
What is power measured in?
Watts (W) or kilowatts (kW).
1000W = 1kW
What is Efficiency
Not all energy is transferred usefully. Wasted energy is often transferred by heating. The percentage of useful energy produced by something is known as its effeciency.
What formula is used to calculate energy efficiency?
efficiency = useful energy transferred / total energy supplied x 100%
What type of diagram would be used to show the energy transfer in a kettle and what does it show?
A Sankey diagram. The width of each arrow shows the amount of energy it represents. The energy stored in the kettle and the surroundings is wasted energy.
We pay for the energy used in our homes. Electricity companies use units of kilowatt-hours on electricity bills. What does One kilowatt-hour mean?
It is the energy transferred when a one kW appliance is used for one hour.
How can we reduce energy bills in our homes?
By insulating our homes and by using more efficient appliances.
What is the payback time in regards to installing something that makes a home more energy efficient.
It is the time taken for the cost of installation to be matched by the money save. Sometimes buyin a more efficient appliance may not save you energy overall because it costs more to buy than it will save.
Payback time = cost of change/savings per year.
When is a measurement classed as accurate?
When it is close to the true value of the thing being measured. Measuring devices that have small divisions can measure more accurately than instruments with larger divisions if they are set up correctly.
When is a measurement classed as precise?
If several measurements of the same thing give similar results. Precise measurements may not be accurate if the measuring instrument was not set up correctly.
Where does Earth get energy from?
The Sun
How often does the Earth spin on its axis?
Once every 24 hours.
Which side of the Earth has daylight and where is the night?
The side of the Earth facing the Sun has daylight and it is night on the side facing away from the Sun.
The Earth orbits around the Sun. How long does it take to go around once?
One year.
What is Earth’s only naturally satellite?
The moon
Why can we see the Moon?
Because it reflects light from the Sun.
The Moon seems to change shape. What are the different shapes called?
Phases of the Moon
Why do the phases of the moon happen?
Because we cannot always see all of the part that is lit by the Sun.
How many planets are in elliptical (oval shaped) orbits around the Sun.?
Eight.
What makes up the Solar System?
The Sun, the planets and their moons make up the Solar System
The eight planets names are: ?
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
Why is it hotter in the summer with longer days than nights and the Sun higher in the sky?
Because the Earth’s axis is tilted. When the northern hemisphere is tilted towards the Sun it is summer in the UK. The Sun’s rays are more concentrated, so it feels hotter.
What type of materials do Magnets attract?
Magnetic materials
What are the two ends of a bar magent called?
The north-seeking pole and the south-seeking pole, or north pole and south pole for short.
On a bar magnetic which two poles attract each other?
A north pole and a south pole attract each other
On a bar magnet what do two north poles or two south poles do to each other?
They repel each other
What is the name given to a space around a magnet where it has an effect?
Magnetic field
How can you find the shape of the magnetic field?
By using iron filings or a plotting compass
What is the mass of something? And what is it measured in?
The mass of something is the amount of substance or ‘matter’ it contains. It is measured in kilograms (kg).
In the subject of Gravity and gravitational fields, what is the weight and what is it measured in?
Weight is the force of gravity pulling on a mass. It is a force, so it is measured in newtons (N).
What is Gravity?
The force of attraction between two masses.
When is the force of gravity stronger?
- If the objects have large masses
- If the objects are close together
On Earth, what force (how much) in Newtons (N) does gravity pull on every kilogram of mass?
On Earth, gravity pulls on every kilogram of mass with a force of about 10N
Where is gravity not as strong and why?
Gravity is not as strong on the Moon because the Moon has a much smaller mass than the Earth.
If you went to the Moon what would happen to
- your mass
- your weight
and why?
If you went to the Moon your mass would not change, but your weight would be less than on Earth because the Moon’s gravity is weaker.
What formula do we need to calculate the weight of an object?
weight (N) = mass (kg) x gravitational field strength (N/kg)
The Sun’s gravity keeps all the planets in our Solar System moving how/in what way?
in elliptical orbits around it.
If there was no gravity from the Sun, what would happen to all the Planets?
They would all fly off into space.
Which planet’s gravity keeps the Moon in orbit around it?
Earth
What is a satellite?
Anything that orbits around a planet.
What is the only natural satellite of the Earth?
The Moon
Artificial satellites are put into orbit around the Earth or other planets. What can they be used for?
Taking pictures or transmitting TV programmes.
Planets do not make their own light. Why can we sometimes see the planets?
Because they reflect light from the Sun.
What is the Sun and what does it give out?
It is a star. It is a ball of gas that gives out large amounts of energy.
Why do the stars not look very bright?
Because they are further away than the Sun.
What name is given to the patterns that stars are often grouped into?
Constellations
The Sun is one of millions of stars in our galaxy. What is our galaxy called?
The Milky Way.
Complete the sentence…
There are millions of galaxies in the…………………..
Universe
What do Scientists measure distances to the stars using?
Light years.
What is a light year?
The distance that light can travel in one year.
