This is the mass number A. It shows the number of nucleons (neutrons and protons in the nucleus). It is made up of the atomic number Z and the neutron number N:
A = Z + N
Using the example of helium:
Helium has a mass number A of 4 and the atomic number Z 2, so the atom has 2 neutrons in its nucleus.
A = Z + N
4 = 2 + 2
how can hot water freeze faster then cold water.
Answer:
With the cooler water at the bottom, this uneven temperature distribution creates convection currents that accelerate the cooling process. Even with more ground to cover to freeze, the temperature of the hotter water can drop at a faster rate than the cooler water.
Explanation:
What happens when a chemical hand warmer is unwrapped and starts to work?
A. A physical change absorbs thermal energy.
B. A chemical reaction absorbs thermal energy.
C. A physical change releases thermal energy.
D. A chemical reaction releases thermal energy.
Answer: D. A chemical reaction releases thermal energy.
Explanation:
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What is one key physical difference between transition
metals and poor metals?
А.Atomic mass
B.Hardness
C.Reactivity
D.Charge
Which statement describes a chemical property of mercury?
A. Mercury bonds with oxygen to form a compound found in some
batteries.
B. Mercury is the only metal that is liquid at room temperature.
C. Mercury is much denser than water, so it will sink in water.
D. Mercury is a shiny, silver substance that is found in some
thermometers.
Answer:
It's A
Explanation:
I took the test. For A p e x
What four factors influence the rate of a homogeneous reaction.
Reactant concentration, the physical state of the reactants, surface area, temperature, and the presence of a catalyst are the four factors to influence the rate of a homogeneous reaction.
What is rate of reaction ?The term rate of reaction is defined as the speed at which a chemical reaction takes place. It is also defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time.
Surface area, greater surface area, more collisions are available and then concentration, when increase the concentration then increase the likelihood of reactants colliding. Catalysts increase reaction without itself getting used up.
Thus, The factors to influence the rate of a homogeneous reaction are Reactant concentration, the physical state of the reactants, surface area, temperature, and the presence of a catalyst.
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transition elements have variable valency why
Answer:
The transition elements have their valence electrons in two different sets of orbitals that are (n-1)d and ns. Thus, transition elements show variable valencies due to the involvement of penultimate d shell electrons.
Explanation:
please help , i’m doing a test and i’m really bad at science , lol , thank you !
it cannot be passed to the next generation meaning A chromosome will be eliminated
What is the formula unit for a compound made from Pb4+ and oxygen? (3 points)
PbO2
O2Pb
Pb4O2
O4Pb2
The formula unit of compound made up from Pb4+ and oxygen is PbO2.
The formula unit for a compound made from Pb⁴⁺ and oxygen is PbO₂. Therefore, option (1) is correct.
What is the formula unit?A formula unit represents the lowest whole number ratio of ions in an ionic compound. The formula mass of a substance is the sum of the atomic masses of the ions present in the formula unit of an ionic compound.
Formula unit is the empirical formula of any covalent or ionic solid compound which is used as an independent entity for stoichiometric calculations. Formula mass is also defined as the sum of atomic masses of constituent atoms in an ionic compound.
A molecule is made up of two or more elements that are covalently bonded. Also, the molecular mass gives the mass of a molecule relative to that of a carbon twelve atom which has a mass of twelve units.
As we know the valency of lead is 4 and the valency of oxygen is 2. To satisfy the valency of each other two oxygen combine with one lead (IV). Therefore, the formula unit of the compound is PbO₂.
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how many significant figures does 0.00003 have?
What does gravity do to cause rain to happen?
How does gravity affect water that is on the surface of Earth?
Answer:
When the water droplets in the cloud get too heavy they will fall. Which causes rain to fall. Gravity force pulling the droplets toward the Earth's surface.
It pulls precipitation down form could and pulls water downhill. Gravity pulls denser air and water downwards, forcing less dance air and water to move upwards.
Which of the following best describes what led to London’s ""killer fog"" in 1952? a. Pollution from the air contaminated the water supply which is what killed people. B. Millions of coal fires and stagnant air caused toxic fumes to build up in the air. C. Poor city design led to faulty ventilation in houses. D. Soot from forest and wildfires in the surrounding areas blew over the city. Please select the best answer from the choices provided A B C D.
London’s "killer fog" or The Great Smog of London was the extreme event of air pollution in London. Millions of coal fires and stagnant air were the prime reason for the event.
What was The Great Smog of London?The Great Smog of London was one of the worst events of the air pollution that engulfed the city of England. The industrial air pollutants of the burning coal and high-pressure weather circumstances made the city covered in smog.
This event caused many deaths due to pneumonia and bronchitis in people. The burning of the coal in the industrial plants of the city was the major reason for the smog.
Therefore, option B. millions of coal fires and stagnant air were the main reason for the great smog of London.
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an open flame from a burner heats up the inside of a balloon, allowing it to take flight. How is the pilot able to control the altitude of the balloon.
Answer:
The direction of flight depends on the wind, but the altitude of the balloon can be controlled by changing the temperature of the air inside the envelope. the pilot controls the ascent of the balloon.
Explanation:
:)
True/false: An object acceleration depends on its mass and force. Need help ASAP
When 0. 25 g of the organic compound naphthalene are burned in a bomb calorimeter, the temperature of the water in the calorimeter increases from 24. 00°C to 26. 43 °C. The calorimeter's heat capacity is 4. 13 kJ/°C. How much heat (q_{rxn}) in kilojoules is released by the combustion of the naphthalene?.
-2.5089 kJ is the amount of heat is released by the combustion of the naphthalene.
How we calculate the released heat?Released amount of heat is calculated by using the below formula:
Q = -mcΔT, where
m = mass of naphthalene = 0.25g
c = specific heat of calorimeter = 4.13 kJ/°C
ΔT = change in temperature = 26.43°C - 24°C = 2.43°C
Putting all these values in the above equation, we get
Q = - (0.25 × 4.13 × 2.43) = - 2.5089 kJ
Hence, - 2.5089 kJ heat is released.
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A sample of gas in a rigid container at 1.30 atm and 224 K is heated to 815
K. Assuming that the volume remains constant, what will be the new
pressure of the gas?
With a container at 1.30 atm and 224 K is heated to 815k, the new
the pressure of the gas is mathematically given as
P=4.7299atm
What will be the new pressure of the gas?Question Parameter(s):
A sample of gas in a rigid container at 1.30 atm and 224 K is heated to 815
K.
Generally, the equation for the Ideal gas is mathematically given as
P1/T1=P2/T2
Therefore
1.30/224=P2/815
P=4.7299
In conclusion, new the pressure
P=4.7299atm
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Hi how are you
what do you think about this
A chemical reaction involving substances a and b stops when b is completely used. B is the.
the neutralization reaction gets its name from.the fact that the products of the reaction are
Answer:
Neutral
Explanation:
Neutralization reaction gets its name from the fact that the products of the reaction are _____.
neutral
Determine the mass of the negative electrode at the start of the experiment use figure 3
How do I make element symbols?
Answer: Each element is given its own chemical symbol, like H for hydrogen or O for oxygen. Chemical symbols are usually one or two letters long.
Explanation:Every chemical symbol starts with a capital letter, with the second letter written in lowercase. For example, Mg is the correct symbol for magnesium.
what happens when calcium is treated with water?
form calcium hydroxide and hydrogen gas
Ca + 2H₂O ⇒ Ca(OH)₂ +H₂
PLEASE HELP
Which of the following is a testable scientific question?
Do blue M&Ms taste better than green M&Ms?
1.What is beneath the ground on planets outside our solar system?
2.How does the age of city affect the number of trees in the city?
3.How many houses are in my neighborhood?
NEED HELP ASAP
How can you dissolve more sugar in your coffee, more quickly? In answering this question:
Identify the solute and solvent in the resulting solution
Describe ways to make the sugar dissolve more quickly
Indicate how to maximize the amount of sugar that can be added
Answer:
the solvent =water+coffee powder
the solute =sugar
Explanation:
Breaking up, crushing or grinding a sugar cube before adding it to water increases the sugar's surface area. The more surface area a solute has, the faster it will dissolve because more particles of the sugar can interact with the water. This means the finer the sugar particles meaning a larger surface area which leads to an increase in a faster reaction
I NEED HELP QUICK!! what is the equation to find the percent composition of NaHCO3????
Answer:
???????????
Explanation:
please help !!!!!!!!!!!!!!!!
Answer:
covalen and ionic compound
Compare blue and violet light. which one has the highest energy?
Longest wavelength?
Answer:
Blue
Explanation:
Blue would have the longest wave length because following ROY G BIV the wave length distance between the two decreases as you move from Red to Violet.
Which sentence explains why gases can change volume but liquids cannot?
A. Gravity affects liquid atoms more than gas atoms.
B. The forces holding atoms together are stronger in a liquid than in
a gas.
O c. The forces holding a liquid together are more flexible than those in
a gas.
D. Liquid atoms are more like solid atoms than gas atoms.
Answer:
B. The forces holding atoms together are stronger in a liquid than in
a gas
I hope that this helps!
Select the correct answer. Which sentence is true of all Brønsted-Lowry bases? A. They can donate a hydrogen ion. B. They can accept a hydrogen ion. C. They can produce hydronium. D. They are positively charged. E. They are negatively charged.
Bronsted - Lowry base can accept a hydrogen ion and can produce hydronium.
What are bases?Bases have the pH value in between the range of 7 to 14.
According to the Bronsted - Lowry theory of acid & base, those substance which produces H⁺ ion or proton in the aqueous medium are known as acids and those substance which accepts the H⁺ ion or proton in the aqueous medium are bases. Water is also behave as Bronsted - Lowry base as it accepts the H⁺ ion and forms hydronium ion H₃O⁺.
Hence, option (b) & (c) are correct, i.e. They can accept a hydrogen ion and produce hydronium.
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Please help me with this sheet this is science
A force is an agent that causes a change in the shape or state of motion of an object.
Forces such as gravity, helps keep objects on earth's surface.
What is a force?A force is a pull or push agent which causes a change in the shape or motion of a body.
Forces may or may not result in motion.
Forces can change the position, shape and movement of an object but not its color.
Types of forces include:
frictiongravitymagnetismFriction is a force that slows or stops the motion of an object.
Magnetism is a force is that attracts objects mad of steel, nickel, or cobalt.
Gravity is a force that pulls objects to the centre of the earth.
Example of a pushing force is pushing a car.
Example of pulling force is closing a car door.
Due to the gravitational force acting on all bodies on the earth surface, we do not fall off the earth.
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A ball moving at a 7.0 m/s has a momentum of 98 kg•m/s. What is the ball's mass?
Answer:
Explanation:
Momentum has the formula of kg m/s and is represented by m*v
Formula
momentum= mv
Givens
m =??
v = 7 m/s
mv = 98 kg m/s
Solution
98 = 7 * m
98/7 = m
m = 14 kg