GED Science Practice Test 4

Your immune system protects you from pathogens, such as viruses and bacteria, that cause disease. When a pathogen enters the body, white blood cells called B cells make antibodies. Antibodies are proteins that attach to the pathogen and help the body destroy it. Some B cells also become memory cells. Memory cells stay in the body for years. If the same pathogen enters the body again, memory cells recognize it and start making antibodies much more quickly.

A vaccine contains a harmless form or a piece of a pathogen. It trains the immune system to recognize the pathogen without causing the disease.

In a study of a new vaccine, 50 adult volunteers received a first dose on day 0 and a second dose, called a booster, on day 60. Researchers measured the amount of antibody in each volunteer's blood every 10 days, in arbitrary units (AU). The graph shows the average for all 50 volunteers. The dashed line marks 100 AU, the level the researchers consider protective.

Your immune system protects you from pathogens, such as viruses and bacteria, that cause disease. When a pathogen enters the body, white blood cells called B cells make antibodies. Antibodies are proteins that attach to the pathogen and help the body destroy it. Some B cells also become memory cells. Memory cells stay in the body for years. If the same pathogen enters the body again, memory cells recognize it and start making antibodies much more quickly.

A vaccine contains a harmless form or a piece of a pathogen. It trains the immune system to recognize the pathogen without causing the disease.

In a study of a new vaccine, 50 adult volunteers received a first dose on day 0 and a second dose, called a booster, on day 60. Researchers measured the amount of antibody in each volunteer's blood every 10 days, in arbitrary units (AU). The graph shows the average for all 50 volunteers. The dashed line marks 100 AU, the level the researchers consider protective.

Measles is a disease caused by a virus. It spreads through the air when an infected person coughs or sneezes, and it is one of the most contagious diseases known. Antibiotics, which kill bacteria, do not work against viruses. The best protection against measles is a vaccine, given in two doses during childhood.

Some people cannot be vaccinated, such as babies younger than 12 months and people whose immune systems are weakened by certain illnesses or medicines. These people can still be protected by herd immunity. When a large share of a community is immune, an infected person is unlikely to meet someone the virus can infect, so the disease cannot spread easily. For measles, health experts estimate that about 95% of a community must be immune.

During one outbreak year, a state health department compared five towns. The chart shows each town's vaccination rate (the percent of residents who were fully vaccinated) and the number of measles cases for every 10,000 residents.

Measles is a disease caused by a virus. It spreads through the air when an infected person coughs or sneezes, and it is one of the most contagious diseases known. Antibiotics, which kill bacteria, do not work against viruses. The best protection against measles is a vaccine, given in two doses during childhood.

Some people cannot be vaccinated, such as babies younger than 12 months and people whose immune systems are weakened by certain illnesses or medicines. These people can still be protected by herd immunity. When a large share of a community is immune, an infected person is unlikely to meet someone the virus can infect, so the disease cannot spread easily. For measles, health experts estimate that about 95% of a community must be immune.

During one outbreak year, a state health department compared five towns. The chart shows each town's vaccination rate (the percent of residents who were fully vaccinated) and the number of measles cases for every 10,000 residents.

Washing hands is one of the simplest ways to stop the spread of disease-causing bacteria and viruses. A student designed an experiment to compare handwashing methods.

Twenty-five volunteers each touched the same door handle. Then each volunteer was assigned one of five treatments, with five volunteers for each treatment. Right after the treatment, each volunteer pressed the fingertips of one hand onto a sterile agar plate, a dish of gel on which bacteria can grow. All plates were sealed and kept at 37 °C for 48 hours. Then the student counted the bacterial colonies on each plate. Each colony is a visible spot that grew from bacteria left on the fingertips.

Every volunteer used water from the same tap at the same temperature and dried their hands with a new paper towel.

Washing hands is one of the simplest ways to stop the spread of disease-causing bacteria and viruses. A student designed an experiment to compare handwashing methods.

Twenty-five volunteers each touched the same door handle. Then each volunteer was assigned one of five treatments, with five volunteers for each treatment. Right after the treatment, each volunteer pressed the fingertips of one hand onto a sterile agar plate, a dish of gel on which bacteria can grow. All plates were sealed and kept at 37 °C for 48 hours. Then the student counted the bacterial colonies on each plate. Each colony is a visible spot that grew from bacteria left on the fingertips.

Every volunteer used water from the same tap at the same temperature and dried their hands with a new paper towel.

Cystic fibrosis (CF) is an inherited disease. It causes thick, sticky mucus to build up in the lungs, which makes lung infections more likely. CF is caused by a recessive allele, f. The normal allele, F, is dominant.

• A person with the genotype FF does not have CF.
• A person with the genotype Ff does not have CF but is a carrier: this person can pass the f allele to children.
• Only a person with the genotype ff has CF.

Each parent passes one of their two alleles to each child, by chance.

The pedigree shows three generations of one family. Squares are males, circles are females, and filled shapes are people who have CF. A horizontal line between two people connects a couple; a vertical line leads down to their children.

Cystic fibrosis (CF) is an inherited disease. It causes thick, sticky mucus to build up in the lungs, which makes lung infections more likely. CF is caused by a recessive allele, f. The normal allele, F, is dominant.

• A person with the genotype FF does not have CF.
• A person with the genotype Ff does not have CF but is a carrier: this person can pass the f allele to children.
• Only a person with the genotype ff has CF.

Each parent passes one of their two alleles to each child, by chance.

The pedigree shows three generations of one family. Squares are males, circles are females, and filled shapes are people who have CF. A horizontal line between two people connects a couple; a vertical line leads down to their children.

Sound is a mechanical wave. It moves as vibrations that are passed from particle to particle through a material, called a medium, such as air, water or a solid. Because sound needs particles to vibrate, it cannot travel through empty space (a vacuum).

Two properties of a sound wave affect what we hear:

• Frequency is the number of vibrations (cycles) per second, measured in hertz (Hz). A higher frequency gives a higher pitch.
• Amplitude is the size of the vibration. A larger amplitude gives a louder sound.

The time for one full cycle is the period. The speed of a wave (v), its frequency (f) and its wavelength (\lambda, the length of one full cycle, in meters) are related by the formula

v = f\lambda

In air at room temperature, sound travels at about 340 meters per second (m/s).

A student recorded two musical notes, A and B, with a microphone connected to a computer. The graphs show the first 10 milliseconds (ms) of each recording, drawn on the same scales.

Light is an electromagnetic wave. Unlike sound, electromagnetic waves do not need a medium. They can travel through empty space at about 300,000 kilometers per second (km/s). That is how sunlight crosses the roughly 150,000,000 km between the Sun and Earth.

Visible light is only a small part of the electromagnetic spectrum, shown in the diagram. All of these waves travel at the same speed in space, but they have different wavelengths. The shorter the wavelength, the higher the frequency and the more energy the wave carries.

Higher-energy waves can harm living things. Ultraviolet (UV) light from the Sun can damage the DNA in skin cells. This causes sunburn and raises the risk of skin cancer. X-rays and gamma rays carry even more energy. The same kind of damage can also be useful: some hospitals use lamps that give off UV light to kill bacteria and viruses on surfaces, because damaged DNA stops these microbes from reproducing.

Light is an electromagnetic wave. Unlike sound, electromagnetic waves do not need a medium. They can travel through empty space at about 300,000 kilometers per second (km/s). That is how sunlight crosses the roughly 150,000,000 km between the Sun and Earth.

Visible light is only a small part of the electromagnetic spectrum, shown in the diagram. All of these waves travel at the same speed in space, but they have different wavelengths. The shorter the wavelength, the higher the frequency and the more energy the wave carries.

Higher-energy waves can harm living things. Ultraviolet (UV) light from the Sun can damage the DNA in skin cells. This causes sunburn and raises the risk of skin cancer. X-rays and gamma rays carry even more energy. The same kind of damage can also be useful: some hospitals use lamps that give off UV light to kill bacteria and viruses on surfaces, because damaged DNA stops these microbes from reproducing.

Ammonia (\text{NH}_3) is one of the most important chemicals made by industry. Most of it is used to make fertilizers that help farmers grow food. Factories make ammonia with the Haber process, in which nitrogen gas from the air reacts with hydrogen gas:

nitrogen + hydrogen → ammonia

\text{N}_2 + \text{H}_2 \rightarrow \text{NH}_3 (not balanced)

In this and every chemical reaction, atoms are rearranged but are not created or destroyed. So the total mass of the products equals the total mass of the reactants. This is the law of conservation of mass.

The Haber reaction gives off heat. It is also reversible: as ammonia forms, some of it breaks back down into nitrogen and hydrogen, so the gas mixture leaving the reactor is never 100% ammonia. The graph shows the percent of ammonia in the final gas mixture at different temperatures and pressures (atm = atmospheres).

The reaction is extremely slow at low temperatures, even with an iron catalyst, a substance that speeds up a reaction without being used up. Most ammonia factories run at about 450 °C and 200 atm.

Ammonia (\text{NH}_3) is one of the most important chemicals made by industry. Most of it is used to make fertilizers that help farmers grow food. Factories make ammonia with the Haber process, in which nitrogen gas from the air reacts with hydrogen gas:

nitrogen + hydrogen → ammonia

\text{N}_2 + \text{H}_2 \rightarrow \text{NH}_3 (not balanced)

In this and every chemical reaction, atoms are rearranged but are not created or destroyed. So the total mass of the products equals the total mass of the reactants. This is the law of conservation of mass.

The Haber reaction gives off heat. It is also reversible: as ammonia forms, some of it breaks back down into nitrogen and hydrogen, so the gas mixture leaving the reactor is never 100% ammonia. The graph shows the percent of ammonia in the final gas mixture at different temperatures and pressures (atm = atmospheres).

The reaction is extremely slow at low temperatures, even with an iron catalyst, a substance that speeds up a reaction without being used up. Most ammonia factories run at about 450 °C and 200 atm.

Lime (calcium oxide, CaO) is used to make cement, steel and glass and to treat drinking water. At a lime plant, the process has several steps:

1. Large rocks of limestone (calcium carbonate, \text{CaCO}_3) are crushed into smaller pieces.
2. The pieces are heated in a kiln to about 900 °C. The heat breaks the calcium carbonate down into calcium oxide and carbon dioxide gas: \text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2. This reaction continues only while heat is supplied.
3. The carbon dioxide gas leaves the kiln through a tall stack.
4. The lime is cooled and ground into a fine powder.
5. Some lime is mixed with water. The lime and water react to form a new substance, calcium hydroxide (slaked lime). This reaction gives off so much heat that some of the water boils.

Lime plants release large amounts of carbon dioxide, both from the reaction in the kiln and from burning fuel to heat the kiln.

Our solar system has eight planets that orbit the Sun. The four inner planets (Mercury, Venus, Earth and Mars) are small and rocky. The four outer planets (Jupiter, Saturn, Uranus and Neptune) are much larger and are made mostly of gases and ices.

Distances in the solar system are often measured in astronomical units (AU). One AU is the average distance from Earth to the Sun, about 150 million kilometers. A planet's orbital period is the time it takes to travel once around the Sun.

*The outer planets have no solid surface; these values are for the top of the clouds.

An object's weight on a planet, in newtons (N), can be found with W = mg, where m is the object's mass in kilograms and g is the planet's surface gravity in m/s².

The bar graph shows the average temperature at each planet's surface (or cloud tops).

Our solar system has eight planets that orbit the Sun. The four inner planets (Mercury, Venus, Earth and Mars) are small and rocky. The four outer planets (Jupiter, Saturn, Uranus and Neptune) are much larger and are made mostly of gases and ices.

Distances in the solar system are often measured in astronomical units (AU). One AU is the average distance from Earth to the Sun, about 150 million kilometers. A planet's orbital period is the time it takes to travel once around the Sun.

*The outer planets have no solid surface; these values are for the top of the clouds.

An object's weight on a planet, in newtons (N), can be found with W = mg, where m is the object's mass in kilograms and g is the planet's surface gravity in m/s².

The bar graph shows the average temperature at each planet's surface (or cloud tops).

Our solar system has eight planets that orbit the Sun. The four inner planets (Mercury, Venus, Earth and Mars) are small and rocky. The four outer planets (Jupiter, Saturn, Uranus and Neptune) are much larger and are made mostly of gases and ices.

Distances in the solar system are often measured in astronomical units (AU). One AU is the average distance from Earth to the Sun, about 150 million kilometers. A planet's orbital period is the time it takes to travel once around the Sun.

*The outer planets have no solid surface; these values are for the top of the clouds.

An object's weight on a planet, in newtons (N), can be found with W = mg, where m is the object's mass in kilograms and g is the planet's surface gravity in m/s².

The bar graph shows the average temperature at each planet's surface (or cloud tops).

Sunspots are dark patches on the Sun's surface. They look dark because they are cooler than the surface around them. They form where the Sun's magnetic field is very strong. The number of sunspots rises and falls in a repeating pattern called the solar cycle. Years with the most sunspots are called solar maximum, and years with the fewest are called solar minimum.

When there are many sunspots, the Sun also produces more solar storms: bursts of radiation and clouds of electrically charged particles. When these reach Earth, they can disrupt radio signals, GPS and satellites, damage power grids, and cause bright auroras (the northern and southern lights). Auroras are usually seen only near the North and South Poles, but during strong solar storms they can be seen much farther from the poles.

The graph shows the average number of sunspots observed each year from 1996 to 2024. The values are rounded and based on public records from the Royal Observatory of Belgium.

Sunspots are dark patches on the Sun's surface. They look dark because they are cooler than the surface around them. They form where the Sun's magnetic field is very strong. The number of sunspots rises and falls in a repeating pattern called the solar cycle. Years with the most sunspots are called solar maximum, and years with the fewest are called solar minimum.

When there are many sunspots, the Sun also produces more solar storms: bursts of radiation and clouds of electrically charged particles. When these reach Earth, they can disrupt radio signals, GPS and satellites, damage power grids, and cause bright auroras (the northern and southern lights). Auroras are usually seen only near the North and South Poles, but during strong solar storms they can be seen much farther from the poles.

The graph shows the average number of sunspots observed each year from 1996 to 2024. The values are rounded and based on public records from the Royal Observatory of Belgium.