Particle Model Of Matter Flashcards
1
Q
Describe solid state
A
- strong forces of attraction hold the particles close together in a fixed, regular arrangement
- The particles don’t have much energy so they can only vibrate about their fixed positions
- the density is generally highest in this state as the particles are closest together
2
Q
Describe liquid state
A
- there are weaker forces of attraction between the particles
- the particles are close together, but can move past each other, and form irregular arrangements
- For any given substance, in liquid state its particles will have more energy than in the solid state (but less energy than in the gas state)
- They move in random directions at low speeds
- liquids are generally less dense than solids
3
Q
Describe gas state
A
- almost no forces of attraction between the particles
- for any given substance, in the gas state its particles will have more energy than in the solid state or the liquid state
- they are free to move, and travel in random directions and at high speeds
- gases have low densities
4
Q
What is density
A
- it relates the mass of a substance to how much space it takes up
- The units of density is kg/m^3
5
Q
What is an objects density dependent on
A
- what it’s made of
- a dense material has its particles tightly packed together
- a less dense material has its particles spread out
- If you compressed the material, its particles would move closer together, and it would become more dense (it’s mass doesn’t change, but it does decrease the volume)
- Therefore density varies between states of matter
6
Q
How do you find the density of a solid object
A
- use a balance to measure its mass
- for some solid shapes you can use the formula for volume
- for an irregular shape you can find the volume by submerging it in a eureka can filled with water
- the water displaced by the object will be transferred to the measuring cylinder
- record the volume of water in the measuring cylinder. This is the volume of the object
- plug the objects mass and volume into the density formula to find the density
7
Q
How do you find the density of a liquid
A
- place a measuring cylinder on a balance and zero the balance
- pour 10ml of the liquid into the measuring cylinder and record the liquid’s mass
- pour another 10ml into the measuring cylinder and record the total volume and mass. Repeat until the cylinder is full
- For each measurement, use the formula to find the density (1 ml = 1 cm^3)
- Finally take an avg. of your calculated densities to get an accurate value for the density of the liquid
8
Q
Describe internal energy
A
- it is stored by the particles that make up a system
- It is the total energy that its particles have in their kinetic and potential energy stores
- heating the system transfers energy to its particles (they gain energy in their kinetic stores and move faster, increasing internal energy)
- This leads to a change in temp / state. If the temp changes, the size of the change depends on the mass of the substance, what it’s made of (it’s specific heat capacity) and the energy input.
- A change in state occurs if the substance is heated enough - the particles will have enough energy in their kinetic energy stores to break the bonds holding them together.
9
Q
Describe how a change of state conserves mass
A
- change of state can be brought on by temp changes
- when it cools, it looses energy and forms bond
- a change of state is a physical change. This means you don’t end up with a new substance - it’s the same substance as you started with, just in a different form
- if you reverse a change of state the substance will return to its original form and get back its original properties
- The number of particles doesn’t change - they’re just arranged differently
- This means that mass is conserved - none of it is lost when the substance changes state
10
Q
What is required for a change of state
A
Energy
11
Q
What happens when you are melting or boiling a substance
A
- you’re still putting in energy and so increasing internal energy
- but the energy is used for breaking bonds between particles rather than raising the temp
- There are flat spots on the heating graph where energy is being transferred by heating but not being used to change temp
12
Q
What happens when you are condensing or freezing a substance
A
- bonds are forming between particles
- which releases energy
- This means internal energy decreases, but temp doesn’t go down until all the substance has turned to liquid or solid.
- The flat parts of the graph show the energy transfer.
13
Q
Describe and explain what Specific Latent Heat is
A
- the amount of energy needed to change 1kg of it from one state to another without changing it’s temp
- For cooling, specific latent heat is the energy released by a change in state
- Specific latent heat is different for different materials, and for changing between different states
- The specific latent heat for changing between a solid and a liquid (melting or freezing) is called the specific latent heat of fusion
- The specific latent heat for changing between a liquid and a gas (evaporating, boiling or condensing) is called the specific latent heat of vaporisation)
14
Q
What’s the formula for specific latent heat
A
Energy (J) = Mass (Kg) x Specific Latent Heat (J/kg)
15
Q
What happens when gas particles are colliding
A
- the particles are free to move around
- they move at high speeds and bang into each other and whatever else is in their way
- When they collide with something, they exert a force on it
- pressure is the force exerted per unit area
- So in a sealed container, the outward gas pressure is the total force exerted by all of the particles in the gas on a union area of the container walls
