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TEAS 7 Science TEAS 7 Science Practice Test 2 In the following single-replacement reac...

In the following single-replacement reaction, ______ replaces ______. Cl2+2NaI→2NaCl+I2

A. sodium, iodine

B. chlorine, iodine

C. chlorine, sodium

D. sodium, chlorine

Answer Explanation:

In this reaction, chlorine (Cl2) is an element in the reaction that replaces iodine in the compound sodium iodide (NaI). This allows chlorine to form a compound with sodium (NaCl) and leaves iodine (I2) as an element. 

Synthesis reactions involve two or more reactants (A and B) combining to form one product (AB). In the example provided, hydrogen (H2) and oxygen (O2) begin as separate elements. At the end of the reaction, the hydrogen and oxygen atoms are bonded in a molecule of water (H2O).

Decomposition reactions have only one reactant (AB) that breaks apart into two or more products (A and B). In the example above, hydrogen peroxide (H2O2) breaks apart into two smaller molecules: water (H2O) and oxygen (O2).

Single-replacement reactions involve two reactants, one compound (AB) and one element (C). In this type of reaction, one element replaces another to form a new compound (AC), leaving one element by itself (B). In the example, zinc replaces hydrogen in hydrochloric acid (HCl). As a result, zinc forms a compound with chlorine, zinc chloride (ZnCl2), and hydrogen (H2) is left by itself.

Double-replacement reactions involve two reactants, both of which are compounds made of two components (AB and CD). In the example, silver nitrate, composed of silver (Ag1+) and nitrate (NO31-) ions, reacts with sodium chloride, composed of sodium (Na1+) and chloride (Cl1-) ions. The nitrate and chloride ions switch places to produce two compounds that are different from those in the reactants.

Combustion reactions occur when fuels burn, and they involve specific reactants and products, as seen in the examples below. Some form of fuel that contains carbon and hydrogen is required. Examples of such fuels are methane, propane in a gas grill, butane in a lighter, and octane in gasoline. Notice that these fuels all react with oxygen, which is necessary for anything to burn. In all combustion reactions, carbon dioxide, water, and energy are produced. When something burns, energy is released, which can be felt as heat and seen as light.

Therefore, the Correct Answer is B.

More Questions on TEAS 7 Science

  • Q #1: What body system is the skeletal system most closely associated with when hematopoiesis happens?

    A. Urinary system

    B. Digestive system

    C. Muscular system

    D. Cardiovascular system

    Answer Explanation

    The cardiovascular system is closely associated with hematopoiesis because it includes the heart and blood vessels, which are responsible for circulating blood throughout the body. Hematopoiesis, the process of blood cell formation, primarily occurs in the bone marrow, which is part of the skeletal system. However, the cardiovascular system plays a crucial role in transporting these blood cells to various parts of the body once they are produced in the bone marrow.

    So, while the skeletal system provides the site for hematopoiesis, the cardiovascular system is responsible for distributing the blood cells, making it the most closely associated system in this context.

  • Q #2: A researcher notices a positive correlation between the height of a plant and nutrient concentration over time. Based on this observation, what conclusion does he reach?

    A. The height of a plant increases in the absence and presence of the nutrients

    B. When the amount of nutrients available to the plant decreases, its height increases.

    C. The amount of nutrients available to a plant is independent of how tall the plant gets

    D. When the amount of nutrients available to the plant increases, its height also increases.

    Answer Explanation

    Because this is a positive correlation, if the nutrient concentration increases or decreases, plant height will either increase or decrease accordingly.

    While analyzing data, scientists tend to observe cause-and-effect relationships. These relationships can be quantified using correlations. Correlations measure the amount of linear association between two variables. There are three types of correlations:

    Positive correlation: 
    As one variable increases, the other variable also increases. This is also known as a direct correlation.

    Negative correlation: 
    As one variable increases, the other decreases. The opposite is true if one variable decreases. A negative correlation is also known as an inverse correlation or an indirect correlation.

    No correlation: 
    There is no connection or relationship between two variables.

  • Q #3: Which example is part of the scientific method?

    A. A student reads about a new way to harness energy from the sun.

    B. A researcher studies the effects of car exhaust on how people breathe.

    C. A researcher analyzes how many plants respond well to a new fertilizer

    D. A student discovers how insulin plays a role in the development of diabetes

    Answer Explanation

    One step of the scientific method is to analyze information or data collected from the experiment to conclude whether the hypothesis is supported.

    Recall that these make up the scientific method, described below:

    • Problem: The question created because of an observation. Example: Does the size of a plastic object affect how fast it naturally degrades in a lake?
    • Research: Reliable information available about what is observed. Example: Learn how plastics are made and understand the properties of a lake.
    • Hypothesis: A predicted solution to the question or problem. Example: If the plastic material is small, then it will degrade faster than a large particle.
    • Experiment: A series of tests used to evaluate the hypothesis. Experiments consist of an independent variable that the researcher modifies and a dependent variable that changes due to the independent variable. They also include a control group used as a standard to make comparisons. 
      • Example: Collect plastic particles both onshore and offshore of the lake over time. Determine the size of the particles and describe the lake conditions during this time period.
    • Observe: Analyze data collected during an experiment to observe patterns. 
      • Example: Analyze the differences between the numbers of particles collected in terms of size.
    • Conclusion: State whether the hypothesis is rejected or accepted and summarize all results.
    • Communicate: Report findings so others can replicate and verify the results.

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