chapter 15 energy and work done

Question 1

(i) define energy

(ii) SI unit for energy

Answer 1

(i) the ability to do work

(ii) joule J

Question 2

what are the two conditions for work to be done?

Answer 2

1. a force acts on an object

2. the force moves in the same direction of the object

Question 3

define non- renewable energy and give an example of non renewable energy

Answer 3

energy that is limited and will run out one day. an example is fossil fuels

Question 4

what is fossil fuels and what are the different types of fossil fuels?

Answer 4

fossil fuels are formed by the remains of dead plants and animals, it takes millions of years to form fossil fuels. types of fossil fuels include crude oil, coal and natural gas

Question 5

what are energy conversions in power stations when burning fossil fuels ?

Answer 5

chemical potential energy - heat energy- kinetic energy- electrical energy

Question 6

what are the uses of fossil fuels?

Answer 6

pertrol is a fuel for cars and motorcycles. diesel is fuel for lorries, taxis and buses. kerosene & natural gas can be stored for cooking

Question 7

what is the impact of fossil fuels on the environment?

Answer 7

when burning fossil fuels, CO2 produced and traps heat in the earths atmosphere. melts ice in the north and south poles. global warming also causes unpredictable and destructive weather patterns.

Question 8

define renewable energy and state the examples of renewable energy.

Answer 8

sustainable and can be renewed indefinitely because of the new growth of organisms or unlimited supplies.
biofuels, geothermal, hydroelectric, solar and wind

Question 9

how is biofuels derived and what are the uses of it?

Answer 9

obtained from plant and animal matter like sugar cane and water hyacinth and energy is produced from burning biofuels.
uses: ethanol from water hyacinth and sugar cane can be used as biodiesel for motor vehicles

Question 10

what is the impact of the use of biofuels on the environment?

Answer 10

when burning biofuels, CO2 produced. plants take in CO2 during photosynthesis. if produced as fast as its burnt, partially offset contribution of global warming.

Question 11

how is geothermal energy derived and what are the uses of it?

Answer 11

it is derived from hot rocks from deep underground in volcanic areas, by drilling into the earth, water flowing through the huge water pipes is heated into steam
uses: steam heated from water can be used to heat homes and buildings

Question 12

what are the energy conversions is geothermal power stations?

Answer 12

heat - kinetic energy - electrical energy

Question 13

what impact does geothermal energy have on the environment?

Answer 13

-some companies extract poisonous substances
- like hydrogen sulfide and arsenic
- since it need to be extracted from underground,
buildings around the power stations may sink
> damage to buildings and roads
>flow patterns of rainwater may also be significantly affected

Question 14

how is hydroelectric energy derived and what are the uses of it?

Answer 14

• flow of water from the reservoir turns the blades of a turbine to generate electric energy
• uses: supply electrical energy to households and factories

Question 15

what are the energy conversions in a hydroelectric power station?

Answer 15

gravitational potential energy - kinetic energy - electrical energy

Question 16

what impact does hydroelectric energy have on the environment?

Answer 16

• it does not produce any pollutants
• during the construction of the dams, it can cause extensive flooding in large areas of forests, wildlife habitat and farmland
• also prevents flow of sediments and nutrients down the river > ecosystem greatly affected

Question 17

how is solar energy derived and what are the uses of it?

Answer 17

-energy in sunlight can be directly converted into electrical energy by solar or photovoltaic cells

uses: 1. some solar heaters channel steam to drive a turbine to generate electrical energy
- but photovoltaic cells can directly change sunlight to electrical energy

Question 18

how is wind energy derived and what are the uses of it?

Answer 18

it is derived from rotating one or more turbines

uses: provide electricity for households and research stations especially in remote areas

Question 19

what impact does wind energy have on the environment?

Answer 19

• causes deaths of bats and birds
  -produces low frequency noises including infrasound
  > some people may experience headaches or feel nauseous is exposed to the sound for a long time