Answer:
In order to measure the amount of solution added in or drained out, the burette must be observed at eye level straight to the bottom of the meniscus. The liquid in the burette should be completely free of bubbles to ensure accurate measurements.
Answer:
C) Pressure will compress a gas, reducing its volume and giving it a greater density and concentration of particles.
Explanation:
At constant temperature, pressure and volume are inversely related.
P V = constant

As the pressure increases, the gas compresses, the particles come closer reducing the volume of gas.
As we know, with decrease in volume, density increases.


Thus, the pressure of a gas is directly related to concentration of particles. Increase in pressure causes increase in concentration of the particles.
The independent variable would be the cleaning products.
The independent variable is the variable that you can manipulate. The change in the independent variable is not affected by other variables. So in this case, the independent variable would be the cleaning product because you will be changing it.