Periodic Table

Fill in the blank. The Periodic Table is organized by ______, which tells you how many electron shells the element has.

• periods

• groups

• atomic number

Answer explanation

The Periodic Table is organized by periods, which indicate the number of electron shells an element has. Each row corresponds to a different period, showing how many shells are present in the atoms of the elements.

Fill in the blank. The Periodic Table is organized by ______, which have similar physical and chemical properties, shown in different colors.

• periods

• groups

• families

Answer explanation

The Periodic Table is organized by groups, which are vertical columns containing elements with similar physical and chemical properties. These groups are often color-coded for easy identification.

Fill in the blank. The Periodic Table is organized by ______, which all have the same number of valence electrons (outer electrons).

• groups

• periods

• families

Answer explanation

The Periodic Table is organized by groups, which are vertical columns where elements share the same number of valence electrons. This similarity in valence electrons leads to similar chemical properties among the elements in a group.

Milk spoiling- Is this a physical or chemical change?

• physical change

• chemical change

Answer explanation

Bread turning moldy is a chemical change because it involves the growth of mold, which alters the chemical composition of the bread. This process cannot be reversed, distinguishing it from a physical change.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Water melting- Is this a physical or chemical change?

• physical change

• chemical change

Answer explanation

A melting snowman is a physical change because it involves a change in state from solid (snow) to liquid (water) without altering the chemical composition of the substance.

Tags

NGSS.MS-PS1-4

Hydrogen bonds with nitrogen to make ammonia (NH₃). Is this a physical or chemical change?

• physical change

• chemical change

Answer explanation

The formation of ammonia (NH3) from hydrogen and nitrogen involves a chemical reaction where bonds are broken and formed, resulting in new substances. Therefore, this is a chemical change.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

Sugar being stirred in water - Is this a physical or chemical change?

• Physical change

• Chemical change

Answer explanation

Stirring sugar in water is a physical change because the sugar dissolves but retains its chemical identity. No new substances are formed, and the process is reversible.

Tags

NGSS.MS-PS1-2

What is true about the Law of Conservation of Mass? Select all that apply.

• matter is not created.

• matter is not destroyed.

• there are the same number of atoms before and after the reaction, they just rearrange.

• all of the atoms that are present at the start of the reaction are present at the end.

Answer explanation

The correct choice is 'All of the statements are true.' because all the other statements accurately reflect the Law of Conservation of Mass, which states that matter is neither created nor destroyed in a chemical reaction.

Tags

NGSS.MS-PS1-5

150 grams of magnesium reacts completely with 51 grams of nitrogen gas and creates magnesium nitride. Using what you know about the Law of Conservation of Mass, how much magnesium nitride is produced?

• 51 grams

• 99 grams

• 151 grams

• 201 grams

Answer explanation

According to the Law of Conservation of Mass, the total mass of reactants equals the total mass of products. 150g (Mg) + 51g (N2) = 201g of magnesium nitride produced.

Tags

NGSS.MS-PS1-5

Which family is made up of elements that are 1) hard and shiny, 2) good conductors of electricity, 3) malleable and ductile?

• metals

• nonmetals

• semimetals

Answer explanation

The correct choice is metals, as they are characterized by being hard, shiny, good conductors of electricity, and are malleable and ductile. Nonmetals and semimetals do not share all these properties.