Answer:
Make an observation.
Ask a question.
Form a hypothesis, or testable explanation.
Make a prediction based on the hypothesis.
Test the prediction.
Iterate: use the results to make new hypotheses or predictions.
Explanation:
Answer: 72 grams of
are needed to completely burn 19.7 g 
Explanation:
According to avogadro's law, 1 mole of every substance weighs equal to molecular mass and contains avogadro's number
of particles.
To calculate the number of moles, we use the equation:

Putting in the values we get:


According to stoichiometry:
1 mole of
requires 5 moles of oxygen
0.45 moles of
require=
moles of oxygen
Mass of 
72 grams of
are needed to completely burn 19.7 g 
Answer:
Destructive interference will occur, causing the new wave to have less energy than Wave A or Wave B.
Explanation:
Destructive interference has lesser intensity.
THE DEFINITION OF PHYSICAL CHANGE: Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds. so the answer is that the form of the sugar is changing in water but if you boiled the water till its all evaporated all that will be left is the sugar
Answer:
The amount of space an object occupies.
Explanation: