Term - Questions | Definition - Answer |
Observation | usually leads into developing a question or problem answered by scientific investigation; is often research based |
Question or Problem | a statement that addresses the observation of the investigator which is written in question format |
Hypothesis | an educated guess or a statement of explanation that must be testable and stated using an If.....then format |
Prediction | a logical statement of the expected outcome of an experiment assuming that the hypothesis is supported |
Variable | a factor capable of change in scientific experimentation |
Independent variable | the factor that is changed or tested in an experiment |
Dependent variable | the factor that is measured in an experiment or the responding variable |
Controlled variable | the experimental "constants" that must remain the same in an experiment. |
Experiment | a test designed to support or reject a hypothesis by pinpointing a cause-and-effect relationship. Most experiments in science are controlled experiments that have two groups and follow a set procedure or step by step instructions. |
Control group | the group that does not get special treatment; represents the norm for comparison of experimental results |
Experimental group | the group that receives the independent variable or special treatment |
Results/ Data | the numerical information collected about what happened in an experiment is organized or graphs so that analysis can lead to forming a conclusion |
Mean | the average score; total sum of scores added and divided by the number of scores |
Median | the middle score or the two middle scores divided by two |
Mode | the most frequently occurring score |
Conclusion | a statement of analysis (data-based) that usually supports ( a hypothesis can not be "proven) or rejects a hypothesis |
Communication/ Report Results | scientists share their research findings on a global basis using computer technology or in scientific journals |
Theory | an explanation that has been extensively tested and verified many times with peer reviews - can be subject to change but are usually not |
Law | a scientific principle that appears to be without exception and not subject to change. |
Atoms | the building blocks of matter |
Atoms Central Nucleus | contains most o the atom's mass |
Central Nucleus contains: | protons; positively charged; neutrons; no charge |
Electrons | negatively charged; found in orbital (or energy levels or shells) outside the nucleus |
Uncharged Atom | the number of protons equals the number of electrons |
Element | substance composed of only one type of atom |
Periodic Table of the Elements | organizes all of the elements based on their number of protons, and their chemical properties |
Element Symbol | each element is represented by a one or two letter chemical symbol |
Isotope | extra neutrons in the nucleus |
Charged atoms or ions | atoms that gain or lost electrons |
Negative ions | atoms that gain electorns |
Positive ions | lose electrons |
Elements | pure substances made of only one kind of atom |
Period on Periodic table | corresponds with the filling of each energy level |
Group on Periodic table | corresponds with the number of electrons in the outermost energy level |
Combination of atoms | atoms combine in definite proportions or rations according to the oxidation or valence number |
Combination of atoms | tell what the combining ability of a given atoms is |
Identification of Valence Number | The best way to tell an atom's valence number is to look at the group number it is in - all atoms of elements in the same group will have the same number of electrons in the outermost energy level or valence shell |
Compounds | forms when different atoms join to form molecule of a new substances in a definite ratio, which is expressed by a molecular formula |
Molecular Formula | tells how many total atoms are found in a molecule |
Forming of Molecules | can be made of the same type of atoms joined together as paired unit such as diatomic element such as hydrogen or oxygen |
When compounds do form the atoms usually combine by: | sharing electrons or transferring electrons |
Ionic Bonds | these bonds are strong bonds made when atoms transfer electrons between the valence shellss |
Covalent Bonds | these are relatively strong bonds made when atoms share electrons in their valence shells. |
Hydrogen Bonds | are very "weak" bonds. Water molecules are held together by these bonds. DNA's bases are held by these temporary bonds |
Water | the most important compound in your body. Over 70% of the human body is made of water. Cells depend on water to make important biochemical reactions happen for them |
Properties of Water | (1) water stores or loses heat slowly. (2) Cohesion and adhesion allows water to bond to itself and different substances. (3) Water is formed from a polar covalent bond. (4) Water has high surface tension. (5) Water can form weak hydrogen bonds. |
Cohesion | allows water molecules to stick together and form round water droplets. Trees move water against gravity to leaves far about grounded by cohesion and capillary action |
Adhesion | allows water to be attracted to many other polar compounds with charged ends. |
Polar covalent bond | The water molecule has partially charged ends because of the electrons are not shared equally. Polarity makes water the universal solvent for making many important solutions in body when the solute or substance dissolved is another polar or ionic molecule |
High Surface Tension | a measure of how difficult it is to break the surface of liquid |
pH | the percentage of hydronium ions in a given solution |
pH - Describes | whether a substance is acid, neutral, or base. Each pH value is different by a power of ten not one. |
Acid | are solutions with a greater number H+ ions than -OH ions (hydroxide ions). The pH value is under 7 |
Acid Examples | lemon juice, vinegar |
Base | solutions with a greater number of -OH ions than H+ ions. The pH value is over 7 |
Base examples | solutions with a greater number of -OH ions than H |
Neutral Solutions | equal numbers of H+ and -OH and have a pH value of 7 |
Neutral Solution Example | Water, Alcohol |
Buffers | weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH |