1.
Substances that are _______ will turn litmus (pH) paper reddish orange.
Correct Answer
A. Acids
Explanation
Acids are substances that have a low pH value, typically below 7. When litmus paper, which is a pH indicator, comes into contact with acids, it changes color to reddish orange. This is because acids release hydrogen ions (H+) when dissolved in water, which react with the litmus paper and cause the color change. Bases, on the other hand, have a high pH value and turn litmus paper blue or green. Neutral substances have a pH value of 7 and do not cause any color change on litmus paper.
2.
_________ tests as an acid on the pH scale.
Correct Answer
B. Lemon juice
Explanation
Lemon juice tests as an acid on the pH scale because it contains citric acid. When dissolved in water, citric acid releases hydrogen ions, which lower the pH level and make the solution acidic. This is why lemon juice tastes sour and can be used as a natural cleaning agent due to its acidic properties.
3.
Which part of an atom has a negative charge?
Correct Answer
C. Electron
Explanation
Electrons are the negatively charged particles found in the outer shells of an atom. They orbit around the nucleus, which contains protons and neutrons. Protons have a positive charge, while neutrons have no charge. Therefore, the correct answer is electron.
4.
Which part of an atom has a positive charge?
Correct Answer
A. Proton
Explanation
Protons are subatomic particles found in the nucleus of an atom. They have a positive charge, which is equal in magnitude but opposite in sign to the negative charge of electrons. Neutrons, on the other hand, are neutral particles with no charge, while electrons have a negative charge. Therefore, the correct answer is proton, as it is the part of an atom that carries a positive charge.
5.
Solutions with a pH of 7 are said to be ______________.
Correct Answer
A. Neutral
Explanation
Solutions with a pH of 7 are considered neutral because pH is a measure of the acidity or basicity of a solution. A pH of 7 indicates that the solution is neither acidic nor basic, meaning it has an equal concentration of hydrogen ions (H+) and hydroxide ions (OH-), resulting in a balanced pH level.
6.
In the water molecule, the oxygen atom tends to keep the hydrogens' electrons a little closer. This gives the oxygen end of the molecule a slightly ___________ charge.
Correct Answer
C. Negative
Explanation
In a water molecule, the oxygen atom has a higher electronegativity than the hydrogen atoms. This means that the oxygen atom attracts the shared electrons in the covalent bond more strongly, creating a partial negative charge. As a result, the oxygen end of the water molecule has a slightly negative charge.
7.
Any molecule with a positive and a negative end is said to be ____________.
Correct Answer
C. Polar
Explanation
A molecule with a positive and a negative end is called a polar molecule. This polarity is caused by an uneven distribution of electrons within the molecule, resulting in one end being slightly positive and the other end being slightly negative. Water is an example of a polar molecule, as it has a positive end (hydrogen) and a negative end (oxygen).
8.
Plants are able to bring water from their roots to all parts of the plant because of _____________ _____________.
Correct Answer
B. Capillary action
Explanation
Plants are able to bring water from their roots to all parts of the plant because of capillary action. Capillary action is the process by which water is drawn upward against gravity through narrow tubes or spaces in plants. This phenomenon occurs due to the cohesive forces between water molecules and the adhesion between water molecules and the walls of the plant's xylem vessels. As a result, water is able to move from the roots to the leaves, providing essential nutrients and hydration to all parts of the plant.
9.
In the winter, fish and other creatures are able to survive without freezing at the bottom of a lake because ___________________.
Correct Answer
C. The frozen water (ice) floats, leaving the bottom of the lake protected against extremely cold air temperatures.
Explanation
The frozen water (ice) floats, creating a layer on the surface of the lake. This layer acts as an insulating barrier, preventing the extremely cold air temperatures from reaching the bottom of the lake. As a result, fish and other creatures are able to survive without freezing at the bottom of the lake.
10.
Water molecules are attractied to molecules of other substances because of a property called ___________.
Correct Answer
B. Adhesion
Explanation
Water molecules are attracted to molecules of other substances because of a property called adhesion. Adhesion is the ability of water molecules to stick to the molecules of other substances. This occurs due to the polarity of water molecules, which allows them to form hydrogen bonds with other polar molecules. These attractive forces between water and other substances enable water to wet surfaces, climb up capillary tubes, and facilitate various biological processes such as transportation of nutrients in plants.
11.
Ice is ______________________ liquid water.
Correct Answer
B. Less dense than
Explanation
Ice is less dense than liquid water because of its unique molecular structure. When water freezes, the water molecules arrange themselves in a crystal lattice, with each molecule forming hydrogen bonds with four neighboring molecules. This arrangement causes the molecules to spread out and creates an open structure, resulting in lower density compared to liquid water. This is why ice floats on water, as substances that are less dense than the liquid they are in tend to float.
12.
Water is able to ____________ many substances because water's polar molecules are attracted to other molecules and push their way into spaces to break up the substances.
Correct Answer
C. Dissolve
Explanation
Water is able to dissolve many substances because water's polar molecules are attracted to other molecules and push their way into spaces to break up the substances. This allows water to surround and separate the molecules of a solute, causing them to disperse evenly throughout the water and form a solution.
13.
What is the only substance that can be found somewhere on Earth in all three states--solid, liquid, and gas?
Correct Answer
A. Water
Explanation
Water is the only substance that can be found in all three states - solid, liquid, and gas - on Earth. In its solid state, water exists as ice, in its liquid state, it is water, and in its gaseous state, it is water vapor. This is due to the unique properties of water, such as its high boiling and freezing points, which allow it to exist in all three states at different temperatures and pressures.
14.
This photo illustrates a property of water called ________ because you can see how the water molecules cling to each other to make a perfect sphere.
Correct Answer
B. Cohesion
Explanation
This photo illustrates the property of water called cohesion because you can see how the water molecules cling to each other to make a perfect sphere. Cohesion refers to the attraction between molecules of the same substance, in this case, water molecules sticking together. The spherical shape formed by the water droplets in the photo is a result of this cohesive force.
15.
This photo shows the damaging result of acid rain on a forest. Acid rain is a result of water's ability to ________________.
Correct Answer
B. Dissolve other substances
Explanation
Water's ability to dissolve other substances is the reason behind the damaging result of acid rain on a forest. Acid rain forms when water in the atmosphere combines with pollutants such as sulfur dioxide and nitrogen oxides, which are released from burning fossil fuels. These pollutants dissolve in the rainwater, forming acidic compounds. When acid rain falls on forests, it can leach vital nutrients from the soil, damage trees and plants, and even kill aquatic life in rivers and lakes.
16.
Which is an example of adhesion?
Correct Answer
C. Water tends to creep up the sides of a test tube or graduated cylinder.
Explanation
Adhesion refers to the attraction between different substances. In this case, water molecules are attracted to the surface of the test tube or graduated cylinder, causing them to "creep up" the sides. This is an example of adhesion because water is sticking to a surface that is different from itself.
17.
How does the pH of acid rain compare to the pH of distilled water?
Correct Answer
B. The pH of acid rain is lower than that of distilled water.
Explanation
Acid rain is formed when pollutants in the air, such as sulfur dioxide and nitrogen oxides, react with water vapor to create sulfuric acid and nitric acid. These acids lower the pH of rainwater, making it more acidic. Distilled water, on the other hand, has a neutral pH of 7. Therefore, the pH of acid rain is lower than that of distilled water.
18.
These white carnations changed color because
Correct Answer
C. Water traveled up to the flowers through capillary action
Explanation
The white carnations changed color because water traveled up to the flowers through capillary action. Capillary action is the process by which water is drawn upwards against gravity through narrow tubes or spaces, such as the stems of plants. In this case, the water carried pigments or dyes with it as it traveled up the stem, causing the white carnations to change color.