HWrkSht 1_14
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This Homework requires you to complete a graph on the GRAPH PAPER in your jotter. Use only a half page of graph paper for each graph. You should complete the graph on the graph sheet opposite the written answers.
1. The apparatus shown below was used to study the effect of different temperatures on the activity of the enzyme catalase.
The catalase was added and reacted with the hydrogen peroxide to release oxygen.
The increase in oxygen compared to the starting value was recorded as a percentage.
This was carried out at five different temperatures and the results are shown below.
a) Use the results to draw a line graph.
b) At which temperature was the catalase most active?
c) Why was it important that the catalase and the hydrogen peroxide were both at the required temperature before the catalase was added?
d) Explain why there was no oxygen released when the experiments were repeated with different enzymes.
e) Calculate the simple whole number ratio of percentage increase in oxygen at 34 °C, 40 °C and 50 °C. 34 °C ______: 40 °C ______ : 50 °C _______
(Show your working in your jotter)
2. The following apparatus was used to investigate the effectiveness of washing powders. Identical pieces of stained cloth were washed using different washing powders. The cloths were dried and the degree of stain removal was measured by recording light reflected from the cloth with a light meter. The meter was set to read 100% when the cloth was perfectly clean. Any stain left on the cloth reduced the intensity of light recorded.
Various precautions were taken to ensure that the experimental procedure was valid.
a) From the following list, identify the point(s) which contributed to ensuring the experiment was valid.
i) The procedure used gave appropriate information about the effectiveness of washing powders.
ii) All significant variables were controlled and were identical except the one being investigated.
iii) Several results were collected and used to calculate an average.
b) Explain why it was necessary to carry out the investigation in a light-proof box.
The results obtained using two different washing powders at various temperatures are shown below.
c) At which temperature was there the greatest difference between the effectiveness of the two washing powders?
d) Each one degree Celsius reduction in the washing temperature saves 2p in the cost of electricity used to heat the water for each wash.
Calculate the annual saving in the electricity costs to achieve 100% stain removal with biological washing powder compared to a non-biological one, for a household which does one wash per week
e) What type of biological substance gives biological washing powders their properties?
f) Explain why the effectiveness of the biological washing powder decreases between 40°C and 45°C.
