Question

part i - multiple choice (20 points)
circle the best answer for each question.

1. which of the following best describes a negative feedback system?

a) it amplifies a change
b) it decreases the effect of a change
c) it speeds up metabolism
d) it involves positive reinforcement

1. which of these has the lowest metabolic rate 4 hours after eating?

a) carbohydrates
b) proteins
c) fats
d) sugars

1. what is the chemical formula for water?

a) co₂
b) h₂o
c) ch₄
d) o₂

1. which element has 6 protons?

a) oxygen
b) nitrogen
c) carbon
d) helium

1. why is chlorine commonly used as a cleaning substance?

a) it adds nutrients to water
b) it reacts with bacteria and destroys them
c) it is nonreactive
d) it increases oxygen levels

1. if an object floats in water, it is:

a) more dense than water
b) less dense than water
c) the same density as water
d) denser than metal

1. which unit measures density?

a) grams
b) liters

Explanation:

1. Negative feedback systems work to counteract changes, so they decrease the effect of a change.
2. Fats have a lower metabolic rate compared to carbohydrates, proteins, and sugars (which are a type of carbohydrate) when digested.
3. The chemical formula for water is \(H_2O\). \(CO_2\) is carbon dioxide, \(CH_4\) is methane, and \(O_2\) is oxygen gas.
4. The number of protons is equal to the atomic number. Carbon has an atomic number of 6.
5. Chlorine is used as a cleaning substance because it reacts with bacteria and destroys them.
6. An object floats in water if it is less dense than water. If it were more dense, it would sink; if the same density, it would be neutrally buoyant (suspend in water).
7. Density is mass per unit volume. Grams is a unit of mass, liters is a unit of volume. The unit for density is grams per liter (or other combinations of mass and volume units). But among the given options, since the question is likely testing basic knowledge and grams and liters are presented, and density is mass/volume, grams (mass) and liters (volume - though not the full unit for density, but in a simple multiple - choice context where the other options are incorrect).

Answer:

1. B. It decreases the effect of a change
2. C. Fats
3. B. \(H_2O\)
4. C. Carbon
5. B. It reacts with bacteria and destroys them
6. B. Less dense than water
7. A. grams (Note: Technically, density is mass/volume. But if we consider the options given and the fact that grams is a part of the density unit (e.g., g/mL where mL is a volume unit), and liters (B) is only a volume unit. In a simple multiple - choice where we have to pick from the given options, grams is related to density as it is a mass unit which is in the numerator of the density formula)