Answer:
1. Dissolving powder in milk - Chemical
- It is chemical because the milk has changed on a molecular level
2. Toasting bread - Chemical
- It is chemical because adding heat to the bread cooks it, therefore
changing it on a molecular level
3. Melting cheese - Physical
- It is physical because the physical appearance was the only change
4. Slicing apples or bannanas - Physical
- It is physical because the physical appearance was the only change
5. Frying an egg - Chemical
- It is chemical because new particles were formed
6. Milk souring - Chemical
- It is chemical because it is forming a new product (lactic acid)
Explanation:
Physical Change occurs when the particles of a substance become rearranged, but do not change into different particles.
Chemical change occurs when a new substance is formed. This process is irreversable.
HBr and HF are both monoprotic Arrhenius acids—that is, in aqueous solution, they dissociate and ionize to give hydrogen ions. A strong acid ionizes completely; a weak acid ionizes partially.
In this case, HBr, being a strong acid, would ionize completely in water to yield H+ and Br- ions. However, HF, being a weak acid, would ionize only to a limited extent: some of the HF molecules will ionize into H+ and F- ions, but most of the HF will remain undissociated.
pH is, by definition, a measurement of the concentration of hydrogen ions in solution (pH = -log[H+]). A higher concentration of hydrogen ions gives a lower pH, while a lower concentration of hydrogen ions gives a higher pH. At 25 °C, a pH of 7 indicates a neutral solution; a pH less than 7 indicates an acidic solution; and a pH greater than 7 indicates a basic solution.
If we have equal concentrations of HBr and HF, then the HBr solution will have a greater concentration of hydrogen ions in solution than the HF solution. Consequently, the pH of the HBr solution will be less than the pH of the HF solution.
Choice A is incorrect: Strong acids like HBr dissociate completely, not partially.
Choice B is incorrect: While the initial concentration of HBr and HF are the same, the H+ concentration in the HBr solution is greater. Since pH is a function of H+ concentration, the pH of the two solutions cannot be the same.
Choice C is correct: A greater H+ concentration gives a lower pH value. The HBr solution has the greater H+ concentration. Thus, the pH of the HBr solution would be less than that of the HF solution.
Choice D is incorrect for the reason why choice C is correct.
Answer:
The rate decreases
Explanation:
When we dissolve a gas in a water, the process is exothermic. This implies that heat is evolved upon dissolution of a gas in water.
Recall from Le Chateliers principle that for exothermic reactions, an increase in temperature favours the reverse reaction. The implication of these is that when the temperature of the gas is increased, less gas will dissolve in water.
Hence increase in temperature decreases the rate of solubility of a gas in water.

<u>Difference </u><u>between </u><u>Atomic </u><u>mass</u><u>, </u><u>relative </u><u>atomic </u><u>mass </u><u>and </u><u>average </u><u>atomic </u><u>mass</u><u> </u><u>:</u><u>-</u>
<h3><u>Atomic </u><u>Mass </u><u>:</u><u>-</u></h3>
- Atomic mass is the mass of neutrons and protons present in the nucleus of an atom .
- It is always calculated for a single element and having direct value
- For isotopes also, the atomic mass is calculated separately . Example :- <u>Carbon </u><u>1</u><u>2</u><u> </u><u>,</u><u> </u><u>carbon </u><u>1</u><u>3</u><u> </u><u>and </u><u>carbon </u><u>1</u><u>4</u><u> </u><u>have </u><u>different </u><u>atomic </u><u>mass</u><u>. </u>
- The SI unit of Atomic mass is " u" and "amu"
<h3>
<u>Relative </u><u>Atomic </u><u>mass </u><u>:</u><u>-</u></h3>
- Relative atomic mass is mean mass of the atoms of an element which is compared to the 1/12th mass of carbon - 12 .
- Carbon - 12 is taken as a relative when we calculate the relative atomic mass of any element
- For calculating relative atomic mass, we need to know the masses, percentage and abundance of all types of elements
- Relative atomic mass is a dimension less quantity
<h3><u>Average </u><u>Atomic </u><u>Mass </u><u>:</u><u>-</u></h3>
- Average atomic mass is the average mass of an atoms of a particular element by considering it's isotopes
- While we calculate average atomic mass is a standardized number. Whereas, Average atomic mass sometimes varies geologically .
- It also includes percentage, abundance and masses of given element .
- In average atomic mass, We do not compare mean value with the 1/12 mass of carbon - 12
- The unit of Average atomic mass is "Amu" or " u " .