Changes: Physical or Chemical?

Question 1 

Classify the following changes as physical or chemical. Wood burns to ashes; water begins to boil; grass grows; a rock is crushed to powder. 

Chemical; physical; physical; physical 

Physical; physical; chemical; physical 

Chemical; physical; chemical; chemical 

Chemical; physical; chemical; physical 

Question 2 

Oxygen O 2 , is certainly good for you. Does it follow that if small amounts of oxygen are good for you then large amounts of oxygen would be especially good for you? 

No. Large amount of oxygen will absorb hydrogen from the body and increase the amount of water in the body causing an imbalance in electrolytes. 

Yes. Increased oxygenation of the bloodstream is good for you and can increase your life span. 

No. Breathing 100% oxygen for extended periods of time can be damaging to the body. 

Yes. This is the reason patients are given (100%) oxygen during medical procedure. 

Question 3 

If you eat metallic sodium or inhale chlorine gas, you stand a strong chance of dying. Let these two elements react with each other, however, and you can safely sprinkle the compound on your popcorn for better taste. What is going on? 

Sodium and chlorine from the elemental form is more concentrated than the sodium and chlorine we get from sodium chloride. 

All elements are inherently dangerous. 

Sodium chloride has nothing in common with sodium and chlorine. 

After these two elements react they lose the potential energy to cause harm. 

Question 4 

Each night you measure your height just before going to bed. When you arise each morning you measure your height again and consistently find that are 1 inch taller that you were the night before but only as tall as you were hours ago! Is what happens to your body in this instance best described as a physical change or a chemical change? 

Chemical change because it involves changes in your bone structure. 

Physical change because water expands as it freezes 

Chemical change because it involves your body 

Physical change because it readily reverses. 

Question 5 

A skillet is lined with a thin layer of cooking oil followed by a layer of unpopped popcorn kernels. Upon heating the kernels all pop thereby escaping the skillet. Which of the following physical and/or chemical changes occur? 

The water within each kernel is heated to the point it would turn into water vapour as the kernel popped (physical change). 

The starches within the kernel are cooked by the high temperatures (chemical change). 

Both the water within each kernel is heated to the point that it would turn into water vapour as the kernel popped (physical change) and the starches within the kernel are cooked by the high temperature (chemical change) occur. 

Physical change and chemical changes cannot occur without a real chemical reaction. 

Question 6 

If carbonic acid (H 2 CO 3 ) were to undergo ionization, what would one of the products be? 

CO 3 -1 

H 2 O 

CO 2 

CO 3 -2 

H - 

Question 7 

Distinguish between a metal and a metal containing compound. 

There is no distinction between the two. 

Only one of these occurs naturally. 

Only one of these contains covalent bonds. 

Only one of these contains ionic bonds. 

Question 8 

Chlorine, Cl 2 , is a gas at room temperature, but bromine, Br 2 , is a liquid. Explain. 

Bromine atoms are larger and this makes the formation of induced dipole-induced dipole attractions more favorable. 

Chlorine atoms are larger and this makes the formation of induced dipole-induced dipole attractions more favourable. 

The smaller chlorine molecules are able to pack together in a tighter physical orientation. 

The bromine ions are held together by ionic bonds. 

Question 9 

Given the following diagram, describe what happens electronically between these two molecules. 

Oxygen B becomes slightly positively charged due to the electron on the water molecule. 

Oxygen A becomes slightly positively charged due to the electron on the water molecule. 

Oxygen W becomes slightly positively charged due to the oxygen molecule. 

None of these. 

Question 10 

If the ionic is stronger than a dipole-dipole interaction, how can water dissolve an ionic compound? 

The in-dipole interactions of a bunch of water molecules gang up on the strong ionic bond and pull it into the solution. 

The ionic bond is weakened by the ion-dipole interactions and ionic repulsion ejects the ions the crystal. 

The ions never overcome their interatomic and therefore are not soluble. 

None of these.