Question

1. mrs. lowls set up a lab for her biology students using a culture of the small crustacean daphnia, obtained from a pond that was 20°c. the students are to investigate the effect temperature has on daphnia. the students will observe the crustaceans heartbeat under the microscope, at different temperatures, and count the number of heartbeats per second.

if the experiment is designed correctly, what will the students choose for the experimental treatment? (a.1.b, a.4.c)

a. placing each of 5 identical cultures of daphnia at a different temperature
b. placing 5 cultures, each with a different type of crustacean, at a different temperature
c. placing 5 cultures, each with a different type of crustacean, at 20°c
d. placing 5 identical cultures of daphnia at 20°c

1. what is the independent variable in this experiment? (a.1.b, a.4.c)

a. number of daphnia in the cultures
b. number of heartbeats per second
c. temperature of the samples
d. type of microscope used

1. which of the following represents the correct pairing of subatomic particle and charge? (a.5.a)

a. neutrons, negative
b. neutrons, no charge
c. electrons, positive
d. protons, negative

1. when a small neutral atom becomes an ion, the number of which subatomic particle has changed? (a.5.b)

a. photons
b. electrons
c. neutrons
d. protons

1. the hydrogen atoms of a water molecule are bonded to the oxygen atom by strong _ bonds, whereas neighboring water molecules are held together by weak _ bonds. (a.5.c)

a. polar covalent; ionic
b. hydrogen; polar covalent
c. polar covalent; hydrogen
d. ionic; covalent

1. what is the main factor that determines the polarity of a bond between atoms in a molecule such as water? (a.5.i)

a. the difference in the relative attraction of electrons to each atom
b. the difference in the relative attraction of protons to each atom
c. the total number of electrons involved in the bond
d. the total number of protons and neutrons in both atoms

1. a bond that forms when electrons are equally shared between atoms is called a (n) ___ bond. (a.5.c)

a. polar covalent
b. non polar covalent
c. hydrogen
d. ionic

Explanation:

1. To investigate the effect of temperature on Daphnia's heartbeat, the experimental treatment should vary the temperature while keeping the Daphnia culture the same. Option A does this by placing 5 identical Daphnia cultures at different temperatures.
2. The independent variable is the factor that is deliberately changed in an experiment. Here, the temperature of the samples is being changed to see its effect on Daphnia's heartbeat, so temperature is the independent variable.
3. Neutrons have no charge, electrons have a negative charge, and protons have a positive charge. So the correct pairing is neutrons - no charge.
4. When a neutral atom becomes an ion, it gains or loses electrons. Protons and neutrons are in the nucleus and don't change in normal ion - formation processes, and photons are not subatomic particles involved in ion - formation.
5. In a water molecule, hydrogen atoms are bonded to the oxygen atom by polar covalent bonds due to the unequal sharing of electrons. Neighboring water molecules are held together by hydrogen bonds.
6. The polarity of a bond in a molecule like water is determined by the difference in the relative attraction of electrons to each atom (electronegativity difference).
7. A bond where electrons are equally shared between atoms is a non - polar covalent bond. Polar covalent bonds have unequal electron sharing, hydrogen bonds are intermolecular forces, and ionic bonds involve electron transfer.

Answer:

1. A. Placing each of 5 identical cultures of Daphnia at a different temperature
2. C. Temperature of the samples
3. B. Neutrons, No charge
4. B. Electrons
5. C. polar covalent; hydrogen
6. A. The difference in the relative attraction of electrons to each atom
7. b. non polar covalent