ati teas 7 science

Correct Answer: A

Rationale: The correct answer is A: Atom. An atom is the smallest unit of an element that retains its chemical properties. Atoms are composed of protons, neutrons, and electrons. Molecules (B) are made up of two or more atoms bonded together. Compounds (C) are substances composed of two or more different elements chemically bonded. Mixtures (D) are combinations of two or more substances that are physically mixed but not chemically bonded. Therefore, in this context, the correct answer is atom as it specifically refers to the smallest amount of an element that can exist independently with its unique chemical properties.

Correct Answer: B

Rationale: The correct answer is B: Alveoli. Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide occurs during respiration. Oxygen from the air we breathe diffuses into the bloodstream, while carbon dioxide from the blood is released into the alveoli to be exhaled. The trachea (A) is a tube that carries air to and from the lungs, the bronchi (C) are branches of the trachea, and the diaphragm (D) is a muscle that helps with breathing but is not directly involved in gas exchange. Therefore, the alveoli are responsible for gas exchange in the respiratory system.

Correct Answer: B

Rationale: Platelets are responsible for blood clotting, which is crucial for preventing excessive bleeding when a blood vessel is injured. They adhere to the site of injury and form a plug to stop bleeding. This function is essential for maintaining hemostasis in the body. Platelets do not carry oxygen like red blood cells (Choice A), fight infection like white blood cells (Choice C), or transport nutrients like plasma (Choice D).

Correct Answer: D

Rationale: The correct answer is D, the independent variable. This is the variable that is intentionally changed or manipulated by the researcher in a scientific investigation to observe its effect on the dependent variable. By varying the independent variable, the researcher can determine if changes in this variable cause changes in the dependent variable. The control (B) is used as a baseline for comparison, the hypothesis (C) is a proposed explanation, and the dependent variable (A) is the variable being measured as a result of changes in the independent variable.

Correct Answer: D

Rationale: The correct answer is D because water's unique polarity allows it to dissolve a wide range of substances. Water's polar covalent bonds enable it to form hydrogen bonds with other molecules, facilitating dissolution. Water's ability to dissolve various substances is crucial for biological processes such as nutrient absorption and waste removal. Choice A is incorrect because water is neutral in terms of its pH, not inherently having a neutral pH. Choice B is incorrect because water actually has a high specific heat capacity, which is why it can absorb and release large amounts of heat without significant temperature changes. Choice C is incorrect because while water does have polar covalent bonds, this property alone does not fully characterize water as much as its dissolving capabilities do.