Science midterm

A single carbon atom can form a maximum of how many single covalent bonds? a. 2 b. 4 c. 6 d. 8

b. 4

Science midterm

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Because ammonia releases hydroxide ions, it is called a(n) ___________.

Base

Compare and contrast covalent and ionic bonds.

Botha are chemical bonds. Covalent bonds are formed when electrons are shared. Ionic bonds are formed when electrons are donated or accepted.

A _________increases the rate of a reaction by lowering the activation energy

Catalyst

When a mixture or substance changes color or heats up, this provides evidence that a _________ has taken place.

Chemical reaction

Magnesium and oxygen combine to form a new substance, magnesium oxide, which is a(n) ____________.

Compound

When atoms share electrons equally, they form a(n) ___________ bond.

Covalent

33. Use the graph above to respond to the following statement.Identify the three most abumndand elements found in living things.

Hydrogen,Carbon, and Oxygen

Two students carry out an investigation to determine the action of the enzyme pepsin on protein digestion in the human stomach. They know that gastric juice in the stomach contains water, pepsin, and hydrochloric acid. They decide to use small, equal-sized pieces of cooked egg white as the protein to be digested. They set up four test tubes and place equal, small amounts of egg white in each test tube. Then they fill each test tube with a different liquid to a height of 3 cm. To test tube 1 they add water, to test tube 2 they add dilute hydrochloric acid (HCl), to test tube 3 they add pepsin in water, and to test tube 4 they add pepsin and dilute hydrochloric acid. They place the four test tubes in an incubator set at 37°C (body temperature). After one day, they observe the results. They return the test tubes to the incubator and observe them again the next day. Table 6-2 is the record of the results. Table 6-2 Test tube 1. egg + water 2. egg + HCl 3. egg + pepsin 4. egg + pepsin + HCl 1 day no change no change liquid slightly cloudy, egg white solid liquid cloudy, pieces of egg smaller 2 days no change no change liquid cloudy, egg white still solid liquid very cloudy, almost no egg remains Pe34. Write a conclusion to the experiment. Base your conclusion on the experimental results shown in Table 6-2. 35. Compare and contrast covalent and ionic bonds.

Pepsin digest the protein of egg whites slightly at body temperature. In the presence of the acid HCI, the digestion of the protein was much more efficient

Positively charged particles in an atom are called _________.

Protons

Which test tube or tubes are the experimental group? Why do you say so?

Test tubes 2,3, and 4 are the experimental group because they contain substances that the experimenter believed might affect egg whites

In humans and other multicelluar organisms, which substance plays a central role as an energy source? a. carbohydrate b. fat c. protein d. water

a. carbohydrate

You are analyzing a compound in a laboratory. You find that it is made up of carbon, hydrogen, and oxygen in a ratio of two hydrogen atoms for each carbon atom. How will you classify the compound? a. carbohydrate b. lipid c. protein d. nucleic acid

a. carbohydrate

An organic compound is a compound that contains a. carbon. b. hydrogen. c. oxygen. d. sodium.

a. carbon

How does an enzyme influence a biological reaction? a. It increases the net energy difference between reactants and products. b. It decreases the activation energy necessary to initiate the chemical change. c. It increases the kinetic energy of reactants, thereby increasing their tendency to collide. d. It decreases the kinetic energy of reactants, enabling them to undergo chemical change more easily.

b. It decreases the activation energy necessary to initiate the chemical change.

Which defines an atom? a. building block of energy b. building block of matter c. charged particle d. smallest particle

b. building block of matter

Which element would need to be removed from the molecule in Figure 6-2 to make it unsaturated? Figure 6-2 a. carbon c. oxygen b. hydrogen d. phosphorus

b. hydrogen

Which is an example of a chemical reaction? a. ice melting b. iron rusting c. sugar dissolving in water d. water evaporating

b. iron rusting

Which macromolecule stores energy for an organism? a. carbohydrate b. lipid c. nucleotide. d. protein

b. lipid

A single covalent bond forms when two atoms do which of these? a. when they share one electron b. when they share two electrons c. when one gives an electron to the other d. when one gives two electrons to the other

b. when they share two electrons

A molecule of water (H2O) has which bonds? a. 1 covalent bond c. 2 covalent bonds b. 1 ionic bond d. 2 ionic bonds

c. 2 covalent bonds

Biological buffers function to achieve a pH range of ________ a. 4.5-5.5 b. 5.5-6.5 c. 6.5-7.5 d. 7.5-8.5

c. 6.5-7.5

What makes a water molecule polar? a. Water has the ability to be frozen. b. The pH of pure water varies with the temperature. c. A water molecule has a slight charge on each end. d. A water molecule is made up of three atoms.

c. A water molecule has a slight charge on each end.

Which element is found in proteins but not carbohydrates or lipids? a. C b. H c. N d. O

c. N

When added to water, how does an acid affect the pH and H+ concentration? a. Both pH and H+ decrease. b. Both pH and H+ increase. c. The pH decreases while the H+ increases. d. The pH increases while the H+ decreases.

c. The pH decreases while the H+ increases.

Which is true about enzymes? a. They act on nonspecific, randomly chosen substrates. b. After a reaction, they cannot be reused. c. They can speed up metabolic processes in the body. d. They cannot change shape.

c. They can speed up metabolic processes in the body.

One isotope of carbon differs from another in which way? a. atomic number b. number of electrons c. number of neutrons d. number of protons

c. number of neutrons

An atom of fluorine has nine electrons. Its second energy level has ____. a. two electrons c. seven electrons b. eight electrons d. nine electrons

c. seven electrons

A student set up four test tubes containing starch solution in which to perform starch digestion. Supplies included amylase (enzyme that digests starch) and an incubator. In which tube listed would starch digestion proceed most quickly? a. Tube 1: No amylase, room temperature (25°C) b. Tube 2: No amylase, body temperature (37°C) c. Tube 3: Amylase present, room temperature (25°C) d. Tube 4: Amylase present, body temperature (37°C)

d. Tube 4: Amylase present, body temperature (37°C)

The diagram below shows two amino acids. What would biochemists call the result of chaining many of these molecules together? a. a carbohydrate b. a lipid c. a nucleic acid d. a protein

d. a protein

Ions form when _________ a. an atom gains neutrons. b. an atom loses neutrons. c. one atom gives up a proton to another atom. d. one atom gives up an electron to another atom.

d. one atom gives up an electron to another atom.

Amino acids are the building blocks of which macromolecule? a. carbohydrate b. DNA c. lipid d. protein

d. protein

Which is the best example of a solution? a. blood b. milk c. paint d. seawater

d. seawater

You suspect that a chemical that you are testing in the lab is strongly acidic. What might be its pH? a. 2 b. 7 c. 11 d. 14

a. 2