The method and the results are on the synthetic materials lab. Do the analysis yourself first, then check the answers below.
Quick answer: Synthetic materials are substances made by people through chemical reactions, usually from natural resources such as crude oil. These answers go with the grade 8 science lab on synthetic materials: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Here are the synthetic materials lab answers for grade 8 science: graph, calculations, uncertainties and conclusion. First do the lab yourself, then compare, and go back to the lesson if needed.
Model answers follow, with calculated results in bold. Small differences in your own values are normal, so check that your method and units match the model before comparing numbers.
Pieces with a density below 1.00 g/cm³ float: A and C float; B, D and E sink.
Question 4 Air bubbles
A bubble adds volume, so the water level rises too much. A larger volume gives a smaller density, so the value is too low.
Question 5 Uncertainty
Both readings can be wrong by 0.5 mL, so the volume is uncertain by ±1.0 mL. 1.0 ÷ 5.0 × 100 = 20 %.
Question 6 PET and PVC
Their densities (1.38 and 1.40) differ by only 0.02 g/cm³, which is about 1.4 %. The 20 % uncertainty is much larger, so the difference is not significant.
Question 7 Improving the method
Use larger pieces and a narrower cylinder with finer divisions, so the reading error is smaller compared with the volume. Bigger sample, finer scale.
