HELP
1Look at the three diagrams.
aiWhich substance is a mixture?
iiExplain why it is a mixture.
biOne diagram represents solid iron. Which one?
iiExplain why you chose your answer.
iiiWhy is this substance an element?
2Copy the table and write the substances into the correct column.
Element / Molecule / Mixture© Harcourt Education Ltd 2004 Catalyst 2
This worksheet may have been altered from the original on the CD-ROM.
CORE
3
aWhich substance is a mixture of molecules?
bWhich pure substance contains molecules?
cWhich substance might be helium?
diWhich substance might be mercury?
iiExplain your choice.
4Kevin found a piece of rock. He melted it and passed electricity through it. A gas was given off and a shiny silver solid appeared as well. Kevin could not break down the gas into a simpler substance. He found that the silver solid would burn very well. It made a brilliant flame and became a powdery white solid containing black flakes.
aThe substances could be an element, a mixture or a molecule.
Explain which description best fits each underlined substance by copying and completing the table.
Piece of rock
Gas
Silver solid
Powdery white solid with black flakes
bDescribe two important features of the atoms in the shiny silver solid.
© Harcourt Education Ltd 2004 Catalyst 2
This worksheet may have been altered from the original on the CD-ROM.
EXTENSION
5In the Middle Ages, alchemists tried to make gold. Often, kings and princes employed them. They were trying to find out how to create wealth. One idea they had was that gold could be made from yellow substances.
One recipe suggested that boiling cow’s urine might make gold. It did not!But another material called phosphorus was obtained from urine.
In the recipe, a vat of urine was boiled until it had reduced to one quarter of its original volume. The liquid was cloudy so it was filtered to remove the undissolved solids and boiled again, leaving a solid in the bottom. They could not break down this solid into anything simpler. When dry, some bits of the solid would burn with a blue flame. During burning, the bits of phosphorus reacted with oxygen.Oxygen has particles made from two oxygen atoms joined together.
In China, a group called the Taoists tried to develop an immortality pill to help them live forever. They refined cinnabar, a mineral containing mercury sulphide.Unfortunately, mercury is very toxic and their immortality pills killed many people, including several Chinese emperors!
aWhy might the alchemists have thought that gold could be made from yellow substances?
bWhat is the evidence that phosphorus is an element?
cWhat is the evidence that oxygen is an element?
dExplain how the paragraph above shows that cinnabar is not a pure substance.
eWhich two elements are found in the pure substance obtained from cinnabar?
fExplain how the information above shows that urine is a mixture.
6When mercury sulphide is heated in air it becomes mercury oxide. A gas called sulphur dioxide is given off. The mercury oxide then goes on to break down into mercury metal and oxygen gas.
aThis information contains the names of three elements. What are they?
bOne of the elements is also a molecule. Which one?
cThree pure substances, that are not elements, are also named. Write them down.
dWhere did the sulphur that was in the sulphur dioxide, come from?
eWhere did the oxygen, that reacted with the sulphur, come from?
© Harcourt Education Ltd 2004 Catalyst 2
This worksheet may have been altered from the original on the CD-ROM.