Physical sciences make up 40% of the GED Science subject test. Get yourself ready with these GED chemistry practice questions (answers at the end of the post).
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GED Chemistry Practice Questions
Questions 1-3 are based on the following information and diagrams.
Atoms are made up of three major components— protons, neutrons, and electrons. Protons are positively charged particles located in the nucleus (center) of the atom. The number of protons in an atom corresponds with the atomic number of that element on the periodic table. Also found in the nucleus are neutrons, which have a neutral charge. Orbiting outside the nucleus are electrons, which have a negative charge. An atom has the same number of protons and electrons, so the overall charge of the atom balances out to be neutral.
Model of an atom:
Image by köbes.
1. Identify each colored circle in the atomic model as either a proton, neutron, or electron.
2. The white circles have a _______ charge.
3. The atomic model shows an atom of which element?
4. Chemical equations should be balanced, meaning there are the same number of atoms of each type of element on both sides of the reaction. Fill in the coefficients needed to balance the chemical equation below.
C3H8 + 5O2 → __ CO2 + __ H2O
Questions 5-10 are based on the following information and diagram.
Most liquids are either acids or bases. When mixed with water, some compounds release hydrogen ions (H+) and some release hydroxide ions (OH–). Substances that increase the H+ concentration are called acids and those that increase the OH– concentration are called bases.
Whether a substance is acidic or basic (and to what degree) is measured on something called the pH scale. The pH scale goes from 0-14. Acids are less than 7 on the pH scale; bases are greater than 7. Substances that have a pH of exactly 7 are neutral. The pH scale is based on H+ levels.
There is also a pOH scale, which is based on OH– levels. It, too, ranges from 0-14, but in the opposite direction as pH. On the pOH scale, a value less than 7 indicates a base, while a number greater than 7 indicates an acid. Again, 7 is neutral. The pH and pOH for a given substance always add up to 14.
When a strong acid (pH 0-4) and a strong base (pH 10-14) react with one another, they neutralize, forming products of water (H2O) and a salt.
Acidity can be measured using a litmus test. Acids turn litmus paper red, while bases turn them blue.
Image by PatriciaR.
5. A solution of NaOH has a pH of 11. The substance is
6. The pOH of the same NaOH solution would be ____.
7. This NaOH solution results in an increase in the concentration of which type of ions?
8. A litmus test on the NaOH solution would show which color?
9. If the NaOH solution reacted with a ___________ such as HCl, it would form water and salt.
A. weak acid
B. weak base
C. strong acid
D. strong base
10. Based on the scenario in question #8, complete the chemical equation below:
NaOH + HCL → ______ + _______
Questions 11-14 are based on the following diagrams. The first shows the phases changes that matter can undergo, the second shows the heating curve of water, and the third shows how the Celsius and Fahrenheit temperature scales compare.
|A change from a...||... to a...||is called...|
Image by the Community College Consortium for Bioscience Credentials.
Image by TheVovaNik.
11. At which temperature is water the least dense?
12. Freezing happens at a temperature of _____°C.
13. At which temperatures does water exist as a solid? (Select all that apply.)
14. Which is NOT a phase change that occurs at a temperature of 100°C?
1. Blue: electrons; Red: protons; White: neutrons
The blue ones must be electrons because they are located outside the nucleus (center) of the atom. The red circles must be the protons because there are three red circles and four white circles, and the number of protons and electrons must be equal. Since you already know that there are three electrons, there must also be three protons. By process of elimination, the white circles must be the neutrons.
As established in question 1, the white circles are the neutrons. As the name implies, neutrons have a neutral charge, which means they are neither positive nor negative.
The text tells you that the number of protons in an atom corresponds with the atomic number of that element on the periodic table. The atomic model shows that this atom has three protons. Look this atomic number up on the periodic table and you will find that the corresponding element is lithium.
4. 3; 4
On the left side, there are:
3 C (carbon)
8 H (hydrogen)
10 O (oxygen), since there are 5 molecules of 2 oxygen atoms each: 5(2)=10
You need the right side to match this. You know you need 3 carbons, so you can start with putting a 3 in front of CO2. This gives you 3(2) = 6 oxygen atoms so far, so you need 4 more to balance the equation. Place that 4 in front of the H2O. Double check that this also makes your hydrogen atoms match. On the left side, there are 8 H. On the right, you now have 4H2O, so that’s 4 molecules with 2 hydrogen atoms each, for a total of 4(2) = 8 H. These match, so the equation is balanced.
A pH above 7 indicates a base.
pH and pOH must add up to 14. If the pH is 11, the pOH must be 3.
Bases increase the OH– concentration.
Bases show up as blue on litmus tests.
The text tells you that a strong acid and a strong base react to form a salt and water. Since you’ve already established that NaOH is a base, you’d need a strong acid to create this reaction. Hydrogen chloride (HCl, also known as hydrochloric acid when in an aqueous solution) is a strong acid.
10. H2O; NaCl (you can also have them reversed; the order does not matter)
You already know from the text and the previous question that the products must be water and a salt. You may not know the chemical formula for a salt, but you should know the formula for water (H2O) and you can use that to figure out what must be in the salt. Remember that the two sides of a chemical equation must be balanced. On the left side of the arrow (the information already given to you), you have:
NaOH + HCl
That means you have:
When you balance this equation, you’ll need those same numbers on the other side. Go ahead and add in water since you know that has to be one of the products.
NaOH + HCL → H2O + _______
Now on the right side, you have:
To make it the same as the left, you need 1 Na and 1 Cl. Since you know there’s only one product left, it has to be NaCl, which happens to be sodium chloride (salt).
NaOH + HCL → H2O + HCl
Water is least dense in a gaseous state, which occurs above a temperature of 100°C.
Water changes from a liquid to a solid (freezing) at the same point that it can change from a solid to a liquid (melting), which is at 0°C.
13. A, B, C
Note that the temperatures given are in Fahrenheit, so you need to convert from Celsius to Fahrenheit using the thermometer diagram if you’re going by the heating curve of water graph. Water freezes at a temperature of 0°C, which is equal to 32°F. Water will exist as a solid at any temperature below this point, which means that water will be solid at -10°F (A), 5°F (B), and 30°F (C).
Vaporization and boiling are the same thing- a change from liquid to gas. Condensation is the reverse- a change from a gas to a liquid. Both occur at a temperature of 100°C. Freezing, however, occurs not at 100°C but at 0°C. Freezing is the change from a liquid to a solid.