C2 Smart Teach 3: Alkali metals, Halogens and rates of reaction

Group 1 Elements The elements in group 1 are all called alkali metals They have one electron in their outer shell The react with water to produce hydrogen and a metal hydroxide (these are alkaline) General word equation – Can be applied to any alkali metal Metal + Water  Metal hydroxide + Hydrogen Sodium + Water  Sodium hydroxide + Hydrogen General symbol equation – the balancing can be applied to any alkali metal 2M + 2H 2 O  2MOH + H 2 2Na + 2H 2 O  2NaOH + H 2

Group 1 elements a)Describe what you would see when a group 1 element reacts with water b) Why does the metal float? fizzing, metal floats, moves round surface of water, metal melts and then disappears. The heat melts the metal as it has a low melting point, because it has a lower density than water it floats

Group 1 Elements Describe and explain the trend in reactivity of group 1 elements as you go down the group! Group 1 metals become more reactive down the group This is because as you go down the group there is an increased number of shells This leads to increased shielding therefore it is easier to loose outer electron.

Group 8/0 Elements The elements in 8/0 are called the Nobel Gases The Nobel gases have a variety of uses, what property determines their uses? They are inert (unreactive) they have a full outer shell, the are used in light bulbs

Group 7 elements Group 7 metals are called the halogens HalogenState at room temperature Colour FluorineGasYellow – Green ChlorineGasYellow BromineLiquidBrown IodineSolidGrey

Group 7 elements Halogens get less reactive as you go down the group Key term: Halide = a halogen joined to a metal e.g NaF When a metal halide reacts with a halogen this is called a displacement reaction. A reaction will only occur if the halogen in more reactive than the halide.

Group 7 – Can you complete these equations

Group 7 Halogens react with hydrogen to form hydrogen halides General word equation – can be applied to any halogen Hydrogen + Halogen  Hydrogen halide Hydrogen + Chlorine  Hydrogen Chloride General Symbol equation – Can be applied to any halogen H 2 + X 2  2HX H 2 + Cl 2  2HCl

Rates of reaction Factoreffect on rate of reaction explanation Use a higher temperature Speeds up reactionParticles move faster, more frequent collisions, particles have more energy, more successful collisions. Faster rate Use smaller piecesSpeeds up reactionLarger surface area, more frequent collisions, faster rate of reaction Use a higher concentration Speeds up reactionMore particles, more frequent collisions, more successful collisions, faster rate

Explain the meaning of the term catalyst Why do we use catalytic convertors increases rate of reaction without being used up its self speeds up reaction of carbon monoxide with oxygen, prevents harmful gases from entering the air

Rate of reaction In many questions you are asked to describe how you would carry out a rates investigation. For example “how the surface area of calcium carbonate affects the rate of a chemical reaction when reacted with HCl” In these questions your need to: give volumes used, masses used, method to collect gas, size of chips, method to time, a second experiment with same details that would test the hypothesis., what results would show. Easiest method to remember for collecting gases = Gas Syringe

Rates of Reaction 4)Look at this graph of volume of gas produced over time when magnesium powder was reacted with hydrochloric acid a)If I increase the temperature I get the line “X”  Rate is faster same amount of gas produced b)If I increase the concentration of the acid I get line “Y”  Rate is faster and more gas is produced because there was more acid to react c) If I use magnesium ribbon instead of powder get line “Z”  Rate is slower, same amount of gas is produced X Y Z Time Vol of gas