TAKS Science Exit Exam Review Objective One:

The Nature of Science

What is Science?• Science involves asking questions about the

natural world (the world we see around us) and finding answers to those questions

• Specifically, scientists use the Scientific Method to try and answer questions in a fact-based, methodical way

• Scientists use Experiments, Research, Building a Models, etc., to try and find an answer to their questions

Safe/Ethical Practices• Never work alone in a lab• Never eat, drink, or apply makeup in a lab• Know where safety equipment in located in lab• Never mix chemicals unless directed by your teacher• Never work on a experiment not assigned by your teacher• Report any accidents, hazards, or spills to your teacher right away• Always handle chemicals with care—do not return to original container• Never taste, touch, smell, or substance in the lab—if you are told to do so,

waft fumes toward you with your hand• Tie back long hair, roll up loose sleeve—put on any safety equipment given

by your teacher, including safety goggles and gloves• Always wear an apron or lab coat—never wear shorts or sandals in the lab• Never pour chemicals down the drain without checking with your teacher—

dispose of chemicals and contaminated materials in appropriate containers• Handles animals as directed by your teacher—do not conduct an

investigation of animals unless told to do so by your teacher• Never remove an animal from the lab unless told to do so by teacher• Never capture an animal from the wild or release to the wild• Animals must be properly cared for—they should be given appropriate food,

water, housing, space, lighting and temperature

Lab Equipment• Safe goggles• Beakers• Test tubes• Tongs• Pipet• Forceps• Petri Dish• Microscope

Bad Question: Which brand of toothpaste tastes best?(opinion-based)

Good Question: How do factors such as temperature and surface area affect the speed of chemical change in effervescent antacid tablets dissolved in water.(fact-based)

What question to ask?

The Scientific Method

Hypothesis: Educated guess about what we think will happen in our experiment

• Problem/Question: How long does it take antacid tablets to dissolve in water and does temperature and surface area effect that chemical change?

• Research/Observation: Other substances like sugar dissolve faster in hot water vs. cold water. Sugar also dissolves faster in smaller pieces vs. larger pieces.

• Hypothesis: We hypothesize that the rate of chemical change (time it takes to dissolve) of the reactant (the antacid tablets) will increase as the temperature and surface area increases.

• Experiment: We will put different-size tablets in different temperature water and record the speed of chemical reaction (time it takes to dissolve.)

• Analysis/Conclusion: We will analyze our results to see if we can confirm or if we fail to confirm our hypothesis.

Gather the tools and equipment needed to conduct the experiment and measure the results

Controlling Variables• Variable: anything in a experiment that can change• You want to keep variables the same except the

ones you are testing• EX: We will use only one tablet per trial and using

the same amount of water per trial• Independent Variable: The things we change in the

experiment (EX: size of tablet and temperature of water.) Measurements must be precise.

• Control: normal conditions we can compare our results to (Trial 2)

Testing and Results: Collecting the Data

Graphing the Results• Independent Variable: The Variable that we changed during the

experiment. Plotted on the horizontal axis (x)• Dependent Variable: The variable that changes as a result of the

independent variable. The result of the experiment. EX: Reaction time (time it takes tablet to dissolve.) Plotted on the vertical axis (y)

Analyzing Results and Conclusion• Reaction time decreased as temperature increased• Reaction time decreased as surface area increased• Conclusion: Our experiment supported our hypothesis that the

rate of chemical change will increase as the temperature and surface area of the reactant increases

Although our experiment supported our hypothesis, it did not PROVE our conclusion…WHY?

Theories• Theory: A general explanation of a set of observations based on

testing hypotheses. Explains how things happen in nature.• A theory is supported by lots of data collected from many

different experiments and observations• Theories can change over time as scientists gather more info• EXAMPLE: Scientists in the past thought that the world was flat

and that the sun revolved around the earth, later through scientific observation and processes, they realized that the earth is round and that the earth revolves around the sun

Scientific Laws• An action or sets of actions about the universe that has always

been observed as true. Must be simple, universal, and absolute.• EXAMPLE: Law of gravity, E=MC(squared), etc.