8URL1 Elements, Mixtures, Compounds MCAS Review

Elements, Mixtures, Compounds Review

This is an MCAS Question:

Poll

Which of the following best describes a mixture?

• a material that is made up of many molecules

• a substance that can be changed into another substance

• a material that contains two or more substances

• a substance that has been broken down into its smallest parts

What do you need to know to be able to answer the question:

"Which of the following best describes a mixture?"

• A) a material that is made up of many molecules.

• B) a substance that can be changed into another substance.

• C) a material that contains two or more substances.

• D) a substance that has been broken down into its smallest parts.

Open Ended

What do you need to know to be able to answer the question: "Which of the following best describes a mixture?"

All Matter is either a pure substance or a mixture

Pure Substance

all of the units are the SAME

Mixture

the units in the substance are DIFFERENT, or MIXED.

Pure Substances can be broken down more into elements (one type of atom) or compounds (more than one type of atom)

Elements are one type of atom (but some may be in pairs!)

Compounds are different elements that are chemically combined

Chemically combined is shown in the models as touching!

Mixtures...

• You can often see the different substances (like the chocolate chips in the cookie or the noodles in the pasta)

• You can usually separate out the different substances (like the croutons or the m&ms)

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Multiple Choice

• Element

• Compound

• Mixture

Let's try that MCAS Question...

Multiple Choice

Which of the following best describes a mixture?

• a material that is made up of many molecules

• a substance that can be changed into another substance

• a material that contains two or more substances

• a substance that has been broken down into its smallest parts

Let's try another MCAS Question!

Multiple Choice

Which of the following diagram best represents two different elements combining to form a compound?

Some common compounds you should know

• Salt (NaCl)

• Water (H₂O)

• Methane (NH₄)

• Ammonia (NH₃)

• Sugar (C₁₂H₂₂O₁₁)

• Rust (Fe₂O₃)

Some common mixtures you should know:

• Air (many different gases)

• Chocolate milk (hard to separate, but if it sits, the chocolate goes to the bottom. That's why you have to shake it!)

• Seawater (salt and water)

• Coffee and Cream

Let's try a couple more...

Multiple Choice

Which of the following is a mixture rather than a compound

• oxygen & nitrogen in air

• sodium & chlorine in salt

• hydrogen & oxygen in water

• nitrogen & hydrogen in ammonia

Multiple Choice

Which of the following do water (H₂O), rust (Fe₂O₃), and salt (NaCl) have in common?

• Water, rust, and salt are atoms

• Water, rust, and salt are mixtures

• Water, rust, and salt are elements

• Water, rust, and salt are compounds

Remember the periodic table?

Elements are listed on the Periodic Table

All elements have a Chemical Symbol (an abbreviation or short form)

• The Chemical symbol ALWAYS has a capital letter

• The Chemical Symbol sometimes has a lower case letter too!

Compounds have more than one element Chemically combined.

• That is shown in the Chemical Formula.

• You know it's a compound because there is more than one Upper Case Letter.

• Example:

• Co is the element Cobalt (one upper case letter)

• CO is a compound of Carbon and Oxyten (both letters are upper case)

Molecules are any atoms that are bonded together.

• Elements can be atoms (like Fe) or molecules (like O₂ or N₂)

• Compounds are always molecules

The smallest version of a compound is one molecule. If you break a compound into its elements, it no longer has the properties of the compound.

For example - if you break down your last molecule of salt into Na and Cl, you have two different things - not salt!

Let's try a couple more MCAS Questions!

Multiple Choice

Sucrose (C₁₂H₂₂O₁₁) is also known as table sugar. What is the smallest unit of sugar that maintains the chemical properties of sugar?

• an atom

• an element

• a grain

• a molecule

Multiple Choice

A student makes a ball and stick model of a propane molecule shown here. The black balls represent carbon atoms and the white balls represent hydrogen atoms.

Based on the model, what is the chemical formula of propane?

• C₃H₈

• C₃H₁₀

• 3CH

• 3CH₈

Multiple Choice

Last one! Methane and propane are two compounds that are composed of only carbon and hydrogen atoms. The table shows some of the properties of these two compounds. Which of the following conclusions is best supported by the information in the table

• When two elements combine, the mass of each element changes

• When two compounds are mixed, the state of matter of the mixture changes.

• Two elements can combine to produce different substances with different properties.

• Two compounds can be mixed together to produce different materials with different properties.

Great Job!

Write the vocabulary words and definitions in your notebook!

• atom - the smallest particle of an element

• chemical bond - an attraction between atoms that holds them together in space

• chemical formula - a shorthand representation of an element or compound using chemical symbols

• chemical symbol - a set of characters (letters) that are used to represent an element

• compound - a substance that consists of 2 or more elements combined in a set ratio

Write the vocabulary words and definitions in your notebook!

• element - a pure substance that cannot be broken down chemically

• matter - anything that has mass and takes up space

• mixture - two or more substances that are together, but not chemically combined

• molecule - two or more atoms chemically combined OR smallest particle of a substance and is composed of one or more atoms

• Periodic Table - a table of chemical elements arranged in order of atomic number