chemistry Flashcards
(44 cards)
Benzene melts at 5.5°C and boils at 80.1°C. Which one of the following statements is true about benzene?
A - The only movement that the particles in benzene have at a temperature of 20°C is vibration about a fixed point.
B - At 100°C, the particles in benzene are well scattered and moving at random.
C - At 0°C, benzene is a liquid.
D - If you cooled benzene from 100°C to 50°C, the change of state that happens at 80.1°C is called sublimation
C - at 0 degrees, benzene is a liquid
the change of state which happens when a purple vapour turns into a purple solid on cooling.
sublimation
the change of state which happens when a few drops of water on a bench gradually disappear.
evaporation
the change of state which happens when colourless liquid naphthalene turns into white crystals.
freezing
Neutral atoms of the same element contain
equal numbers of protons and electrons.
Which one of the following statements about particles in solids and liquids is not true?
A - When a solid is heated, the particles vibrate faster and faster until the forces holding them together are broken, and they become free to move around.
B - Particles in a liquid are quite closely packed but have some freedom to move around.
C - When a liquid is heated, the heat energy makes the particles lighter, which is why they escape more easily from the surface of a hot liquid than a cold one.
D - For most substances, the particles in the liquid are slightly further apart than they are in the solid, and so the liquid is less dense than the solid
C - When a liquid is heated, the heat energy makes the particles lighter, which is why they escape more easily from the surface of a hot liquid than a cold one.
what element has 2 electrons on the inner ring and seven on the outer ring?
florine
what electronic structures represents sulfur
2,8,6
How many electrons are there in the outer level of a strontium atom? The atomic number of strontium is 38.
2 electrons
Which one of the following electronic structures does not represent a noble gas?
A 2,8
B 2
C 2,8,8,8
D 2,8,8,2
D - 2,8,8,2
A particle consisted of a nucleus with 11 protons and 12 neutrons. Around the outside of it were 10 electrons arranged in two levels: 2,8. Which one of the following statements is not true?
A - The mass number of the particle is 23.
B - The particle isn’t a neutral atom. It has a charge of +1.
C - The particle has a noble gas structure of its electrons.
D - The particle is a neon atom.
D - the particle is a neon atom
Uranium-235, an isotope of uranium with a mass number of 235 and an atomic number of 92, is radioactive. It has an unstable nucleus which loses an alpha-particle. Alpha-particles consist of 2 protons and 2 neutrons. Which atom is produced during this process in addition to the alpha-particle?
thorium
describe the plum pudding model of the atom
The atom is a ball of positive charge with negatively charged electrons embedded in it, like plums in a pudding. The overall charge is neutral.
atoms contain: protons, electrons and neutrons. Put them in order of their discovery.
- electron
2.proton
3.neutron
Predict the number of outer shell electrons in an atom of tennessine. Give one reason for your answer.
7 as Tennessine (Ts) is in Group 17 of the periodic table, and all Group 17 elements have 7 electrons in their outer shell.
Tennessine was first identified by a small group of scientists in 2010.
Suggest one reason why tennessine was not accepted as a new element by other scientists until 2015.
Other scientists could not repeat the experiment or confirm the results, so more evidence was needed to prove tennessine was a new element.
what are isotopes
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. They have the same atomic number but different mass numbers.
How do you calculate the relative atomic mass (Aᵣ) of an element with isotopes?
Multiply each isotope’s mass number by its percentage abundance, add the results, then divide by 100.
What happens to the ice at stage B (the flat) of the heating curve?
melting
Why does the temperature of the water stop rising at 23°C (stage D)?
Because it has reached room temperature
How do molecules move at stage A (solid)?
they vibrate around fixed points
How do molecules move at stage C (liquid to gas transition)?
They move in straight lines, colliding occasionally.
A student investigated the rate of this reaction.
This is the method used.
- Add 50 cm³ of 2.0 mol/dm³ hydrogen peroxide solution to a conical flask.
- Add 1.0 g of manganese dioxide to the conical flask.
- Place the conical flask on a balance and start a timer.
- Record the total mass lost from the conical flask every 20 seconds for 180 seconds.
Explain why the mass of the conical flask and contents decreased.
The mass decreased because oxygen gas was produced in the reaction.The gas escaped from the flask, causing a loss in mass.
What does ice floating in water show about its density compared to water?
Ice is less dense than water.
