AlkenesIB MYP Chemistry: Mind map

Exam questions on Alkenes

1. A student compares two colourless gases, ethane, C₂H₆, and ethene, C₂H₄. Both gases burn, but they behave differently when she bubbles each through bromine water.
   Explain why ethene is described as an unsaturated hydrocarbon.2 marks
2. A technician has two unlabelled colourless liquids. One is pentane, an alkane, and the other is pentene, an alkene. She adds 2 cm³ of orange-brown bromine water to 2 cm³ of each liquid in separate test tubes and shakes each tube.
   Describe what the technician sees in each test tube and how she can tell which liquid is pentene.2 marks
3. A student has four colourless liquids labelled P, Q, R and S. Each is either an alkane or an alkene. She adds 2 cm³ of bromine water to 2 cm³ of each liquid in a test tube, shakes it and records the colour of the mixture after 1 minute. P and R stay orange-brown. Q and S become colourless.
   Identify the independent variable, the dependent variable and one control variable in the student's investigation.3 marks