investigate the malleability of quenched and annealed metals.
Three similar sewing needles.
Two pairs of pliers.
A heat source, such as a gas flame or hotplate.
A cup of iced water.
Wear safety glasses during this experiment.
1. Using the
pliers hold the first needle and flex it slightly to get the feel of its
2. Heat the
centre if the second needle in the hottest part of a flame, so that it is red
hot, and then drop it in the iced water. Take it out and try the elasticity.
Does it spring back when flexed the same amount as before?
the unheated needle a similar amount. Is there any difference in the
brittleness between the heated and unheated needles?
both needles. Compare the hardness at the breaks. Record your observations
3. Take the
third unheated needle and heat it until it is red hot. This time remove it
gradually from the flame so that the centre part cools slowly, over about two
minutes. When it is cool try bending it. Does it spring back, bend permanently
Take this last needle again, heat it red hot, and then quench
it in cold water. Then heat it again less strongly until almost red hot, and
then cool gradually over two minutes.
Flex the needle. Is there any difference in the brittleness
between this needle and the other two needles?
Break the needle. Compare the hardness at the break. Record
three processes used in this experiment .
the rate of cooling affects the brittleness and size of the crystals formed.
terms of bonding why quenching metals are harder than unquenched metals?
it is difficult to straighten a bent metal coat hanger
In 2 mole
mole of N atoms are there?
mole of O atoms are there?
the number of O atoms.
the molar mass of the following compounds.
the molar mass of methane, CH4
answer to (a) to work out:
The mass of
2 mol CH4
The mass of
H atoms in 2 mol CH4
the molar mass of water, H2O
answer to (a) to work out the number of mol in:
state how you input numbers in standard form on your calculator. For example,
how would you input the number 5×10^12
b ) Use your calculator to work out
the number of mol contained in:
3.10×10^23 molecules of octane.
2.408×10^24 molecules of nitrogen.
the percentage composition of all the elements in Ni2(SO4)3
Show your working.
7. In 3 mole of C3H8 molecules:
moles of C atoms are there?
mole of H atoms are there?
the number of C atoms.
the number of H atoms.
8. a) Which
contains the greater number of molecules:
1 mole C2H6 or 2 mole I2?
b) Which contains the greater
number of atoms:
2 mole MgCl2 or 2 mole O2?
9. Work out
the mass of 2.6mole of Mg3(PO4)2
10. a) How many
mole are contained in 4.2×10^25 molecules of methanol, CH3OH?
b) Work out the mass of the
the percentage of water in the compound ZnSO4 . 4H20
a) What are
some of the limitations of the “metallic lattice” model for metals?
b) How does the “ball bearing” model explain why some
metals bend more easily than others do?