Answer:
below
Explanation:
1. B. removing heat.
The process of changing a gas into a liquid is called condensation. It occurs when the gas loses heat energy and its particles slow down and come closer together, eventually forming a liquid. Therefore, by removing heat from a gas, it can be changed into a liquid.
2. D. Smashing an object into many pieces is a physical change.
Smashing an object into many pieces does not change the chemical composition of the object. It only changes its physical appearance or state. A physical change is a change in the state or appearance of matter without any change in its chemical composition. Therefore, smashing an object into many pieces is a physical change.
3. No fixed volume or shape: gas
Fixed volume and shape: solid
Fixed volume but no fixed shape : liquid
4. C. Melting is a physical change.
Melting is the process of changing a solid substance into a liquid by heating it to its melting point. During this process, there is no change in the chemical composition of the substance, only a change in its physical state from solid to liquid. Therefore, melting is a physical change.Option A is incorrect because melting does not involve any biological process.
Option B is incorrect because melting does not result in any chemical reaction that alters the composition of the substance.
Option D is incorrect because melting is a natural physical phenomenon that occurs due to changes in temperature or pressure.
5. B. The new substance is different from the beginning substance.
In a chemical change, a chemical reaction occurs, which involves the breaking and formation of chemical bonds between atoms or molecules. This results in the formation of one or more new substances with different chemical properties than the original substances.
During a chemical change, the original substances are converted into new substances that have different physical and chemical properties, such as color, texture, odor, melting and boiling points, solubility, reactivity, etc. Therefore, the new substance is different from the beginning substance.
6. A. Temperature.
Temperature is the primary factor responsible for the form of matter. At different temperatures, matter exists in different states:
- At low temperatures, matter exists as a solid because the particles are tightly packed and have low energy, which keeps them in a fixed position.
- At higher temperatures, matter exists as a liquid because the particles have enough energy to move past each other but are still close together.
- At even higher temperatures, matter exists as a gas because the particles have enough energy to overcome the attractive forces between them and move independently.
Pressure can also influence the form of matter, but temperature is the primary factor that determines the state of matter. Weather and time are not factors that directly influence the form of matter.
7. B. All solid substances require the same temperature to melt them.
This statement is false. Different solid substances have different melting points, which is the temperature at which they change from a solid to a liquid. The melting point depends on the chemical composition and structure of the substance. Therefore, different solid substances require different temperatures to melt them.
Option A is a true statement because different solid substances have different melting points.
Option C is a true statement because heat can be used to change the physical property of an object, such as melting or boiling it.
8. C. Paper burning into ash.
This is a chemical change because burning paper involves a chemical reaction in which the cellulose fibers in paper combine with oxygen in the air to form new substances, such as water vapor, carbon dioxide, and ash. The chemical composition of the paper changes, and it cannot be reversed.
Option A is a physical change because melting ice into water involves only a change in physical state, not a change in chemical composition.
Option B is a physical change because breaking an object into pieces only changes its physical appearance, not its chemical composition.
Option D is a physical change because water changing to steam involves only a change in physical state, not a change in chemical composition.
9. C. When heat changes the chemical composition of an object.
Heat can produce a chemical change when it is used to break or form chemical bonds between atoms or molecules, resulting in a change in the chemical composition of the substance. This can lead to the formation of new substances with different chemical properties than the original substance. Therefore, option C is the correct statement.
Option A is incorrect because heat energy transfer can produce a physical change, such as melting or boiling, but not necessarily a chemical change.
Option B is incorrect because heat changing ice into liquid water is a physical change, not a chemical change.
Option D is incorrect because observing heat in an experiment does not necessarily produce a chemical change.
A student used 0.17 grams of Alka Seltzer for their experiment. What's the mass of sodium bicarbonate (NaHCO3) in their sample?
Answer:
To find the mass of sodium bicarbonate (NaHCO3) in a sample of Alka Seltzer that weighs 0.17 grams, we need to know the percentage of NaHCO3 in Alka Seltzer. This information is usually provided on the label of the product. Once we know the percentage of NaHCO3, we can use the following formula to calculate the mass of NaHCO3 in the sample:
mass of NaHCO3 = sample mass (in grams) x % NaHCO3 / 100
For example, if the percentage of NaHCO3 in Alka Seltzer is 50%, then the mass of NaHCO3 in a 0.17 gram sample would be:
mass of NaHCO3 = 0.17 x 50 / 100 = 0.085 grams
Therefore, the mass of sodium bicarbonate in the student's 0.17 gram sample of Alka Seltzer depends on the percentage of NaHCO3 in the Alka Seltzer, which should be provided on the product label.
Explanation:
What mass of oxalic acid is required to prepare 0.01 N solution in 5 liters?
Answer:
The mass of oxalic acid required to prepare 0.01 N solution in 5 L is 0.78 g.
Explanation:
