Science review

Antonella inflates a balloon and notices it changes the shape. What does this show about gases?

• They do not take up space

• They have mass and take up space

• Only solids and liquids are matter

• Gases are weightless

Answer explanation

When Antonella inflates the balloon, the air (a gas) spreads out inside, changing the shape of the balloon to match the gas’s volume. This shows that gases:

• Do not have a fixed shape (they adapt to the container they are in).

• Can be compressed or expanded depending on the space available.

Lyla melts butter to make pancakes. What kind of change is happening?

• Physical property

• Magnetic change

• Physical change

• Chemical change

Answer explanation

When Lyla melts butter to make pancakes, a physical change is happening. This is because melting only changes the state of the butter from solid to liquid, without altering its chemical composition.

Jeronimo finds a shiny, silver-gray piece of metal and realizes it is iron. He learns that iron cannot be broken down into simpler substances.

What type of material is iron?

• A mixture

• A compound

• An element

• A molecule

Answer explanation

Iron is classified as an element because it cannot be broken down into simpler substances through chemical means. It is made up of only one type of atom.

Carpio picks up a large pumpkin and feels it is heavy. What property is he noticing?

• Volume

• Physical property

• Mass

• Hardness

Answer explanation

EXPLANATION

Carpio is noticing the mass of the watermelon or pumpkin because the sensation of heaviness is directly related to the amount of matter in an object.

Remember: Mass is a measure of the total amount of matter in an object, and it is what gives an object its weight in a gravitational field.

When Carpio feels that the watermelon or pumpkin is heavy, he is experiencing the effect of its mass due to Earth's gravity pulling on it.

Laura pours water onto the sand at the beach. It spreads but keeps its volume. What state of matter is it?

• Solid

• Liquid

• Gas

• Plasma

When iron is exposed to air and moisture, it forms rust. What type of change is this?

• Physical, because it only changes appearance.

• Chemical, because a new substance is formed.

• Nuclear, because the atoms are destroyed.

• Physical, because the iron remains the same.

Answer explanation

Rusting involves the reaction of iron with oxygen and water, leading to the formation of new substances, primarily hydrated iron oxide. This process changes the chemical composition of iron and results in the formation of brittle and flaky rust. Since new compounds are formed, this is classified as a chemical change

Which of the following is an example of a chemical property?

• The color of gold

• The hardness of a diamond.

• The melting point of ice.

• The ability of wood to burn.

Answer explanation

A chemical property describes the ability of a substance to undergo a chemical change, which results in the formation of new substances.

The ability of wood to burn is a chemical property because it involves combustion, a chemical reaction where wood reacts with oxygen to produce ash, carbon dioxide, and water.

This process changes the chemical composition of the wood, making it a chemical property

Ms Anna asks students to find the density of an object Which formula should they use?

• Mass divided by volume

• Volume multiplied by mass

• Mass plus volume

• Mass minus volume

Answer explanation

To find the density of an object, students should use the formula:

This formula calculates how much mass is contained in a specific volume of the objec

A chef boils pasta in water. After cooking, the water level has decreased. What happened to the missing water?

• It turned into a new substance.

• It chemically bonded with the pasta.

• It evaporated into the air.

• It was absorbed by the pasta.

Answer explanation

When the chef boils pasta in water, the heat from boiling causes some of the water to change from a liquid to a gas state, a process known as evaporation. This is why the water level decreases.

Hanna mixes lettuce, tomatoes, cucumbers, and carrots to make a salad.

What has she created?

• A compound

• An element

• A mixture

• A molecule

Answer explanation

Hanna has created a mixture when she combines lettuce, tomatoes, cucumbers, and carrots to make a salad. This is because the components of the salad remain chemically unchanged and can be separated again by physical means.