Substances can be classified as elements, compounds or mixtures.
Which of these is the formula for a molecule of an element? A NH3\text{NH}_3NH3 B H2O\text{H}_2\text{O}H2O C N2\text{N}_2N2 D NaCl\text{NaCl}NaCl
Which of these is a pure substance? A brass B mineral water C sodium chloride crystals D petroleum
Which method can be used to separate a mixture of ink pigments? A chromatography B fractional distillation C filtration D simple distillation
A student adds a large crystal of potassium chloride to some water in a beaker and leaves the beaker for a day.
The diagram shows the beaker immediately after adding the crystal, and after one day.
After a day, the student takes a sample from the top of the liquid and tests it to see if it contains chloride ions.
The test is positive. Describe how the student should do the test. Include the observation for a positive test in your answer.
Name the process by which potassium and chloride ions move from the crystal to the top of the liquid.
Fractional distillation can be used in a laboratory to separate ethanol from a mixture of ethanol and water.
The passage describes what happens when the apparatus is used. Use words from the box to complete the passage. You may use each word once, more than once or not at all.
beakercondenserflaskfractionating columnfunnelthermometer \begin{array}{|ccc|} \hline \text{beaker} & \text{condenser} & \text{flask} \\ \text{fractionating column} & \text{funnel} & \text{thermometer} \\ \hline \end{array} beakerfractionating columncondenserfunnelflaskthermometerThe mixture of ethanol and water is heated in the ____________ .
The vapour is cooled back into a liquid in the ____________ .
The column that helps separate the vapours of the two liquids is called the ____________ .
Which of these changes of state occurs in the flask during heating? A (s)→(g)\text{(s)} \rightarrow \text{(g)}(s)→(g) B (l)→(g)\text{(l)} \rightarrow \text{(g)}(l)→(g) C (g)→(l)\text{(g)} \rightarrow \text{(l)}(g)→(l) D (l)→(s)\text{(l)} \rightarrow \text{(s)}(l)→(s)
