Hydroxides & OxidesHydroxides & Oxides

D. Crowley, 2007D. Crowley, 2007

Hydroxides & OxidesHydroxides & Oxides

To be able to describe the reaction To be able to describe the reaction between metals + water and metals + between metals + water and metals + oxygenoxygen

Metal or Non-metal?Metal or Non-metal?

Using the sheet, cut out Using the sheet, cut out the summary for metals the summary for metals & non-metals& non-metals

Stick these into your Stick these into your booksbooks

Metals & Non-metalsMetals & Non-metals

MetalsMetals: conduct electricity; conducts heat well; is : conduct electricity; conducts heat well; is malleable, I.e. can bend without breaking; is malleable, I.e. can bend without breaking; is usually a hard material; has strong forces usually a hard material; has strong forces between atoms which are very close togetherbetween atoms which are very close together

Non-metalsNon-metals: does not usually conduct electricity; : does not usually conduct electricity; does not conduct heat well; is brittle and not does not conduct heat well; is brittle and not strong; usually has a low melting point; has strong; usually has a low melting point; has weak forces as the atoms are not very close weak forces as the atoms are not very close togethertogether

ReactionReaction

Today you are doing an experimentToday you are doing an experimentYou are going to see what happens when You are going to see what happens when

you react some metals with warm wateryou react some metals with warm water

You’ll be testing for hydrogen, and You’ll be testing for hydrogen, and identifying the pHidentifying the pH

ExperimentExperiment

You will need a Bunsen burner (on the You will need a Bunsen burner (on the safety flame)safety flame)

A heat-proof matA heat-proof matSome splintsSome splintsA boiling tube (half filled with water)A boiling tube (half filled with water)1 piece of magnesium, calcium & copper1 piece of magnesium, calcium & copper

ProcedureProcedure

Place one of the metals in the boiling tube, Place one of the metals in the boiling tube, and heat gentlyand heat gently

After a short while light a splint, and place After a short while light a splint, and place this in the end of the boiling tube - has this in the end of the boiling tube - has hydrogen been produced - how will you hydrogen been produced - how will you know?know?

Finally, add a few drops of UI in, and Finally, add a few drops of UI in, and record the pHrecord the pH

FindingsFindings

Hopefully you found that when some metals Hopefully you found that when some metals were placed in water they reactedwere placed in water they reacted

Hydrogen was produced (squeaky pop)Hydrogen was produced (squeaky pop) The pH also changed - it went from neutral to The pH also changed - it went from neutral to

alkaline (purple)alkaline (purple)

However not all the metals react - so some are However not all the metals react - so some are reactive, others are notreactive, others are not

Watch the demo of some very reactive metals…Watch the demo of some very reactive metals…

Key PointKey Point

When a When a metalmetal reacts with water, it produces a reacts with water, it produces a metal hydroxidemetal hydroxide + + hydrogenhydrogen

metalmetal + + waterwater metal hydroxidemetal hydroxide + + hydrogenhydrogen

EquationsEquations

Some metals react with water, forming a hydroxide and Some metals react with water, forming a hydroxide and releasing hydrogen…releasing hydrogen…

The copper did not do anything in the water (no reaction)The copper did not do anything in the water (no reaction)

The magnesium did not do much in the water - you may The magnesium did not do much in the water - you may have got a slight pop (slight reaction)have got a slight pop (slight reaction)

The calcium was more reactive in the water - it produced The calcium was more reactive in the water - it produced a squeaky pop (stronger reaction)a squeaky pop (stronger reaction)

EquationsEquationsRemember: Remember: metalmetal + + waterwater metal hydroxide + metal hydroxide + hydrogenhydrogen

CalciumCalcium + + WaterWater Calcium hydroxideCalcium hydroxide + + HydrogenHydrogen

CaCa (g) + (g) + 2H 2H22OO (l) (l) Ca(OH)Ca(OH)22 (aq) + (aq) + HH22 (g)(g)

MagnesiumMagnesium + + WaterWater Magnesium hydroxideMagnesium hydroxide + + HydrogenHydrogen

MgMg (g) + (g) + 2H2H22OO (l) (l) Mg(OH)Mg(OH)22 (aq) + (aq) + HH22 (g)(g)

ReactivityReactivity

So, some metals are un-reactive in water - such So, some metals are un-reactive in water - such as copper and goldas copper and gold

This is why copper pipes at great at carrying This is why copper pipes at great at carrying water, and you can wear gold safelywater, and you can wear gold safely

However others are more reactive, such as However others are more reactive, such as calcium and magnesium…calcium and magnesium…

SummarySummary

Metals differ in how reactive they are - some are very Metals differ in how reactive they are - some are very reactive, others are less soreactive, others are less so

Some Some metalsmetals react with react with waterwater, producing a , producing a metal metal hydroxidehydroxide + + hydrogenhydrogen (e.g. caclium) (e.g. caclium)

MetalMetal + + waterwater metal hydroxidemetal hydroxide + + hydrogenhydrogen