7th Grade - Chapter 3 Practice Test

This Practice test is solely to aid students. These are not the actual test questions but simialr questions that will help the students practice.

Inside the Atom
I. Testing Concepts
Directions: For each of the following, complete the sentence.
1. ______ contain(s) only one kind of atom.
2. A(n) ______ is the basic unit of matter.
3. Particles in an atom's nucleus that do not have an electric charge are called ______.
4. The atomic mass of an atom consists of the mass of the ______.
5. In an atom, the electrons can be found in the ______.
6. J. J. Thomson used the fact that ______ charges attract each other in his cathode-ray tube experiment.
7. The mass number of an isotope is the number of ______.
8. Isotopes are atoms of the same element that have a different number of ______.
9. To find the number of neutrons in an isotope, subtract the______.
a. atomic number from the mass numberb. mass number from the atomic numberc. number of isotopes from the mass numberd. number of protons from the number of electrons
_______ 10. The most stable isotope of an atom with 12 protons probably has ______ neutrons.
11. The strong nuclear force holds the ______ together.
12. Radioactive decay is the release of ______.
13. A(n) ______ particle consists of two protons and two neutrons.
14. The changing of one element into another in radioactive decay is called ______.
15. Radioactive decay can be affected by ______.
16. A radioactive isotope has a half-life of 100 years. A sample of 40 g of the isotope will have a mass of ______ g in 200 years.
17. Tracer elements can be used without danger to people because they have ______ halflives.
Directions: Identify each statement as true or false. Rewrite false statements to make them correct.
18. A proton is a positively charged particle present in the nucleus of all atoms.
19. The mass of a proton is much greater than the mass of a neutron.
20. Atoms of the same element can have a different number of neutrons.
21. Dalton believed that the atom was a hard sphere that was the same throughout.
22. J. J. Thomson did experiments that showed that atoms cannot be divided into smaller particles.
23. Rutherford's experiment showed that alpha particles could pass through foil because most of an atom is neutrally charged.
24. The strong nuclear force can hold the protons of an atom together only if the protons are far apart.
25. Once a living organism dies, the amount of carbon-14 cannot be replaced.
II. Understanding Concepts
Skill: Outlining
Directions: Answer the following questions on the lines provided.
In an outline, the subtopics are neutron, proton, and electron. What is the main topic?
In an outline, the subtopics are fossil dating, cancer detection, and circulation problems. What is the main topic?
III. Applying Concepts
Directions: Do the following calculation. Show your work in the space provided.
An atom has a mass number of 53 and an atomic number of 26. How many neutrons does it have? Include a formula that explains your calculation.
The isotopes of carbon (carbon-12, carbon-13, and carbon-14) have different mass numbers. Each isotope has six protons. Explain how you can determine the number of neutrons in each isotope.
A certain element has a half-life of 20 years. A scientist starts with 100 g of the element.
How many grams remain after 20 years?
How many grams remain after 40 years?
How many half-lives are there in a 100-year span? How many grams of the sample would remain at the end of the 100 years?
IV. Writing Skills
Directions: Answer the following question in complete sentences.
How is americium-241 used in smoke detectors?