Flashcard de vocabular TOEFL

Definition: The process by which one thing absorbs or is absorbed by another

Example sentences:

• Milk appeared to inhibit the antioxidant potential of the flavonoids, reducing their absorption into the bloodstream

An acid is a chemical substance that has a pH value of less than 7. An alkali is a chemical substance that has a pH value of more than 7. There are many acids and alkalis. For example:

• Vinegar in a salad is an acid
• Vitamin C is an acid
• Salt is an alkali.
• Sodium is one of the alkali metals.

To describe acid and alkali, we can use the adjectives ‘acidic’ and ‘alkaline’.

The adjective “acidic” describe something containing an acid and having a pH less than 7. Here are example sentences:

• The water in a polluted lake is acidic
• Carbon dioxide is acidic.
• When an acid is dissolved in water we get an acidic solution.

The adjective “alkaline” describe something containing an alkali and having a pH greater than 7. Here are example sentences:

• Water can become alkaline as it seeps through rocks, picking up minerals such as calcium and magnesium.
• Alkaline chemicals can be harmful to our bodies.

Acidity refers to the quality or state of being acidic. It can describe a chemical property of a substance, such as the pH level, or a sharp and tangy taste. Acidity is also used metaphorically to describe a tone or attitude that feels sharp or biting. 

• The acidity of the lemon makes it perfect for cleaning stains.

• Too much acidity in the soil can harm plant growth.

• Her comment had a tone of acidity that surprised everyone.

Definition: the medieval forerunner of chemistry, based on the supposed transformation of matter. It was concerned particularly with attempts to convert base metals into gold or to find a universal elixir.

Example sentences:

• In the second decade of the twenty-first century, alchemy is not only about the transmutation of metals, but the shift in consciousness that returns us from the physical to the non-physical.
• Throughout its history, alchemy has shown a dual nature. On the one hand, it has involved the use of chemical substances and so is claimed by the history of science as the precursor of modern chemistry.

An acid is a chemical substance that has a pH value of less than 7. An alkali is a chemical substance that has a pH value of more than 7. There are many acids and alkalis. For example:

• Vinegar in a salad is an acid
• Vitamin C is an acid
• Salt is an alkali.
• Sodium is one of the alkali metals.

To describe acid and alkali, we can use the adjectives ‘acidic’ and ‘alkaline’.

The adjective “acidic” describe something containing an acid and having a pH less than 7. Here are example sentences:

• The water in a polluted lake is acidic
• Carbon dioxide is acidic.
• When an acid is dissolved in water we get an acidic solution.

The adjective “alkaline” describe something containing an alkali and having a pH greater than 7. Here are example sentences:

• Water can become alkaline as it seeps through rocks, picking up minerals such as calcium and magnesium.
• Alkaline chemicals can be harmful to our bodies.

Acidity is the level of acid in substances. Likewise, alkalinity is the level of alkali in substances. You can ‘increase/decrease the acidity/alkalinity’.

Here are example sentences:

• The pollution produced by carbon dioxide increases the acidity of the oceans and affects the marine food chain.
• We can decrease the alkalinity by adding more acidic chemicals.

Definition: The chemical element of atomic number 13, a light silvery-grey metal.

Example sentences:

• Officials said materials made of plastic, aluminum, glass and metals will have to be recycled.

An atom is the smallest amount of a substance that can take part in a chemical reaction.

Definition: CO2

Example senences:

• Plants give out oxygen and animals expel carbon dioxide and methane.

Definition: A salt of the anion CO32-, typically formed by reaction of carbon dioxide with bases.

Example sentences:

• The reaction with carbonates gives the nitrate salt, water, and carbon dioxide. In natural water systems, many common minerals are formed by anion substitution-precipitation reactions, among them carbonates, phosphates, and the sulfate-containing rocks.

Definition: A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change

Example senences:

• Chlorine acts as a catalyst promoting the breakdown of ozone

Definition: A thing that is composed of two or more separate elements; a mixture;A substance formed from two or more elements chemically united in fixed proportions

Example sentences:

• The air smelled like a compound of diesel and petrol fumes. The layers of plants and animals slowly broke down into simple substances called hydrocarbons, compounds of hydrogen and carbon.

To change from a gaseous state into a liquid state, we can use the verb ‘condense’. Here are example sentences:

• The cooler temperatures cause the gas to condense into a liquid.​
• The steam from the shower condenses quickly when it hits the cool window.

Definition: The process of corroding or being corroded

Example senences:

• This is because the iron electrode is more susceptible to corrosion and to self-discharge on standing.

Stronger acids with a lower ph values are corrosive. This means they can attack metals and destroy skin if spilled.

When a substance dissolves, it means it disappears - it mixes with a liquid and becomes part of the liquid. For example:

• Sugar dissolves in water.

You can also say “Water dissolves sugar.” So “sugar dissolves in water” or “water dissolves sugar.”

A metal that is ductile is able to be deformed without losing toughness. An example in a sentence:

• Unlike brittle elements such as sulfur, metal is highly ductile.

To change from a liquid state into a gaseous state, we can use the verb ‘evaporate’. ‘Evaporate’ is an intransitive verb as well. For example:

• The warmer temperatures cause the liquid to evaporate into a gas.​
• Water evaporates rapidly in hot weather.

Definition: Relating to or involving evaporation

Example sentences:

• In the early 19th century, other methods of cooling were explored, and several evaporative refrigerators were patented, although it was another half-century before they made an impact on the food industry.

Definition: Easily set on fire

Example sentences:

• Kerosene is volatile, flammable and leaks very easily from containers.

Definition: Relating to or having the characteristics of a gas

Example sentences:

• gaseous emissions from motor vehicles.

Definition: Convert (a solid or liquid, especially coal) into gas:

Example sentences:

• The plans, which will be carried out over a 20 year horizon, will include energy recovery techniques such as incineration and gasification

Definition: Convert (a solid or liquid, especially coal) into gas

Example sentences:

• Coal, too, could be made carbon-free, using advanced power plants that gasify the fuel and then generate power while stripping away the carbon for sequestration underground.

Definition: A colourless, odourless, highly flammable gas, the chemical element of atomic number 1.

Example sentences:

• We know that the Moon is low on certain chemicals such as hydrogen and carbon

Definition: A constituent which impairs the purity of something

Example sentences:

• The impurities dissolve in lead and evaporate leaving behind silver and gold. Aluminium and lead are impurities frequently found in tap water.

A substance that is malleable is soft and can easily be made into different shapes. An example in sentence:

• Silver is the most malleable of all metals.

Definition: Chemical formula: CH4

Example sentences:

• Trace gases include methane, nitrous oxide, carbon monoxide, sulphur dioxide, and ozone

A microscope is a scientific instrument which makes very small objects look bigger so that more detail can be seen.

Definition: Relating to or consisting of molecules

Example sentences:

• Fire is actually a dancing plasma of molecules and molecular fragments, excited into a glowing state by heat.

A molecule is the smallest amount of a chemical substance which can exist by itself.

Definition: The condition of being chemically or electrically neutral

Example sentences:

• A sodium ion was introduced into the system to reach overall electrical neutrality.

Definition: Make (an acidic or alkaline substance) chemically neutral:

Example sentences:

• Baking soda, a gentle alkaline powder, neutralizes odor-causing acids by restoring your skin's natural pH level.

A neutron is an atomic particle that has no electrical charg

Definition: The chemical element of atomic number 7, a colourless, odourless unreactive gas that forms about 78 per cent of the earth’s atmosphere

Example sentences:

• The data demonstrate that nitrogen and phosphorus are in especially short supply.

The nucleus of an atom or cell is the central part of it.

Definition: A distinctive smell, especially an unpleasant one

Example sentences:

• During that time, the officer had smelled the odour of alcohol on the accused's breath.

Definition: A table of the chemical elements arranged in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns.

Example sentences:

• When you move down the periodic table, as the atomic numbers increase, the elements become rarer

A proton is an atomic particle that has a positive electrical charge.

Definition: a reply; a change that occurs when substances are mixed

Example sentences:

• Scientists explore the origins of energy in chemical reactions using experimental quantum chemistry.
• Reactions in solids tend to be much more complex than those in liquids, where molecules quickly diffuse into a uniform mixture.

Definition: Remove impurities or unwanted elements from (a substance), typically as part of an industrial process

Example sentences:

• Sugar was refined by boiling it in huge iron vats.
• When oil is refined this reaction is used to remove unwanted alkenes.

Definition: Cause (something) to become thoroughly soaked with liquid so that no more can be absorbed:

Example sentences:

• The soil is saturated

We can use the noun solubility to describe the character of a substance as being soluble. So in your the listening part you may hear a sentence like this:

• One characteristic of sugar is its solubility in water.

Note:  The solubility of a substance can be high or low, or in some cases even infinite. Most substances, however, have a maximum solubility.

If we want to use an adjective to describe a substance that can dissolve, we use the adjective ‘soluble’. Likewise, to describe a substance that cannot dissolve, we use the adjective ‘insoluble’. Here are example sentences:

• Salt is soluble in water = Salt can dissolve in water.
• Sand is insoluble in water = Sand cannot dissolve in water

When a substance dissolves in a liquid, we say that the substance is a solute, and the liquid is a solvent. The mixture of the solvent and the solute is called a solution.

When a substance dissolves in a liquid, we say that the substance is a solute, and the liquid is a solvent. The mixture of the solvent and the solute is called a solution. 

To change from a solid state into a gaseous state, we can use the verb “sublimate”.  Sublimating is the process of sublimating. For example:

• Ice can sublimate at temperatures below freezing.
• During sublimation, solids are transformed directly to vapor without passing through a liquid stage.

To change from a solid state into a gaseous state, we can use the verb “sublimate”.  Sublimating is the process of sublimating. For example:

• Ice can sublimate at temperatures below freezing.
• During sublimation, solids are transformed directly to vapor without passing through a liquid stage.

Definition: A colourless pungent toxic gas formed by burning sulphur in air.

Example sentences:

• When fossil fuels burn, carbon dioxide, sulfur dioxide, nitrogen oxides, sooty particles, dioxins, and other pollutants are released into the air and water.

Definition: Containing sulphur or sulphuric acid

Example sentences:

• the sulphuric by-products of wood fires.

Definition: the combination of ideas into a complex whole

Example sentences:

• Blacks and other minorities have higher concentrations of melanin, which makes their skin darker, but this inhibits synthesis of vitamin D, the researchers explained.
• Now, biologists know that RNAs serve many other essential functions: they help with protein synthesis, control gene activity and modify other RNAs.

Definition: (Of a substance) made by chemical synthesis, especially to imitate a natural product

Example senences:

• Mixtures of several synthetic dyes, or mixtures of natural and synthetic dyes, could produce more subdued colors.

Definition: The chemical element of atomic number 92, a gray, dense radioactive metal used as a fuel in nuclear reactors. (Symbol: U)

Example sentences:

• It is not certain if the effects are due to the chemical or the radioactive properties of uranium.

When a liquid like water becomes a visible, gas-like substance floating in the air, it's a vapor. Examples of vapor are fog and mist.

The verb ‘vaporize ’means to change into vapor or to cause something to change into vapor.  For example:

• Boiling water vaporizes and rises into the atmosphere.
• Heat is used to vaporize a liquid.

Definition: (Of a substance) easily evaporated at normal temperatures

Example senences:

• Even small amounts of gasoline or other volatile fuels or solvents mixed with kerosene can substantially increase the risk of a fire or an explosion.