Physics P6

  • Created by: katyh67
  • Created on: 04-12-18 18:12

Density facts

To find the density you perform this equation: mass/volume

Facts:

- a density depends on what the object is made of

-A dense material has its particles packed tightly together. So, the particles in a less dense material are more spread out- if you compressed the material its particles would move closer together and it would become more dense.(you wouldn't be changing its mass but you would be decreasing its volume)

-Solids are denser than liquids, liquids are denser than gases.

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To find the density of an irregular object

1. Find the mass by weighing the object

2. Get a eureka can and fill it with water, just above the spout whilst your finger is covering the spout. Once you have filled it up lift you finger from the spout so there is an accurate and reliable measurement of water.

3. Place a measuring cylinder underneath the eureka can

4. Plce the irregular object into the can so that water will be pushed upwards and be poured into the measuring cylinder.

5. Calculate volume from the amount of water displaced

6. Calculate density(mass/volume)

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To find the density of a liquid

1. Place a measuring cylinder on the balance and zero the balance

2. Pour 10ml of the liquid into the measuring cylinder and record the liquid's mass.

3. Pour another 10ml into the measuring cylinder and record the total volume and mass.

4. Repeat this process until neasuring cylinder is full

5. For each measurement find density

6. Finally take an average of your calculated densities to get an accurate value for the density of the liquid.

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Latent heat

There are two types of latent heat:

-Latent heat of fusion(amount of heat needed for a solid to melt)

-Latent heat of vaporisation(amount of heat needed for a liquid to boil)

Thermal energy for a change of state(J) = mass(kg) x specific latent heat(J/kg)

Specific latent heat(fusion)- amount of energy needed for 1kg of the solid to melt

Specific latent heat(vaporisation)- amount of energy needed for 1kg of a liquid to boil

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Internal Energy

-Increasing the temperature of a substanceincreases its internal energy.

-The strength of the forces of attraction explains why it is a solid, liquid or a gas

-When a substance is heated: if its temperature increases, the kinetic energy of its particles increases.

-If it melts or boils, the potential energy of its particles increases

-The pressure of a gas on a surface is caused by the particles of the gas repeatedly hitting the surface.

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Particles

Solids- Strong forces of attraction, can only vibrate in fixed positions as the particles don't have much energy, high density as particles are close together and as the particles are touching, solids cannot be squashed.

Liquids- Medium forces of attraction so they can move arounf each other, move in random directions at low speeds, less dense than solids but denser than gases and the particles are touching,so liquids cannot be squashed.

Gases- Almost no forces of attraction, Gases can fill any container as the particles move about since they can move freely due to enough energy and as there is space between the particles, they can be squashed into a smaller volume when the gas is compressed.

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Can liquids fill the whole container?

Liquids can't fill the whole container as it only fills the bottom of the container since the particles don't have enough energy to move freely.

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Kinetic theory

At the boiling point:

-a liquid turns into a gas

-a gas turns into a liquid

At the melting point:

-a solid turns into a liquid

-a liquid turns into a solid

Summary:

-compressing a gas heats it up

-condensation causes heating

-expanding a gas cools it down

-evaporation causes cooling

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Specific heat capacity

The amount on energy required to increase the temp of 1kg of any material by 1^c

Different materials have different specific heat capacitys

Energy(J) = Specific heat capacity(J/kg/*c) x mass(kg) x change in temperature(*c)

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Method for the coins(specific heat capacity)

1. pour boiling water into a large beaker and place a thermometer in

2. start to put cold water in the beaker until it is no longer boiling and is 30 degrees celcius 

3. Next, use a measuring cylinder to measure 100ml of the water

4. pour the water into a polystyrene cup(put it into a large beaker for support)

5. place 4 cold copper coins(brass) into the cupand place the lid onto the cup and wait 5 mins.

6. Check the temperature and calculate temperature change

7. Work out mass of the 4 coins

8. Work out energy from the information

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