What steps do scientists need to follow to make sure that a scientific investigation is replicable

Which of the following is an example of physical change not a chemical change? a) a log gives off heat and light as it burns. b) a tree stores energy from the sun in its fruit. c) a penny lost in the grass slowly changes color. d) a water pipe freezes and cracks on a cold night.

How many moles of lead are in 1.50 x 10^12 atoms of lead? could you explain the answer as well and not just give it to me i am refreshing for finals and i need to know how to do it

Achemical equilibrium between gaseous reactants and products is shown. n2(g) + 3h2(g) ⇌ 2nh3(g) how will the reaction be affected if the pressure on the system is increased? it will shift toward the reactant side as there is lower pressure on the reactant side. it will shift toward the product side as there is higher pressure on the product side. it will shift toward the reactant side as there are a greater number of moles of gas on the reactant side. it will shift toward the product side as there are a fewer number of moles of gas on the product side.