Bacterial contamination can occur within seconds to minutes, depending on various factors such as the type of bacteria and the environment. The most accurate option among the given choices is 5-10 minutes.
Explanation:Bacterial contamination can occur very quickly, often within a matter of seconds or minutes. The actual speed of contamination depends on various factors such as the type of bacteria, the environment, and the presence of favorable conditions for bacterial growth. For example, if a person touches a contaminated surface and then touches their mouth or eyes, the bacteria can be introduced to their body almost immediately. Similarly, food left at room temperature for a few minutes can provide enough time for bacteria to multiply and contaminate the food.
Therefore, among the given options, the most accurate answer would be 5-10 minutes as a broad estimate of how quickly bacterial contamination can occur in certain situations.
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The correct answer is c. 10-20 seconds. bacterial contamination can occur in 10-20 seconds.
Bacterial contamination can occur very quickly, especially when proper food handling and hygiene practices are not followed. Cross-contamination between raw and cooked foods, or foods that will not be cooked, such as salads, can happen in a matter of seconds if they come into contact with contaminated surfaces, utensils, or hands. The time frame of 10-20 seconds is consistent with the rapid nature of bacterial transfer.
To prevent such contamination, it is crucial to maintain cleanliness in food preparation areas, wash hands thoroughly before handling food, and keep raw and cooked foods separate. The other options, 5-10 seconds, 5-10 minutes, and 10-20 minutes, do not accurately represent the speed at which bacterial contamination can occur, with the fastest being within seconds under the right conditions.
what is the definition of radiant energy
Answer:
Radiant energy is energy that travels by waves or particles, particularly electromagnetic radiation such as heat or x-rays.
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Radiant energy is energy emitted and transmitted as waves rather than matter. It consists of the full spectrum of electromagnetic waves, including visible light, and is essential for various biological processes such as the production of vitamin D in the human body.
Explanation:Radiant energy is energy emitted and transmitted as waves rather than matter. These waves vary in length from long radio waves and microwaves to short gamma waves emitted from decaying atomic nuclei. The full spectrum of radiant energy is referred to as the electromagnetic spectrum. The body uses the ultraviolet energy of sunlight to convert a compound in skin cells to vitamin D, which is essential to human functioning. The human eye evolved to see the wavelengths that comprise the colors of the rainbow, from red to violet, so that range in the spectrum is called "visible light."
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transverse waves in a sentence
Answer: transverse wave is a progressive wave whose oscillations are perpendicular to the direction of the wave
Explanation:
How many formula units are in 3.6 grams of NaCl?
Answer: 3.914 x 10^22 formula units
Explanation:
number of moles of NaCl = 3.8g/58.5g/mol = 0.065 moles
Formula units of NaCl = 0.065 x 6.022 x 10^23 = 3.914 x 10^22
Formula units are defined as the empirical formula of an ionic or covalent compound used to express them as independent entities.
Given that:
Given mass = 3.6 gram
Formula units =?
Molecular mass of NaCl = 58.44 g/mol
As we know:
[tex]\rm moles &= \dfrac{\text{given mass}}{molecular\; mass}[/tex]
[tex]\rm moles = \dfrac{3.6}{58.44}\\\\\rm moles = 0.061\\[/tex]
Now,
1 mole = [tex]6.022 \times 10^{23}[/tex]
[tex]\begin{aligned} \rm 0.061\; moles &= 0.061 \times 6.022 \times 10^{23}\\\\\rm moles &=3.67 \times 10^{22}\end[/tex]
Thus, the formula units in the 3.6 grams of NaCl is [tex]3.67 \times 10^{22}[/tex].
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which group of elements have almost no reactivity
Answer:
Group 0 the noble gases
Answer: group zero (noble or rare)
Explanation:
What is a semiconductor?
A. A conductor that operates only at low temperatures.
B. A conductor that conducts electricity faster than common metals.
C. A conductor that has less conductivity than do metallic
conductors
D. A substance that completely blocks the flow of electricity.
Answer:
C. A conductor that has less conductivity than do metallic
conductors
Explanation:
Semi means less
Answer:
C. A conductor that has less conductivity than metallic conductors
Explanation:
A semiconductor can conduct electricity, so they're not insulators, but the conductivity isn't as effective as a metal.
An object accelerates 3.0 m/s2 when a force of 6.0 Newton’s is applied to it. What is the mass of the object?
Answer:2kg
Explanation:
Mass =?
Acceleration = 3.0 m/s2
Force = 6.0N
Force = Mass x Acceleration
6 = Mass x 3
Mass =6/3 = 2Kg
how many Fahrenheit degrees seperate the freezing and boiling points of water? what are these two temperatures?
Explanation:
Boiling temperature is 212° F, while freezing is 32 °F, so it would be a difference of 181 degrees.
Hope you have a good day!
In the Fahrenheit scale, water freezes at 32 degrees and boils at 212 degrees. Hence, there are 180 degrees Fahrenheit separating the freezing and boiling points of water.
Explanation:In the Fahrenheit temperature scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point of water is 212 degrees Fahrenheit. To find out how many Fahrenheit degrees separate these two points, we need to subtract the freezing point from the boiling point.
212 (boiling point) - 32 (freezing point) = 180
Therefore, there are 180 degrees Fahrenheit between the freezing and boiling points of water.
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How does heat travel from the sun to a plant in a greenhouse?
Answer: Radiation
Explanation: The sun transfers heat energy through radiation since in a vacuum it does not require any medium to allow heat flow.
Which of the following factors contributes to the increase in ionization energy from left to right across a period?
Answer:
an increase in the number of protons
Explanation:
As one moves from left to right in the periodic table, the protons steadily increase by one across each period. This increase in number of protons implies an increase in the size of the nuclear charge and a consequent increase in electrostatic attraction between the nucleus and the outermost electron. This increased nuclear attraction leads to an increase in ionization energy across the period.
The increased number of proton increase in ionization energy from left to right across a period.
Ionization Energy:
It is the energy that required to take out one electron from the outer shell of an isolated atom.
When we move from left to right in the periodic table, the number of proton increase but the number of shell remain constant.
This increase the strength of attraction between outer most shell's electron and nucleus.
Therefore, the increased number of proton increase in ionization energy from left to right across a period.
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You have a sample of 0.25 mol of unknown gas at STP. Can you predict the volume of the gas, even if you don’t know the identity of the gas ? Can you predict the mass of the sample ? Explain.
Answer:
a. 5.6 L
b. can be find without given mass or Molar mass
Explanation:
Data given:
mole of unknown gas = 0.25 mol
volume of gas = ?
mass of the sample = ?
Solution:
Yes we can find volume of the gas by using its amount of moles.
To find the volume of the gas at STP the following formula can be used
no. of moles = volume of gas / molar volume
Rearrange the above formula
volume of gas = no. of moles x molar volume . . . . . (1)
Where
molar mass of gas = 22.4 L/mol
Put values in equation 1
volume of gas = 0.25 mol x 22.4 (L/mol)
volume of gas = 5.6 L
So the volume of gas is 5.6 L.
_____
Q. Can you predict the mass of the sample?
To find mass of the gas we must know the molar mass of gas.
if we Know the molar mass of gas the by using ideal gas equation we can find mass of unknown gas
ideal gas equation
PV = nRT . . . . . . .(1)
where
n = m/M . . . . . . (2)
by combining equation 1 and 2 we get following equation
PV = m/MRT . . . . . . .(3)
Now by rearranging equation 3 we can find mass of gas or Molar mass of gas. but one value must be given.
Why is a study of basic chemistry essential to
understanding human physiology?
Answer:
Because it describes the chemica
reactions that underlie all body.
Explanation:
Like movement, digestion, the pumping of your heart and even thoughts.
A basic knowledge of chemistry is crucial to understanding human physiology because processes like digestion, respiration, and all bodily functions involve chemical reactions. Concepts of chemistry like atomic structure, elements, molecules and bonds are fundamental in understanding how different nutrients and toxins impact our health and bodily functions. Thus, chemistry is instrumental in understanding human physiology.
Explanation:Basic chemistry is pivotal in understanding human physiology because it forms the framework for examining the workings of the physical body. For example, chemical reactions occur when we digest food, breathe, or perform any bodily function. These reactions are dependent on the principles of chemistry. Understanding concepts such as atomic structures, elements, molecules, and bonds are fundamentals of chemistry that help us grasp how differing nutrients and toxins affect the body's performance and health. Additionally, the physiology of cell and its function, nerve transmission, muscle contraction, and homeostasis, they all have biochemical basis. Therefore, studying basic chemistry is an essential stepping stone to grasp the understanding of human physiology.
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–5 5/6 ÷ (–2 1/6)
divide.
Answer:
2 9/13
Explanation:
First cancel the minus
then convert the Mixed fractions to improper fractions, you have
35/6 divided by 13/6
it becomes 35/6 x 13/6
when you cancel out, you’ll be left with 35/13 which Is 2 9/13
3. For the reaction: 2X + 3Y 3Z, the combination of 2.00 moles of X with 2.00
moles of Y produces 1.75 moles of Z. What is the percent yield of this reaction?
Answer:
Explanation:
For the reaction: 2X + 3Y = 3Z, the combination of 2.00 moles of X with 2.00
moles of Y produces 1.75 moles of Z
2 mol 2 mol 1.75 mol
2X + 3Y = 3Z
need 2 mol 3 mol to give 3 mol
3 mol Z/3 mol Y= 1 to 1
should get 2 mol Z
1.75/2 =87.5 % yield
87.5 % per cent yield of this reaction when the combination of 2.00 moles of X with 2.0 moles of Y produces 1.75 moles of Z
What are moles?A mole is defined as 6.02214076 × [tex]10^{23}[/tex]of some chemical unit, be it atoms, molecules, ions, or others. The mole is a convenient unit to use because of the great number of atoms, molecules, or others in any substance.
For the reaction: 2X + 3Y = 3Z, the combination of 2.00 moles of X with 2.00 moles of Y produce 1.75 moles of Z.
2 mol + 2 mol = 1.75 mol
2X + 3Y = 3Z
Need 2 mol 3 mol to give 3 mol
3 mol Z ÷3 mol Y= 1 ÷ 1
should get 2 mol Z
The per cent yield of this reaction:
1.75 ÷ 2 = 87.5 % yield
Hence, 87.5 % per cent yield of this reaction.
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Beryllium magnesium and calcium all are located in the alkaline earth group which of these characteristics do these elements have in common?
Answer:
They all have similar compounds when combine with oxygen.
Explanation:
Alkaline earth metals are present in group 2 of periodic table. There are six elements in second group. Beryllium, magnesium, calcium, strontium, barium and radium.
All have two valance electrons but in different energy levels.
Electronic configuration of Beryllium:
Be = [He] 2s²
Electronic configuration of magnesium.
Mg = [Ne] 3s²
Electronic configuration of calcium.
Ca = [Ar] 4s²
They are present in group two and have same number of valance electrons (two valance electrons) and show oxidation state +2 by loosing two valance electrons. They also show similar reactivity.
They react with oxygen and form oxide.
2Be + O₂ → 2BeO
2Mg + O₂ → 2MgO
2Ca + O₂ → 2CaO
this oxide form hydroxide when react with water,
BeO + H₂O → Be(OH)₂
MgO + H₂O → Mg(OH)₂
CaO + H₂O → Ca(OH)₂
With sulfur,
Mg + S → MgS
Ca + S → CaS
Ba + S → BaS
Which learning theory is based on associative learning?
what is kinetic energy
Answer:
kinetic energy is the energy of movement
Explanation:
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Answer:
Kinetic energy is the energy possessed by a body due to its motion. In other words, any moving body or object has kinetic energy.
Explanation:KE=1/2mv²
Where KE is the kinetic energy in (in J)
m is the mass of the body (in kg)
v is the speed of the body (ms-¹)
From the equation, we can see that for two objects moving at different speeds, the faster object has a greater KE. Similarly, for two objects of different masses moving at the same speed, the object of greater mass has a greater KE.
How can a scientific law be expressed as a mathematical equation?
Answer:
A scientific law is a statement that can usually be expressed as a mathematical equation that describes an occurrence in nature. At the time a law is made there are no exceptions to the law. However, over time, conditions may be observed that make the law true only in certain conditions.
Explanation:
Answer:
Turn it into a equation
Explanation:
Simple
A decomposition occurs when you open a can or bottle of soda. Carbonic acid. H.CO, is in carbonated beverages. It
decomposes into carbon dioxide and water. If you leave an open soda can out for a long time, it loses its fizz Which equation
represents the chemical equation for this reaction?
H20-602 - H2CO:
H2003 - H20 - CO2
H₂CO₃ + H₂O - CO₂
2H2CO3 - 2H20 - 2002
Answer:
H₂CO₃→H₂O + CO₂
Exphlanation:
Soda is carbonated water. It contains carbon dioxide dissolved in water , which is carbonic acid. On opening the soda, the carbonic acid undergoes the reverse reaction and releases carbon dioxide in the air . The soda is thus left with just water and loses it's fizz.
Answer:
H₂CO₃→H₂O + CO₂
worked it out
Using the periodic table, complete the following.
Element: oxygen
symbol: 02
Molecular weight:
Mass of one mole:
g/mol
Explanation:
Oxygen
It is placed in group 16 and period 2 rd .Its atomic number is = 8No. of protons = 8No. of electrons =8 Electronic configuration=2,6Valence shell = LValence electron = 6valency =-2Its isotopes are O-16,O-17,O-18 It exist as diatomic gas (O₂)Its atomic mass is =16g Its molecular mass = 16 x 2 =32g It is supporter of combustion . It is necessary for survival .If energy or mass can neither be created nor be destroyed then how is there electrical energy and potential energy and everything in the world possible?
Answer:
Energy can transfer (convert) from one form to other.
Explanation:
Law of Conservation of Energy : It states that energy can neither be created nor destroyed in a chemical reaction but can be converted from one from to another.
Potential Energy(P.E) : Energy possessed by the object due to its position and size.Near the ground it attains zero value or close to it.
Kinetic Energy(K.E) : The energy possessed by the object due to its speed .When the object is in motion it has kinetic energy
For example :
When a stone is placed (rest) at some height on the top of the building . It has only potential energy .The potential energy at this point is calculated by
P = mgh
Now , when the the stone is released. It falls to the ground . During its motion towards the ground , its speed increases but the distance of stone from the ground decreases .
Hence the Object in between the ground and building has both K.E and P.E
K.E + P.E = mgh + 1/2 mv^2
If the object reaches just near the ground. Its kinetic energy is maximum but potential energy is almost zero . So at this point ,
K.E = 1/2 mv^2
Hence the Same potential energy is converted into kinetic energy while reaching the ground .
The object itself has not created the energy in between the motion.Neither its energy goes to zero.
Please answerrrrrrrr
Answer:1. Energy 2. Medium 3. Original position 4. Waves 5. Matter
Explanation:
calculate the mass of solid sodium that's needed to fully react with 4.0 L of chlorine gas at STP.
_Na ₍s₎+_Cl₂₍g₎ →_NaCl₍aq₎
Answer: 8.28g Na
Explanation: use ideal gas law
PV= nRT
Solve for moles of Cl2
n= PV/ RT
Substitute:
= 1 atm x 4.0 L / 0.08205 L.atm/ mol. K x 273 K
= 0.18 moles Cl2
Do stoichiometry to solve for m of Na
2 Na + Cl2 => 2 NaCl2
=0.18 moles Cl2 x 2 mol Na/ 1 mol Cl2 x 23g Na / 1 mol Na
= 8.28 g Na.
the density of carbon tetrachloride, CCl4, is 1.59 grams/ml. calculate the volume of 100.0 grams of CCl4
Answer:
63 mL
Explanation:
Data given:
density of CCl₄ = 1.59 g/mL
mass of CCl₄ = 100.0 g
Volume = ?
Solution:
To calculate density formula will be used
d = m/v
rearrange the above equation
v = m/d . . . . . . (1)
where
d = density
m = mass
v = volume
put values in above formula 1
v = 100.0 g / 1.59 g/mL
v = 63 mL
so. the volume of CCl₄ = 63 mL
The given values:
Mass, m = 100.0 gDensity, d = 1.59 g/mLAs we know,
→ [tex]Volume = \frac{Mass}{Density}[/tex]
By substituting the given values, we get
[tex]= \frac{100.0}{1.59}[/tex]
[tex]= 63 \ mL[/tex]
Thus the above response is appropriate.
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when the pH of a solution changes from a ph of 5 to a ph of 3, the hydronium ion concentration is
Answer:the hydronium ion changes from 1x10^-5 to 1x10^-3M
Explanation:Please see attachment for explanation
Which answer below correctly identifies the type of change and the explanation for the boiling of water?
physical change because even though the change caused the temperature of the water to increase,
the water's physical properties remained exactly the same
physical change because even though gas formation was observed, the water was undergoing a
state change, which means that its original properties are preserved
chemical change because gas formation was observed, which indicated that the water was
transformed into a different substance
chemical change because a temperature change was observed, which indicated that the water was
transformed into a different substance
DONE
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9 of 20
Answer:
Boiling of water is physical change.
Explanation:
Physical change is that change where the form of the matter is altered, but there is no change in the chemical composition . It is also a reversible change.
When water boils it changes it's state form liquid to gas. But it's chemical composition is the same.Also on cooling water vapor we can get the water again.So the change is reversible.So boiling of water is a physical change.
What is an open-loop system?
A.
A group of related objects that do not send out or receive feedback and cannot modify themselves
B.
Any device used to extend human capability
C.
A group of related objects that make up a larger system
D.
A group of related objects that send out and receive feedback and can modify themselves
Answer:
An open-loop system is described as:
Explanation:
A. A group of related objects that do not send out or receive feedback and cannot modify themselves
In an open-loop system:
- The system does not receive feedback on its output to make adjustments.
- The system's operation is predefined and does not depend on external input.
- There is no mechanism in place to modify the system based on the output.
An example of an open-loop system is a traditional thermostat that operates based on pre-set temperature settings without actively sensing the actual room temperature and adjusting accordingly. hope this helps!!
Which of the following is true about two objects of the same mass when they have a non-sticky collision?
a. when the objects collide, the momentum of each will become zero
b. when the objects collide, they will trade velocities
c. when the objects collide, each object will then have the sum of the original momentum’s
The following diagram of a pendulum shows the path it takes as it swings back and forth.
As the pendulum moves from point 1 to point 3, what happens to its mechanical energy?
A.
Potential energy is converted to kinetic energy and back again.
B.
Kinetic energy is converted to potential energy only once.
C.
Potential energy is converted to kinetic energy only once.
D.
Kinetic energy is converted to potential energy and back again.
Final answer:
The pendulum's mechanical energy alternates between potential energy and kinetic energy as it swings from point 1 to 3, with potential energy being maximum at the endpoints and kinetic energy maximum at the midpoint.
Explanation:
As a pendulum swings from point 1 to point 3, its mechanical energy experiences a transformation between two forms: potential energy (PE) and kinetic energy (KE). At the highest points in its swing (points 1 and 3), the pendulum's potential energy is at a maximum because it's the highest from the equilibrium position and its kinetic energy is zero as the velocity is zero. As it passes through the mid-point (point 2), the pendulum has its maximum kinetic energy because it's moving the fastest and its potential energy is at a minimum. Therefore, the correct answer is A: Potential energy is converted to kinetic energy and back again. This is because as the pendulum falls from point 1, the potential energy is being converted into kinetic energy until it reaches point 2, where kinetic energy is maximum. As it moves from point 2 to point 3, kinetic energy is converted back into potential energy.
Which of the following examples is a sign
that a chemical change is occurring?
A. the substance seems to have disappeared
B. the state of the matter has changed
C. the production of heat, light, and smoke
Answer: C. The production of heat, light and smoke
Explanation: In a chemical reaction taking place several evidence are the presence of light emission and heat is generated in the reaction. Smoke is also an indication when a chemical reaction is happening such as combustion reaction.
find the density of a material given when a 5.03 g sample is place in 47.54 mL of water the water level rises to 50.78 mL
Answer:
The density of a material given is 1.55 g/mL
Explanation:
Density = Mass per unit volume of the substance .
[tex]Density=\frac{mass}{Volume}[/tex]
Initial Volume of water = 47.54 mL
Total volume = Volume of water + material = 50.78 mL
Volume of material = Total volume - volume of water
Volume of material = 50.78 - 47.54 = 3.24 mL
Volume of material = 3.24 mL
Mass of the material = 5.03 g
[tex]Density=\frac{mass}{Volume}[/tex]
[tex]Density=\frac{5.03}{3.24}[/tex]
[tex]Density = 1.55g/mL[/tex]
The density of a material given is 1.55 g/mL