Is the contamination of a river a chemical change?

To save time, you can approximate the initial mass of the solid to the nearest ±1 g. for example, if you are asked to add 14.3 g of copper, add between 13 g and 15 g. which of the following sets include two samples with an equal density? which all that apply below 15.4 g gold and 18.7 g silver 15.2 g copper and 50.0 g copper 20.2 g silver and 20.2 g copper 11.2 g gold and 14.9 g gold

In numbering carbon atoms in the parent chain of a hydrocarbon, why would you number from right to left, rather than left to right

As you watch a surfer ride a wave towards the shoreline, what is the shoreline? a) displacement reference b) reference point c) coordinate plane d) cartesian boundary