Question

part 1

Does a chemical or physical change force the bullet out of a gun? Would the smoke coming out of the end of the gun most likely a homogeneous or heterogeneous mixture? Explain your answers.  

Part 2

Scientific facts are measurements. They are not changeable, nor are they subject to interpretation. However, with any measurement, in science, there is a certain amount of uncertainty. This uncertainty is made up in two basic ideas: accuracy and precision.

In the real world, these terms have similar meanings. But in science, these terms are very different:

Accuracy is how close or far a measurement is from the actual value.
Precision is how well we know the value of the measurement; dependent on significant figures and reproducibility.

For example, we all generally know a few digits of the mathematical constant pi (3.141592657...). If we are given four different measurements of this mathematical constant, we can make a statement about their relative accuracy and precision:

• Measurement A: 3.1415
• Measurement B: 3.14
• Measurement C: 3.1105
• Measurement D: 3.12

Measurements A and B are equally accurate since they both correspond to a correctly rounded version of the true value. However, the first value is more precise because it contains more significant figures.

Measurement C is less accurate than Measurement A since it is not as close to the actual value. But, it is equally as precise as Measurement A.

Part I: Measurement D is more accurate than Measurement C, but Measurement C is more precise than Measurement D. (not graded for correctness)

1. Which measurement is better?
2. Why do you think it is?

Part II: (Graded for correctness)

Which of the following measurements contains 3 significant figures? If a number does not contain 3 significant figures, alter the number and report its value so it will contain exactly 3 significant figures:

1. 3000 meters

2. .0501 cm

3. 212.0 ml

4. .00026 cm

Answer 1

Part 1

Physical changes are those changes in which form of the substance changes but not chemically i.e. they can be reversed to their original form whereas in chemical change new substance formation takes place and it is irreversible.

Here both physical and chemical changes are responsible for forcing the bullet out of the gun as bullet coming out of the gun is physical change and burning of the gun powder while bullet is fired is chemical change. Also the smoke coming out of the gun is heterogeneous mixture as the smoke contains different separable substances. Therefore it comes into the category of heterogeneous substance.

#as per HomeworkLib guidelines I am supposed to answer only first question so plz post them separately.