Y10 Spring Term Physics Roundup

Question 1

What is density?

Answer 1

•The mass per unit of volume of a substance
•Measured in kg/m3
•Dense materials are heavy for their size, i.e. Lead
•To calculate the density, you need to measure the mass and the volume

Question 2

How do you measure volume for a regular object?

Answer 2

• For a regular object (like a cube), measure the dimensions using the right tool and use them to calculate the volume (e.g. l x w x h)

Question 3

How do you measure volume for an irregular object?

Answer 3

•For an irregular object (like a stone), find out the volume of water it displaces using a Eureka can and measuring cylinder

Question 4

What are the properties of a solid?

Answer 4

•Particles are held next to each other in fixed positions
•Particles have the lowest energy
•Fixed shape and volume
•Doesn’t flow
•Much higher density than a gas

Question 5

What are the properties of a liquid?

Answer 5

•Particles move around randomly and are in contact with each other
•Particles have more energy than a solid
•Fixed volume
•Takes shape of container
•Flows
•Much higher density than a gas

Question 6

What are the properties of a gas?

Answer 6

•Particles move randomly, rapidly and are far apart
•Particles have the highest energy
•Volume can change as it spreads out to fill container
•Flows
•Low density

Question 7

What is meant by the term melting point?

Answer 7

•The temperature a pure substance melts at
•A substance will solidify at the same temperature

Question 8

What is meant by the term boiling point?

Answer 8

•The temperature a pure substance boils at
•A substance will condense at the same temperature

Question 9

Define internal energy

Answer 9

•The energy stored by the particles of a substance
•The particles have energy due to their individual motion and positions
•Internal energy = KE due to individual motion relative to each other + PE due to their positions relative to each other
•Higher temperature = higher internal energy
•This is because the KE increases when temp increases
•The PE of a substance increases if it melts or boils

Question 10

Define latent heat

Answer 10

•The energy needed for a substance to change state without changing the temperature

Question 11

What is specific latent heat of fusion?

Answer 11

•The energy needed to melt 1kg of a substance without changing the temperature
•Measured in J/kg
•E = mass x Specific Latent Heat of fusion
•This is the same amount of energy if the substance is going from a liquid to a solid.
•The particles need energy to break free from each other and this energy is the latent heat of fusion

Question 12

What is specific latent heat of vaporisation?

Answer 12

•The energy needed to boil 1kg of a substance without changing its temperature
•Measured in J/kg
•E = mass x Specific Latent Heat of Vaporisation

Question 13

What’s gas pressure?

Answer 13

•This is caused by the particles of a gas colliding randomly with the walls of the container
•In a sealed container, pressure increases if temperature increases because the particles move faster because they have more KE and so hit the surfaces with more force and more times per second
•Smoke particles move unpredictably because gas particles collide with them (Brownian motion)

Question 14

What’s the equation for density?

Answer 14

Density = mass ÷ volume
ρ = m ÷ V

Question 15

What is radioactive decay?

Answer 15

•The nuclei of atoms contain protons and neutrons
•Radioactive nuclei are unstable due to the balance of protons and neutrons. They decay (break down) by releasing nuclear radiation to become stable.
•A random process- we can’t predict or change how it happens.

Question 16

What is nuclear radiation?

Answer 16

•Radiation released when radioactive substances decay
•There are three kinds: alpha (α), beta (β) and gamma (γ)
•The three types of nuclear radiation have different properties

Question 17

How was the nucleus discovered?

Answer 17

•Rutherford fired α particles at gold foil. Most went straight through, some were deflected slightly and a few were deflected by more than 90⁰
•Alpha particles are positively charged so something positively charged in the gold atoms must have been deflecting them.
•Rutherford concluded that most of the mass of an atom must be located in the centre in a positively charged nucleus.
•The plum pudding model of the atom said that the atom was a positively charged sphere with electrons dotted around inside it. Rutherford’s discoveries showed that this couldn’t be correct.

Question 18

What’s the atomic number?

Answer 18

•The number of protons in the nucleus of an atom.
•Sometimes called the proton number
•Usually the smaller number next to the element symbol in the periodic table

Question 19

What’s the mass number?

Answer 19

•The number of protons + the number of neutrons in the nucleus of an atom
•Usually the bigger number next to the element symbol in the periodic table
•No of neutrons in a nucleus = Mass number – Proton number

Question 20

What are the properties of alpha radiation?

Answer 20

•A helium nucleus.
•An alpha particle has a mass of 4 and a charge of +2.
•When a nucleus decays and emits an alpha particle, the mass number of the original nucleus goes down by 4 and the atomic number goes down by 2.
•The decay equation for alpha decay is: top number = -4, bottom number = -2
•Alpha radiation is the most ionising nuclear radiation
•Stopped by paper/skin (least penetrating)
•Range of a few cm in air

Question 21

What are the properties of beta radiation?

Answer 21

•A fast moving electron
•Negatively charged
•Zero (or negligible) mass
•When a nucleus decays and emits a beta particle, the mass number stays the same but the proton number increases by 1 as a neutron changes into a proton.
•The decay equation for beta decay is: top number = no change, bottom number = +1
•Beta radiation is less ionising that alpha but more ionising than gamma
•It is stopped by thin aluminium (second least penetrating)
•Range of around a metre in air

Question 22

What are the properties of gamma radiation?

Answer 22

•A wave of electromagnetic radiation
•No charge as it is a wave
•No mass as it is a wave
•When a nucleus decays and emits a gamma wave, the mass number and atomic number stay the same.
•Gamma radiation is the least ionising nuclear radiation
•Mostly absorbed by thick lead
•Unlimited range in air

Question 23

What is meant by the “half life” of an atom?

Answer 23

•The average time taken for count rate of a radioactive isotope (or the number of radioactive nuclei) to fall by half.
•Half life can be found using a decay curve graph . Find half the initial count rate on the y-axis, draw across to the curve then draw down and read the time off the x-axis.
•Count rate after n half-lives = initial count rate ÷ 2n