Energy

Lesson 1:

• Work energy and power

• Apply mathematical formulas

• Understand the work energy principle

Formulas

• F= ma= kgms⁻²

• d=m

• kgm²s⁻²= joule

• Ek = mv²

• Work = Force * distance

• force = m*a*d = force = mad

• W= fd cos (0)

• p = work / t == W = js⁻¹

• 1 watt is equal to 1 joule / s

Notes:

• Work is just net force applied to an object multiplied by the distance the object moves.

• In reality, work is a vector therefore we have to take into consideration any direction that the forces are applying to

• you are doing work as long as you are applying a positive net force on an object

• if you apply a force but there is no movement there is no work.

• If you pick up an object and move it at a constant velocity there is no work as there is no net force.

• when the force applied to an object is in the same direction as its displacement the work is positive

• example: when you lift a weight vertically you do positive work against the gravitational force

• work is considered negative when the force applied is in the opposite direction to the object displacement

• if you are riding a bicycle and apply the brakes you are doing negative work.

• Zero work: is done when the force applied to an object does not result in any displacement or when the force of the force applied is perpendicular to the direction of the displacement. if you hold a book at a constant height you are doing zero work as the distance (d) is zero

• A watt is the unit of power.

Heat:

• A measure of total energy

• Temperature is only the E_k of a substance molecules

• Temperature is measured with the SI units like Celsius and Kelvin.

Lesson 2:

Density:

• Density is a measure of an object’s mass over the volume of the object.

  • Mass is measured in kg

  • Volume is measured in m³

  • kgm⁻³

• There are several extremely dense and non-dense materials. This can be seen through the groups on the periodic table.

  • Hydrogen is the least dense at about 0.08 kgm⁻³

  • Osmium is the most dense sitting around 22 590 kgm⁻³

Units and symbols:

• There are many units for density but only one is based on the SI system, that is kg⁻³

  • You can express density in gcm⁻³ or kgm⁻³

  • The symbol for density is p (pho)

Lesson 3:

• Be able to describe the states of matter

• describe heat bs temperature

States of matter:

• Solid: rigid fixed shape

• Liquids: not rigid, cannot be compressed but fixed volume

• Gas: can be compressed, with no fixed volume or shape

Notes:

What is kelvin: It is an absolute scale. it cannot be below zero it is as cold as something can possibly get before all atomic movement ceases.

• 0 K is around -273.15 ⁰C

• C + 273.15 = K

The difference between heat and temperature is that heat is a measure of how much internal energy a substance has and is measured in joules.

Temperature is the measure of kinetic energy only and nothing with potential energy.

Absolute zero occurs at a region where all gases would be the same temperature because all gases would exhibit a pressure of zero.

All gases have the same thing in common when they reach the pressure of zero they all have the same temperature.

We tend to measure things to do with energy with calories.

One thousand calories is the amount of energy required to heat 1kg of water by 1 ⁰C

One calorie is required to heat the 1g of water by 1⁰C

• 1 calorie = 4.184 joules

• The equation we use is this Q = mcΔT

  • Q is heat in joules

  • m is the mass of the substance in kg or g

  • c is the specific heat capacity —> in Jg⁻¹C⁻¹ (the amount of energy to raise a unit mass of a substance’s temperature by 1 Celsius or 1 K)

  • T is the temperature in Celsius or Kelvin —> (final temp - initial temp)

Lesson 4:

Buoyancy and Pressure:

Notes:

Pressure is a measurement of how much force per unit area is on a surface.

The units of pressure are:

• Bar

• Pascals

• Atmospheres, ATM

• Tor

• psi

The most common one is Pascal also written as Nm⁻² it is based on the equation Pressure = f/a

• Where a is preferred in m⁻2

Buoyancy:

Buoyancy is the tendency of an object to float in a fluid. It is an upward force exerted by a fluid.

Fluid pressure is the pressure in a static fluid that arises from the weight of the fluid and is given by the expression:

• P_static (fluid) = pgh where →Pa

  • p (rho) = m/V = fluid density →Kgm⁻³

  • g = acceleration of gravity →ms⁻²

  • h = depth of fluid → m

• Air is also considered a fluid

Archimedes principle explains that the buoyant force on any solid object is equal to the weight of the water displayed

The amount of water you displace is equivalent to the mass that you will be lighter in water.

The volume of an object is the amount of water it will displace when submerged in water. In water, the density of water is around 1 gcm⁻³ so each cm³ will displace 1 g of water.

Lesson 5:

To do:

• Go through forces

• Pressure

• Density

• Heat capacity

• Complete the worksheet

• Brief review calorimetry

Lesson 6:

• Latent heat is the heat required to convert a solid into a gas or vapor without a change of temperature

• Cals: