Chemistry P2 (Page 72-80)

They are similar to most metals; they are good conductor of electricity and heat. Also, they are shiny when freshly cut. 

However, compared to most metals, they are soft and have low melting points. 

Examples of Alkali metals (reacting w/ H2O): 

Lithium: Fizzes Steadily.

Sodium: Melts into a ball, due tot eh heat produces during the reaction and fizzes rapidly. 

Potassium: Sparks present. Hydrogen produced burns with lilac flame 

(The alkali metals react with water & produce (ALKALI METAL)-OXIDE e.g. Potassium oxide & H2 Gas) 

The main Halogens are: 

Flourine - Fl2 - gas at room temperature - colour: pale yellow 

Chlorine - Cl2 - gas at room temperature - colour: yellow - green 

Bromine - Br2 - liquid at room temperature - colour: red- brown 

Iodine - I2 - solid at room temperature - colour: dark- grey 

As you go up Group 7, the reactivity increases.

As you go down the melting/boiling point increases as well as the strength of the intermolecular forces, so they would need more heat energy for the force to break. This is why it is less easier for Bromine to react than Flourine. 

PS. To test for chlorine, you need damp blue litmus paper, which turns red in the prescence of Cl2, then bleached white!!!! 

Halogens react with metals to form METAL HALIDES.

For example: 

sodium  + chlorine -> sodium chloride  (Sodium bruns with an orange flame to form white sodium chloride - Table salt :))

Another example: 

Iron + chlorine -> Iron Chloride ( which is dark- purple ) 

A Halogen atom reacts with another element and gains one electron to fill its outer shell. The harder it is for a halogen to gain an electron, the LESS REACTIVE IT IS!!

As you go down  group 7, the shells get further away from the nucleus.

So the force of attraction between the positive 'nucleus' and electrons becomes weaker.

This makes electrons less easier to gain.

So they become less reactive.

You can demonstrate a displcement reaction by reacting a Halogen solution with a Metal Halide solution, then seeing if it darkens. 

For example: 

Reacting chlorine 'water' with sodium bromine in a beaker, caused the bromine to be displaced, forming a reddish- brown solution,  Sodium chloride + BROMINE (displaced). 

This is  redox reaction. 

A REDOX REACTION IS WHEN AN ELECTRON FROM ATOM MOVES TO ANOTHER AND IS RECIEVE BY ANOTHER ATOM. 

This is called Oxidation and Reduction.

OIL RIG (Oxidation is Loss of electrons, Reduction is gain of electrons). 

So the ionic equations would be: 

Cl2 + 2e- --> 2Cl-    and         2Br --> Br2+ 2e-

The Noble Gases are ALL in Group 0, they are inert  (which means they are unrective), which mkes them very useful. 

Examples of Noble Gases and their USES:

Helium - Helium is less dense than air therefore it is used in prty balloons and airship, to allow them to flot or not be weighed down too much. 

Argon/ Krypton/ Xenon - Can all be used in filament lamps, to prevent the metal filament from burning up. They would not react with the metal, like air because they are inert

Argon - Can be used as a sheild gas during weilding, to seperate the metal from the air 

As you go down the group the densities increase, this is why you cannot use Argon or Krypton in party balloons as they are more denser than air. But you can use Helium and Neon. 

What affects Rate of Reactions: 

- Temperture - The higher the temperture,  the more the particle move and the more  likely they are to collide in one another 

- Surface area: Volume - a Larger surface area, increases rate of reaction. Rememeber when you crush up a crisp, it would have  larger surface area as it would be more exposed to other particles. 

- Catalyst - A catalyst can speed up chemical reactions without being used up in the process and limits the amount of activation energy needed for a reaction to undergo. Eg. cars need catalyst converters (paldium and platium), which converts harmful gases into harmless gases. They are expensive, but once bought they do not need to be bought again, as they are not used up.

- Concentration - A greater amount of particles or concentration, increase the chances of collision between particles 

- Pressure - in increase in pressure, causes more collisions, therefore an increase in rate of reaction 

 Have a read and turn card over and try to recall

Large Marble Chip, Powdered Marble Chip (both the same mass), a Basin, a cylinder, A conical flask, Hydrochloric Acid, Bung and a tube. 

Pour HCl Acid into the conical flask (the same amount for both experiments), then connect tube on the side of the conical flask, where there is a hole. Add some water into the basin, and place the cylinder in it. Then life the clylinder and carefully hold the tube under it. Ask your parter to add the Large marble chips and quickly put the bung on top of the conical flask. Every 10 seconds, record the volume of the oxygen bubbling through the tube, into the water. Repeat this for the powdered marble chips. The powdered marble chips should rect faster as it has a larger surface area; more of its particles are exposed to other particles. 

 Temperature changes:

Exothermic reactions: This is where heat energy is being given out to the surrouding (so the energy chnage is negative). The surroundings temperature increases. Activation energy can be supplied to this type of reaction, by applying a flame/spark (heating the reaction).

Endothermic reactions: This is where heat energy is been taken in from the surroundings (making energy change positive). The surroundings temperatures decreases. Activation energy supplied by:flowing electric current through electrolyte/continuously heating reaction

What are the main difference between these two? 

Exothermic reactions, reactant has more energy than its product, whilst endothermic reactions is the oppoiste. This is because Exothermic reactions give out heatenergy to surroundings, so there is less energy at the end result. 

On a energy profile diagram, you can find the activation energy by looking at the reactant energy the peak. Also, you can find the amount of energy given in/ out, by finding the difference between the reactant and the product.

Calcium chloride added to water and stirred. 

Explain why the mixture warms up. 

An exothermic chnage happens. More heat energy is released  forming bonds in the products than is needed to break bonds in the reactants. So overall heat energy is being given out. 

If this was an endothermic change, then the heat energy would be taken in, because less heat energy is released making bonds in the product than is needed to break bonds in the reactant. 

Crude Oil is a complex mixture of hydrocarbons, with their carbon atoms in chains or rings. It is a finite resource (meaning the production does not match the rate it is been used up at, so it could soon finish). It is also very useful, as it can be used a fuel and as feedstock in petrochemical industry. 

Hydrocarbons are compounds made up of only carbon and hydrogen. Carbon can form 4 covalent bonds, with itself or hydrogen (C-C or C-H). 

Fractional Distillation: Crude Oil can be made useful, through Fractional Distillation, as the hydrocarbons have different boiling points. So oil is used to heat it and the vapours rise in the fractional column. There is a temperature gradient so the hot is at the bottom, cold at the top. 

Boiling Point, Viscosity and Ease of Ignition depends on the amount of Carbon and Hydrogen atoms in each hydrocarbon chain. So more C and H atoms, means a higher boiling point, less easy to ignite and more viscous.