apes 6.6-6.8

The half-life of carbon-14 is 5715 years. If an animal bone contains 20 grams of carbon-14 when the animal dies, how many grams of carbon-14 will be left in 17145 years?

2.5

A 2.5 gram sample of an isotope of Strontium-90 was formed in a 1960 explosion of an atomic bomb at Johnson Island in the Pacific Test Site. The half-life of Strontium-90 is 28 years. In what year did only 0.625 grams of this Strontium-90 remain?

2016

A sample of radioactive waste has a half-life of 10 years and an activity level of 2 curies. After how many years will the activity level of this sample be 0.25 curie?

30 years

An isotope of Cesium-137 has a half-life of 30 years. If 35.0 mg of Cesium-137 disintegrates over a period of 90 years, how many mg of Cesium-137 would remain?

4.375

After 200 million years, only 1/16 of the original amount of a particular radioactive waste will remain. The half-life of this radioactive waste is how many million years?

50 million years

If the half-life of Francium-233 is 22 minutes, how much time must elapse in order for 60 grams of a 64 gram sample to undergo decay? In other words, after how many minutes will you only have 4 grams of the original isotope remaining?

88 mins

A developer intends to use passive solar heating in a new construction project in Minnesota in an effort to reduce electricity costs for the property owners. What should be employed to maximize the benefit of passive solar heating?

Install south-facing glazed windows in the home and dark surfaces to cover the walls and floors

Describe how electricity is generated using photovoltaic cells.

Photons of light excite electrons that result in a flow of current.

What is a disadvantage of using nuclear energy as a source of electricity?

Spent fuel rods are difficult and expensive to dispose of

What is a negative consequence associated with photovoltaic solar cells?

The manufacture of photovoltaic solar cells involves toxic metals that can be released into the environment

passive solar energy

absorb heat directly from the sun without the use of mechanical and electric equipment, and energy cannot be collected or stored

Photovoltaic solar cells

capture light energy from the sun and transform it directly into electrical energy. Their use is limited by the availability of sunlight

What is a drawback to using biofuels, such as ethanol, as a fuel source?

energy investment needed for ethanol is high

What process would provide the energy used to generate electricity at a power plant?

fission

Describe an advantage of burning biomass rather than burning fossil fuels in developing countries?

it is cheaper than fossil fuel extraction making it more readily available for use

Buildings designed to partially heat rooms by passive solar heating rely on what?

materials that can absorb solar energy to warm the room

What was the primary cause for the decline in the use of wood as a fuel in the eighteen hundreds?

reduced wood availability due to widespread deforestation

What is a major limitation of using photovoltaic cells to generate electricity?

they don't produce as much electricity on cloudy days

Some solar energy systems produce high-temperature water for industrial applications and produce steam to run turbines that generate electricity. What type of solar energy system is needed for these kinds of applications?

use a solar collector system using mirrors or lenses to concentrate sunlight

active solar energy

use solar energy to heat a liquid through mechanical and electric equipment to collect and store the energy captured from the sun

Throughout the world, especially the less-developed countries, burning wood or other biomass for heating or cooking in homes is common. One negative environmental impact of this practice is the production of particulates indoors, which can be a health hazard to humans.What is the best strategy for mitigating this potential problem?

ventilation

The water used in a nuclear power plant is often released back into a reservoir. What effects could this released water have on the reservoir?

water warms up which decreases dissolved oxygen levels