Energy’s Effect on MATTER

Energy -- the ability to do work

unit = joules

chemical energy: the energy in a substance that can be released by a chemical reaction.

All foods are chemical energy.

Some use heat and feel cold when done reacting.

endothermic

Others give off heat as they are reacting.

exothermic

During chemical reactions:

How do you spot a chemical change?

a change in temperature,

color,

odor,

a precipitate or bubbles forming,

something new has been formed,

some of the original is missing

Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Productswith high energy

Activation energy

Reactants

Reactantswith low energy

Section 2-4

Endothermic

Activation energy

Reactantswith low energy

Activation energy

Low energy reactants become high energy molecules due to the absorption of energy.

Molecules with high energy.

Low energy

High energy

Energy-Releasing Reaction

Productswith low energy.

Products

Activation energy

Reactants withhigh energy.

Reactants

Exothermic

Activation energy

2950 kJ of heat

Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Activation energy

Reactants

Section 2-4

Endothermic feels cold.

Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Activation energy

Reactants

Exothermic feels hot.

What do enzymes do?

Time goes on

Enzymes (a type of catalyst) lower the barrier.

to

2H2O2 O2 + 2H2OEnzyme helper

Conversions or Energy transfers

energy flow: energy being converted from one type to another or from one molecule to another.

transfers of energy:

always result in a loss of heat

conservation of mass: matter cannot be created or destroyed in an isolated system.

conservation of energy: energy cannot be created or destroyed in an isolated system.

The earth is an isolated sy

stem.

Even the best engines are only about 30% efficient.30% of the chemical energy will transfer to mechanical energy.

1 gallon gas = 190 megajoules of chemical energy

70% or 133 megajoules will leave the car as heat.

electromagnetic energy: the energy the sun provides the electromagnetic spectrum.

Also moving electric charges (electricity.)

mechanical energy: motion that does work.

nuclear energy:

fission (break apart) or

fusion (join together) of certain elements.

thermal energy:

heat…infrared of the electromagnetic spectrum.

Heat -- the internal motion of all the atoms of a piece of matter -- it is also formed due to friction --  it causes changes in temperature ( average energy) and phase changes

• Heat causes phase changes. Volume can change during phase changes, but mass remains the same.

• Heat causes expansion of gases, liquids and solids.

Thermal energy can travel in 3 ways.

Electrical to electromagnetic and thermal. Chemical to thermal.

Chemical to mechanicaland thermal.

potential energy: energy stored by virtue of the body’s position.

kinetic energy: the mechanical energy that a body has by virtue of its motion

waterfall -- mechanical energy is converted to electromagnetic energy & thermal energy

lamp --- changes electrical energy to electromagnetic and thermal energies.

engine -- chemical energy is converted to mechanical energy & thermal energy

battery --- changes chemical energy to electromagnetic energy & thermal energy

Matter is always in motion. Solids vibrate. Liquids and gases actually move distances.

A party shop delivers helium-filled balloons to homes and businesses. The owners realize from experience that on hot summer days they should inflate the balloons only three-quarters full. On cold winter days they can fully inflate the balloons.

Which of the following is the best hypothesis to explain this observation?

A. The helium gas is more active in the winter season.

B. Air outside the balloons leaks into the balloons.

C. As the temperature increases, the helium in the balloons expands.

D. Outdoor air pressure in the summer is less than indoor air pressure.

If the temperature of this balloon were to decrease suddenly, how would the balloon change?

A. Its mass would increase.

B. Its mass would decrease.

C. Its volume would increase.

D. Its volume would decrease.

A flowing stream contains water at 18ºC. Cans of soft drinks at 28ºC are lowered into the stream. Which of the following will most likely occur?

A. The soft drink cans will absorb cold energy from the stream’s water.

B. The cans will cool until their temperature is the same as the stream’s.

C. The temperature of the soft drinks will not change since the cans are sealed.

D. The temperature of the cans will decrease to freezing as long as the stream is flowing.

Which numbered process represents condensation?

This diagram of a chemical reaction shows that the reaction is

A endothermic

B exothermic

C reversible

D at equilibrium

Low energy reactants become high energy molecules due to the absorption of energy.

A student heated a 10 g sample of a compound in an open container. A chemical reaction occurred. The mass of the sample was measured again and found to be less than before. Which of the following explains the change in mass of the sample?

A. The heat caused the compound to become less dense.

B. The reaction gave off more heat than was added.

C. Some of the lighter atoms were converted to energy.

D. One of the reaction products was a gas.

In a laboratory, a sealed container with 100g of steam is cooled until all the steam becomes a liquid.

The container is then cooled further until all the water becomes a solid.

Which of the following remains constant during both of these changes?

A. the mass of the water.B. the pressure in the container.C. the total energy of the water.D. the position of the atoms in the container.

A balanced chemical equation has equal numbers of atoms of each type on both sides of the equation. This illustrates the principle of

F conservation of energy.G conservation of mass. H action and reaction.J natural selection.

The illustrations show a conservation of mass experiment.

The solution in the beaker lost mass because---

Some hot water evaporated

An engineer has created a new engine for race cars. It is necessary to know which fuel mixture will allow the engine to run at its peak performance. Which experimental design is best for this investigation?

F Use one fuel mixture on the engine and measure its performance

G Use one fuel mixture on many types of engines and measure their performance

H Use various fuel mixtures on the engine and measure its performance

J Use various fuel mixtures on many types of engines and measure their performance

An inventor claims to have created an internal combustion engine that converts 100 kJ of chemical energy from diesel fuel to 140 kJ of mechanical energy. This claim violates the law of conservation of

F momentum

G inertia

H energy

J mass

Even the best engines are only about 30% efficient.100kJ of chemical energy would only transfer to 30kJ mechanical and 70kJ heat.

Assuming the chart contains all energy transformations in the Earth system, how much solar radiation goes toward evaporating water?

F 40,000 terajoulesG 92,410 terajoulesH 121,410 terajoulesJ 133,410 terajoules

Bathwater normally has electrolytic behaviors even though distilled water does not. This is because bathwater —

F contains isotopes of hydrogen

G has been heated

H is separated into H+ and OH– ions

J contains dissolved minerals

The chemical equation shows CaCO3 being heated. Which of these statements best describes the mass

of the products if 100 g of CaCO3 is heated?

A The difference in the products’ masses is equal to the mass of the CaCO3.

B The sum of the products’ masses is less than the mass of the CaCO3.

C The mass of each product is equal to the mass of the CaCO3.

D The sum of the products’ masses equals the mass of the CaCO3.

Why is the sum of the products’ energy in thisreaction less than the sum of the reactants’energy?

A Energy is given off as heat.B The products absorb available energy.C Energy is trapped in the reactants.D The reactants’ energy is less than themelting point of glucose.

In West Texas and Southern California, high

winds drive turbines that generate electricity.

One advantage that wind energy has over

energy generated from solar cells is that wind

energy —

A is plentiful everywhere

B can be generated at night

C produces cleaner energy

D is free of environmental hazards