1- Atomic Structure and the Periodic Table Flashcards
What is the definition of an element? (ECM ASPT Ch)
In an element, all of the atoms are the same.
What is the definition of a compound? (ECM ASPT Ch)
compounds contain two or more different elements chemically bonded in fixed proportions. Compounds also usually have totally different properties to the elements that they are made from.
What is the definition of a mixture? (ECM ASPT Ch)
different elements or compounds but they are not chemically bonded together.
How do you seperate a mixture? (ECM ASPT Ch)
a physical separation techinque rather than a chemical reaction
How do you seperate a compund? (ECM ASPT Ch)
use a chemical reaction (reduction and electrolysis)
What are all of the physical seperation techniques? (ECM ASPT Ch)
- filtration
- distillation
- crystallisation
- chromatography
What is a molecule? (ECM ASPT Ch)
a molecule has any elements chemically combined. Even if they are the same element e.g O2. This is different to a compound as that has to have different elements.
Can physical separation techniques be used to separate the elements in a compound? (FaC ASPT Ch)
no. they can only be used for mixtures.
What is filtration used for? (FaC ASPT Ch)
to separate an insoluble solid from a liquid.
Describe the process of filtration: (FaC ASPT Ch)
setup: conical flask with a filter funnel in the top of it, within the filter funnel should be some filter paper.
1. pour the mixture into the filter paper
2. the liquid passes through the tiny pores in the filter paper. This liquid is called a filtrate.
3. the solid material cannot pass through the filter paper so it remains
4. Once as much of the liquid as possible has passes through, we have our liquid separated from our solid.
What is crystalisation used for? (FaC ASPT Ch)
to separate a soluble solid from a liquid.
Describe the method for carrying out crystallisation: (FaC ASPT Ch)
option one: leave the solution out for a few days until all of the liquid (water) has evaporated out. This will leave behind crystals.
option two (the faster way): gently heat the solution to evaporate the water.
What does the state symbol aq mean? (FaC ASPT Ch)
an aqueous solution
the molecule / element is dissolved in water.
Why must the solution in crystallisation be heated gently? (FaC ASPT Ch)
certain chemicals will break down if we heat them so sometimes it is better to allow the water to evaporate on its own.
What is the problem in crystallistaion? (SD ASPT Ch)
what if we want to keep the liquid? we use simple distillation
What are the two stages of simple distillation? (SD ASPT Ch)
- evaporate the liquid by heating which turns the liquid into a vapour.
- condense the vapour back into a liquid by cooling.
Describe the porcess of carrying out simple distillation: (SD ASPT Ch)
Setup: a flask is connected to a continuous glass tube. This tube is surrounded by a jacket called the condenser. Cold water from the tap is constantly running through the condenser which keeps the internal of the glass tube cold. After the condenser the cold water goes down the sink. There is a thermometre.
1. place our solution into the flask.
2. heat the solution e.g by using a Bunsen Burner
3. As we heat, the liquid starts to evaporate, turning into a vapour.
4. the vapour rises up the glass tube
5. As the vapour passes over the thermometer, the reading increases
6. normally we heat the solution until it bubbles
7. vapour passes into the condenser which causes the vapour to condense, turning back to a liquid as it passes through the condenser
8. we collect the liquid in the beaker.
we are left with solid crystals in the flask and our liquid in the beaker
What is simple distillation used for? (SD ASPT Ch)
Separating a dissolved solid and a liquid when we want to keep the liquid.
What is an example of simplie distillation in the real world? (SD ASPT Ch)
making drinking water out of sea water but a lot of energy is required for simple distillation so generally not used for drinking water.
