Uploaded by tom_tcf1

Mixtures worksheet 1

advertisement
SC2a.2
Name
The purity of gold
Class
Date
Table A shows information about gold. Gold is not often used in its pure form to make jewellery. A ‘fineness
scale’ is used to show how pure gold is. A number lower than 1000 on this scale means it is impure. Adding
different elements to form a mixture means that the composition of the mixture isn’t necessarily fixed. The
table below contains information about different mixtures containing gold. Use the data in the table to answer
the questions that follow the table.
A Composition and melting point of gold and gold alloys
Alloy name
* Carats
Composition by
mass
Approximate melting
temperature (°C)
Yellow gold
14 carat gold
58% gold
4–28% silver
14–28% copper
829–874
Yellow gold
18 carat gold
75% gold
10–20% silver
5–15% copper
915–963
Pure gold
24 carat gold
100% gold
1063
* A way of measuring the purity of gold is ‘carats’. Pure gold is called ‘24 carat gold’. Gold mixed with other metals has a
carat number lower than 24, depending on how much gold is included.
1
2
a
What is the percentage of gold in 18 carat gold?
b
Does 18 carat gold contain more or less gold than the same mass of 24 carat gold? Explain your
answer using information from the table.
c
Luke says you can tell that 24 carat gold is pure by looking at its melting temperature. Explain how you
can do this.
a
Ryan said that 18 carat gold is a mixture, but Jane said it is a pure substance. Who is right? Explain
your answer.
b
Explain why yellow gold melts over a range of temperatures.
c
What is the mass of gold in a 2.5 g ring made of 18 carat gold?
© Pearson Education Ltd 2016. Copying permitted for
purchasing institution only. This material is not copyright free.
3
Download