Particle Model Of Matter Flashcards
What is density?
The amount of mass in a set volume. It tells us how tightly packed together particles in a substance are.
How can you make an object more dense?
By decreasing the volume
By increasing the mass
Density equation
Density= mass(kg) divided by volume(m)
How to calculate density for regular shapes:
Put object on scales to find mass
LengthXheightXwidth-to find volume
Mass divided by volume to get density
How to Calculate density for irregular shapes:
Place object on scales to find mass
Measure displaced water to find volume
Properties of a solid:
The particles are tightly packed
They hold their own shape
Properties of a liquid:
The particles are touching but not tightly packed
You can pour them
Properties of a gas:
They are spread out
They do not touch
Move every direction, different speeds
What is the process called of turning a solid into a liquid?
Melting
What is the process called of turning a liquid into a gas?
Boiling/evaporation
What is the process called of turning a gas into a liquid?
Condensation
What is the process called of turning a liquid into a solid?
Freezing
What is the process of turning a solid Into a gas?
Sublimation
What is the process of turning a gas into a solid?
Desublimation
What happens to the mass of a substance as it changes state?
The mass either increases or decreases because particles are either closer or further away
What happens to the temperature of a substance as it changes state?
Heats up the substance but as it changes state, the temperature stays constant. More energy is used to break the bonds.
Properties of chemical changes:
Irreversible
New substance is formed
May see: change in colour/smell, change in temp, bubbles/ fizzing
E.g. burning, baking a cake
Properties of physical changes:
Reversible
Changes in state
E.g. boiling water, melting ice lolly
What does temperature mean?
Average (kinetic) energy per particle
What does heat mean?
The total (kinetic) energy of all particles
Why do particles have kinetic energy?
Because they vibrate or move around. They also have gravitational potential energy because of their positions in the substance
What does internal energy mean?
The internal energy of a system is the total energy that is stored by the particles (kinetic + potential)
What happens during a change of state?
During a change of state, temperature stays constant. Instead of the particles gaining kinetic energy, they energy is used to break bonds between them.
What is specific heat capacity?
The amount of thermal energy needed to raise 1kg of a substance by 1degreec
Objects with a low SHC (e.g. metals) need only a small amount of energy to heat up, so do so very quickly (and cool down very quickly)
Objects with a high SHC (e.g. water) need a lot of energy to heat up, which takes a lot longer. They also store energy for longer (cool down slowly), so are useful for heating our homes.
What do we use to heat our homes and why?
We use water, oil and gas to heat our homes. We use these because they have a high SHC so store energy for longer.
What is the energy needed for a substance to change state called?
Latent heat
What is the difference between Latent heat of fusion and Latent heat of vaporisation?
Latent heat of fusion is for melting
Latent heat of vaporisation is for melting
What is specific latent heat?
The specific latent heat of a substance is the energy required per kilogram to change its state without any change in temperature.
What causes gas pressure?
Gas (air) particles move around quickly in all directions. Eventually, they bump into something (each other, walls of a container, or objects such as people). When they hit something, they produce a force on that object which results in gas pressure.
What is Brownian motion?
When you increase the temperature, the gas moves faster because as you heat the gas, the particles gain more kinetic energy and move with greater speed. The faster they move, the more force they exert when they collide, which increases the pressure. BROWNIAN MOTION is the constant random motion of particles. It is due to collisions of larger particles (e.g.dust) with smaller, invisible ones (e.g.air)
What makes a substance radioactive?
Some substances give out radiation from their nuclei all the time- these are said to be radioactive
What are the natural sources of radiation?
Rocks (radon gas)
Food
Sun/cosmic rays
What are the man-made sources of radiation?
Medical
Nuclear power stations
Nuclear weapons
What is ionising radiation?
Ionising radiation has enough energy to remove electrons from atoms they interact with, creating ions.
Ionising radiation can damage human cells, which can lead to illness such as cancer
Properties of alpha:
It’s a helium nucleus Has 2 protons and 2 neutrons Large mass \+2 charge Penetrating power= a few centimetres of air, skin, paper Range in air=5cm Most ionising
Properties of Beta:
A fast moving electron Very small mass -1 charge Penetrating power= thin sheets of metal Range in air=1km
Properties of Gamma:
It’s an electromagnetic wave with highest frequency and shortest wavelength Mass=0 Charge=0 Penetrating power=thick lead Range in air=infinite Least ionising
What happens when a radioactive atom decays?
It releases an atom of a different element and either an alpha or beta particle (if gamma is released, the element stays the same)
How does a smoke alarm work?
uses americium-241, a source of alpha radiation, to detect smoke. The alpha radiation ionises the air particles inside the smoke detector. This allows a small electric current to flow. If there is a fire, smoke particles going into the detector are hit by alpha radiation. This reduces the ionisation of the air particles causing the current to drop. The drop in current is detected by the smoke detector, setting off the alarm
Why wouldn’t Beta and Gamma work in a fire alarm?
Because they aren’t as ionising so they wouldn’t work. Also, alpha has a 5cm range in the air so will detect smoke from 5cm away instead of from anywhere
Why is Beta used in paper thickness?
Radiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium. The thicker the material, the more radiation is absorbed and the less radiation reaches the detector. It then sends signals to the equipment that adjusts the thickness of the material.
Why is alpha and gamma useless in paper thickness?
Alpha is useless in this situation because it has a very low penetrating power
Gamma is also useless because it has too strong a penetrating power.
Why does a gamma knife use gamma radiation?
Works by passing a beam of radiation to the head. Only does damage to the bit it’s constantly aimed at (the tumour). Can’t use alpha because it won’t go through skin. Can’t use Beta because it can’t go through your skull. The beams of radiation are very precisely focused to reach the tumour, lesion, or other area treated with minimal effect on surrounding healthy tissue.
What is half life?
Average time it takes for half of the parent nuclei (the ones you start with) to have decayed into daughter nuclei (the ones they change Into).- also average time for activity to half. Radioactive decay is RANDOM
What is background radiation?
Background radiation is all around us. Some of it comes from natural sources and some comes from artificial sources.
What are the natural sources of background radiation?
Cosmic rays
Rocks and soil
Living things
What are the artificial sources of background radiation?
X-rays
Nuclear power
Nuclear missiles
What is activity?
The average rate at which a source of unstable (radioactive) nuclei decays.
Activity is measured in Becquerel(Bq) unit of activity decays per second.
Count-rate is the total number of decays recorded each second by a detector (e.g. Geiger-Muller tube)
How do you find half-life on a graph?
Half the highest number, go across the graph and follow it down to the half-life
The half-life of a particular isotope never changes
How does radioactive material spread?
If radioactive material is not in a sealed container, it might spread onto other objects. Contamination occurs when material that contains radioactive atoms is deposited on materials, skin, clothing, or any place where it is not desired. A person contaminated with radioactive material will receive radiation exposure until the source of radiation is removed
Why is the radiation dangerous?
Radiation damages the cells that make up the human body. Low levels of radiation are not dangerous, but medium levels can lead to sickness, headaches, vomiting and a fever. High levels can kill you by causing damage to your internal organs, it is difficult to treat high radiation exposure.
What does Irradiation mean?
Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources.
Objects, but also animals and people, do not become radioactive when they are exposed to alpha, beta or gamma radiation.
What are the precautions when handling radioactive materials?
Wearing protective clothing
Keeping as far away as is practicable-for example, by using tongs
Keeping your exposure time as short as possible
Keeping radioactive materials in lead-lined containers, labelled with the appropriate hazard symbol
