Elements are made of only one element, e.g. O2 is two oxygen atoms bonded together. Different elements are defined by their number of Protons.
Compounds are different elements chemically bonded, i.e. more that one element chemically joined e.g. H2O is two hydrogen atoms and one oxygen atom chemically joined.
Mixtures are different chemical compounds or atoms mixed together but not chemically joined to one another
Sunday, 3 May 2015
Wednesday, 8 April 2015
1.5 Understand the difference between the terms atom and molecule
An atom = the smallest particle of a chemical element that can exist
A molecule = a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
(both definitions from Google)
A molecule = a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.
(both definitions from Google)
1.4 Describe and explain experiments to investigate the small size of particles and their movement
I) dilution of coloured solutions
Dilution is when you add something to a mixture of a substance, meaning that the total fraction of the original substance out of the whole mixture is decreased. This is a very long, confusing definition, but usually it will be in the context of a solution, where more solvent is being added.
For example: Say you have 3g table salt (NaCl) dissolved in 20ml of water. As 20ml distilled water weighs 20g, the overall weight of the solution would be 23g. This means that 3/23g was salt. If you diluted the substance by adding 40ml distilled water, the slat would now be 3/63g of water.
There is a technique for trying to figure out the mass of substances using dilution, but it is very inaccurate.
Suppose you dissolve 0.1g of potassium manganate in 10ml of water to get a purple solution.
You could then dilute this by 10 times by taking 1ml of the solution and mixing it with 10ml more water. Continue doing this process until the colour is too faint to see. Perhaps you could see the purple colour still after 5 dilutions but not 6.
By the time of the fifth dilution, each 0.001ml drop would only contain a billionth of a gram of potassium manganate. If you only need one 'particle' of potassium manganate per drop in order to see the colour, the 'particle' can't weigh more than a billionth of a gram.
This is not a very good answer: The 'particle' actually weighs 0.00000000000000000000026g! But the textbook seemed to think that this technique was important to know.
ii) Diffusion experiments
Diffusion is the intermingling of substances by the natural movement of their particles. Diffusion experiments can be set up to see which substances have a greater mass.
An example of an experiment is the one above. If a substance diffuses faster than another substance, then it weigh less. The ammonia diffused faster that the HCl, as it got further before it met and reacted with the HCL.
Dilution is when you add something to a mixture of a substance, meaning that the total fraction of the original substance out of the whole mixture is decreased. This is a very long, confusing definition, but usually it will be in the context of a solution, where more solvent is being added.
For example: Say you have 3g table salt (NaCl) dissolved in 20ml of water. As 20ml distilled water weighs 20g, the overall weight of the solution would be 23g. This means that 3/23g was salt. If you diluted the substance by adding 40ml distilled water, the slat would now be 3/63g of water.
There is a technique for trying to figure out the mass of substances using dilution, but it is very inaccurate.
Suppose you dissolve 0.1g of potassium manganate in 10ml of water to get a purple solution.
You could then dilute this by 10 times by taking 1ml of the solution and mixing it with 10ml more water. Continue doing this process until the colour is too faint to see. Perhaps you could see the purple colour still after 5 dilutions but not 6.
By the time of the fifth dilution, each 0.001ml drop would only contain a billionth of a gram of potassium manganate. If you only need one 'particle' of potassium manganate per drop in order to see the colour, the 'particle' can't weigh more than a billionth of a gram.
This is not a very good answer: The 'particle' actually weighs 0.00000000000000000000026g! But the textbook seemed to think that this technique was important to know.
ii) Diffusion experiments
An example of an experiment is the one above. If a substance diffuses faster than another substance, then it weigh less. The ammonia diffused faster that the HCl, as it got further before it met and reacted with the HCL.
1.3 Explain the changes in arrangement, movement and energy of particles during these changes
As particles, for example in a liquid, are heated, they gain thermal energy, which is then transferred into kinetic energy. This means that the liquid would move more and more rapidly until it reaches the point where the increased energy causes it to evapourate and become a gas.
The reverse is true: if a liquid is cooled, it looses energy, so it does not move about so much. It stays in a fixed position and becomes a solid.
The reverse is true: if a liquid is cooled, it looses energy, so it does not move about so much. It stays in a fixed position and becomes a solid.
1.1 Understand the arrangement, movement and energy of the particles in each of the three states of matter: Solid, Liquid and Gas
Particles in solids touch all touch and are in fixed positions. They have very little energy and only vibrate in their fixed positions.
Particles in liquids touch as well, but they are not in fixed positions; they can slide over one another. They have more energy than solid, which is why they move more.
Particles in gases do not touch but are spread out to fill the container in which they are held. They have much more energy, and move randomly.
Particles in liquids touch as well, but they are not in fixed positions; they can slide over one another. They have more energy than solid, which is why they move more.
Particles in gases do not touch but are spread out to fill the container in which they are held. They have much more energy, and move randomly.
1.2 Understand how the interconversions of solid, liquids and gases are acheived and recall the names used for these three interconversions
Solid to liquid = Melting
Liquid to gas = Evapouration
Gas to Liquid = Condensation
Liquid to Solid = Solidification (sometimes Freezing)
Solid to Gas or Gas to Solid = Sublimation (e.g. Carbon Dioxide)
Liquid to gas = Evapouration
Gas to Liquid = Condensation
Liquid to Solid = Solidification (sometimes Freezing)
Solid to Gas or Gas to Solid = Sublimation (e.g. Carbon Dioxide)
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