Week 1 HSA Review Session

Scientific Method & Inorganic/Organic Molecules

Experimentation

Scientific MethodScenario: For your science fair experiment, you want to determine how the amount of sunlight affects the size of tomato plants. You believe that the more sunlight the plants receive, the more they will increase in size. To perform your experiment, you keep one set of tomato plants under a light for 24 hours a day, another set of plants under a light for 12 hours a day, and a third set of plants without any sunlight, and a fourth set of plants outside where the amount of light changes daily.

Definition Using Scenario

Hypothesis

Independent Variable

Dependent Variable

Control Group

Experimental Group

Bias

GraphingCreate a proper graph based on the following data:

A student performed an experiment to determine the relationship between air temperature and growth in plants. She divided 36 seedlings into six groups and grew each group at a different temperature. She recorded the average height of the plants in each group after a four-week period. Her results are shown below.

Temperature (°C): Average Height (cm)

6 15

12 20

18 36

24 52

30 20

36 16

Question 1Use the information and the chart below to answer the following items.Several students are conducting an experiment to test the effect of exercise on heart rate. Students do 20 sit-ups in one minute of exercise. The data chart below shows the heart rate at one-minute intervals for each student.

1. The students decide to ignore any results that were too far above or below their prediction. They repeat these trials until a value closer to their prediction is obtained. The students’ decision to ignore data and repeat trials affects the experiment by

A.introducing biasB. decreasing controlsC. increasing accuracyD. eliminating variables

Question 2Use the information and the chart below to answer the following items.

Several students are conducting an experiment to test the effect of exercise on heart rate. Students do 20 sit-ups in one minute of exercise. The data chart below shows the heart rate at one-minute intervals for each student.

2. Which of these is the dependent variable?

A.time

B. heart rate

C. type of exercise

D. number of sit-ups

Question 3Use the information below to answer the following item.Methyl mercury is a toxic substance that can harm the nervous system. Some fish are contaminated

with high levels of methyl mercury. In many places, these fish are an important food source. Experiments are being conducted to determine how many meals of contaminated fish can be safely consumed. The table below shows the concentration of methyl mercury in the fish and the number of meals that can be safely consumed per month.

The data collected during this experiment are summarized in the graph below.

The graph has been constructed incorrectly. Which of these needs to be corrected in order to improve the graph?

A.The axes are labeled with inappropriate intervals.B. The dependent and independent variables are on wrong axes.C. The title is inconsistent with the investigation.D. One or both axes are missing units.

Question 4Students tested two cleansers for their effectiveness against bacteria. In their

experiment, each cleanser was used on two different household surfaces. The students took samples from each surface before and after using each cleanser. Then they transferred each sample to a culture medium. The students counted the number of bacterial colonies that grew on each culture medium. The results of their test are shown in the table below.

4. Which of these would be the best control for their experiment?A.Use only Cleanser 1 on both sinks and counters.B. Use Cleanser 1 on the sinks and Cleanser 2 on the counters.C. Test the number of bacteria on the counters and sinks after scrubbing without using

cleansers.D. Test the number of bacteria on the counters and sinks without scrubbing with

cleansers.

Water

Properties of WaterUniversal Solvent =

Less Dense as a Solid =

Polar (Polarity) =

Cohesion & Adhesion =

Surface Tension =

Is able to dissolve most chemicals. Water is a universal solvent because

it dissolves more substances than any other solvent.

When water is a solid (ice) it floats on liquid

water.An uneven distribution of charge.

One area of the molecule is positive and the other is negative.

Cohesion – attraction of LIKE molecules to each other.

Adhesion - attraction of UNLIKE molecules to each other.

The surface film (“skin”) on the top of a liquid caused by

molecular cohesion.

Inorganic molecules =

pH =

Non living; not made of carbon.

Relative concentrations of hydronium ions (H+) and hydroxide ions (OH-) in a

solution.

Question 5Use the information and the drawing below to answer the following item.

The pitcher plant is a carnivorous plant that consumes various small organisms such as spiders and frogs. The pitcher plant is often found in areas with soil that is very acidic and contains few nutrients. The pitcher plant consumes organisms that help supply the plant with nutrients that are not in the soil. A diagram of the pitcher plant is shown below.

In which soil pH range are pitcher plants most likely found?A.4.5–5.5B. 7–8C. 10.5–11.5D. 13–14

Question 6

Water dissolves many substances. This occurs because water has

a. surface tensionb. polarityc. specific heatd. cohesion

Question 7

When the cells of most organisms freeze, they burst. Which property of water causes this to occur?

a. Water is a universal solvent.b. Water changes temperature rapidly.c. Water is less dense as a solid than as a liquid.d. Water is a nonpolar molecule.

Macromolecules

Organic molecules = Macromolecule

Building Blocks

Function

Examples

Carbohydrate Lipids

Monosaccharide Fatty Acid

EnergyPlant cell wallstructure

Long term energy storageCell membrane component

SugarGlucoseStarch- polysaccharide cellulose

WaxFatPhospholipid Oil

Macromolecule

Building Blocks

Function

Examples

Protein Nucleic Acid

Amino Acid Nucleotide(A,C,G,T,)

Structure of hair, nails, skin & muscles

Catalysts

Store genetic information

MeatEnzymes

DNARNA

Question 8

Which statement describes the major role of lipids within a cell?

a. They cause DNA to replicate.b. They move RNA in the cytoplasm.c. They catalyze chemical reactions in the cell

cytoplasm.d. They are the main structural components of

membranes.

Question 9

A dog gets many nutrients from its food including amino acids. Which of these can be built directly using the amino acids?

a. proteinsb. carbohydratesc. lipidsd. minerals

Question 10

Which of these are the repeating units that form a DNA molecule?

a. fatty acidsb. nucleotidesc. amino acidsd. chromosomes

Question 11

Most carbohydrates in the human body are

a. used as building blocks for proteinsb. used as catalysts for reactions in cellsc. consumed as a source of energyd. not easily absorbed into the bloodstream

Question 12

Glucose is a building block of carbohydrates. Which of these best describes glucose?

a. nucleotideb. proteinc. monosaccharided. lipid

Question 13

The characteristics listed below can be used to describe some molecules.1) inorganic2) supplies energy and fiber3) component of plant cell walls4) part of DNA5) made of nucleotides

Which of these sets of characteristics describes a carbohydrate?

a. 1–3–5b. 2–3–4c. 2–4–5d. 1–3–4