Question

1. When designing an experiment to test your hypothesis, you need at least two different conditions. In the “experimental” condition one or more of the variables are altered to test the hypothesis. The other condition is called the “control” condition. In your own words, what is the purpose of the control condition during the experiment. (3 points)

2. Ionic and covalent bonds between atoms are necessary to build molecules and elements. What is a key difference between ionic bonds and covalent bonds? Hint: The biggest difference has to do with electrons (3 points)

Answer 1

Q1) A control group in an experiment is the group, which do not receive any treatment, this group is kept as a standard to compare with the experimental group with it and see the changes. In an experiment, control group acts as an idle condition or benchmark.

Basically control group have the same characteristics as of the experimental group, but they are not exposed to the studied or experimental condition.

By comparing data obtained from experimental group with control group, the researcher can nullify the effect of external factors (factors other than the studied drug) that might be affecting the overall condition of the participant, these factors are like changes in weather/season etc.

Example of control group:-

Suppose a researcher is studying the effect of a particular drug on the Alzheimer's patients, which can reduce the symptoms of the disease, for this study he takes two groups of sufferers of Alzheimer's, one group is given a standard drug Donepezil and is kept as the control, and the other group the experimental group is given the proposed drug (or the drug to be tasted), and the result is compared with the control group and effectiveness of the new drug is studied.

Q2) Difference between Ionic bond and covalent bond?

There are many types of chemical bonds to bind molecules together, basic chemical bonds are i) ionic bond ii) Covalent bond.

Ionic bond:-

These are the types of bonds in which atoms transfers electrons to each other. To form an ionic bond there must be an electron donor and an electron acceptor. In ionic bond there is complete transfer of valence electrons between atoms, in this case a metal looses an electron to form a positively charged cation and a nonmetal accepts an electron to form a negatively charged anion.

Ionic bond is seen in metals in which they have less electrons in their outermost orbit , they loose these electrons and get noble gas configuration or satisfy octet rule, similarly nonmetals having close to 8 electrons in their outermost orbit or valence shell accepts these electrons and get nobel gas configuration.

Charges on cation or anion are equal to number of electrons donated or received.

Ionic bond occurs between a metal and a nonmetal.

They have high melting and boiling point.

in Ionic bond more than one electron can be donated or received to satisfy the octet rule. In ionic bond net charge of the compound is zero.ionic bonds have no definite shape .

Example of ionic bond :-

In sodium chloride (NaCl) sodium molecule donates the single electron in it's valence shell to satisfy octet rule and becomes a positively charged cation due to loss of electron.at the same time chlorine atom receives one electron to satisfy octet rule and form a negetively charged anion.

Covalent Bond :-

In covalent bond sharing of electrons occur between two atoms.

this type of bonding is found between two atoms of same elements or elements present close to each other in periodic table. usually occurs between two nonmetals.

If atoms have same electronegativity (same affinity for electrons) covalent bond occurs, as both atoms have same affinity for electrons neither has a tendency to donate them so they share electrons to satisfy the octet configuration and become more stable.covalent bonds have a definite shape.

They have low melting and boiling point.

Example of covalent bond :- In Methane carbon has 4 valence electrons, and as it is difficult to donate 4 electrons, it shares these 4 valence electrons with hydrogen atom forming methane.